Still overheating

[NSXTech]

Good point. But I am told that the Ron Davis radiator interefers with the Type R brace given the lower positioning of the radiator hose .......... as we solve one problem we seem to encounter another, so much for mother Honda listening to our pleas ...... :wink:

Davis will make their radiator to fit any config. Its only about another 100. over the price of their 'custom' NSX radiator to make changes, such as lower hose clearance, or tank position. For me its easy, I just drive on over and show em what I need. For those of you not in SUNNY Phoenix, I'm sure a phone call to them will guide you thru the custome order process. They do make the highest quality radiators under 500. I have ever seen.

MB

 

[zahntech]

As per the diagnostic flow chart for Code 22 if there is no oil pressure or low oil pressure at the front oil pressure switch at certain RPMs the spoilvalve opperation is to be checked and is a possible cause for code 22 to be set..JZ

 

[NSX-Racer]

As per the diagnostic flow chart for Code 22 if there is no oil pressure or low oil pressure at the front oil pressure switch at certain RPMs the spoilvalve opperation is to be checked and is a possible cause for code 22 to be set..JZ

Thanks, I will let my mechanic check all these items once again (including spoil valve and pressure switch of course) and then we'll be working on a solution to check the oil pressure at this cylinder bank under real life conditions (which is not easy because we have no racetrack in front of the shop - would be better if we build one in the long run :wink: ).

Too bad that this CEL didn't come up during the multiple hot dyno runs before the last event (where the engine lastly did make consistent 306 hp at the crank without any overheating etc.).

 

[NSX-Racer]

I would hook up a pressure guage with whip hose and read it from inside the car while driving, as opposed to on the dyno.

Mark, as this will be our next action I need one more info that I couldn't find in the manual: How much minimum oil pressure is needed to open the pressure switch for the Vtec? (I ask this because probably there's a mechanical problem with the switch, the electronic side seems to be fine).

 

[FIGHTERCAR]

Do you have a heat shield between your front exhaust header and the oil pan?

That exhaust is at least 1000 degrees at full power and it radiats right on your oil pan. The oil gets hot and then it gets thin.

Either wrap your header pipe or build a stainless steel heat shield between the pipe and the pan.

 

[NSX-Racer]

Thanks, Fightercar, sounds reasonable, I will tell my techie. BTW: I have still no answer to my previous question:
How much minimum oil pressure is needed to open the pressure switch for the Vtec?

Now that's for real experts :wink:

 

[zahntech]

The exact pressure at wich the switch opens I cannot tell you, however according to the Diagnostic flow chart for the pressure switch, at 5000rpm there must be a min of 57psi/392kpa at the switch

 

[NSXTech]

Sorry NSX-RACER, I was out of town, not ignoring the question. The pressure should be 57psi @5k rpm as zt pointed out. My experience from doing this test shows numbers as low as 50psi with no cel. Viscosity, heat, etc will effect this pressure so the exact number you should see is hard to say. As long as you have over 50, you should be okay.

However, just as important, and just as likely (maybe more so) to cause the cel, is pressure when there should not be. If the ecu sees pressure at the switch when the spool valve is closed; i.e. a sticky or dirty spool or bore, that will cause the same cel. When you hook up the pressure guage, you should see no more than 5-7 psi @3k with valve closed. If you want to do a quick pressure check in the shop, you can apply battery voltage to the single wire at the spool valve (harness disconnected) and check pressure at 5k rpm as well as with valve closed. As I mentioned earlier, I would highly reccomend doing this test dynamically if possible to eliminate heat, windage, etc.

HTH,
MB

 

[NSX-Racer]

Thanks Zahntech and Larry! Just to be clear, Larry: this 5 to 7 PSI should be measured at 3000 rpm at the same place where I should have above 50 at 5000 or are you writing about the lines behind the pressure switch?

Just to add the info: The CEL always came when I just floored the throttle and entered Vtec rpm range, not in low rpms. BTW: It's high time that you come over and take things in your hand :biggrin:

 

[zahntech]

Yes same access port on cyl head.. :smile:







BTW NSXTech=Mark :smile:

 

[NSX-Racer]

BTW NSXTech=Mark :smile:

Ooops, sorry, Mark - seems that not only my engine has some internal problems - I should check the internal brain pressure switch too...

 

[godspeed01]

head gasket. Just cause you changed it does not mean it didnt crack or leak again. After all you are driving car under race conditions.

if it is smoking white when you turn on the car there is coolant getting in the cylinders some how. Bet you a dollar the head was not torqed down right or the head bolt worked its way lose..... or the head bolts where not replaced with new ones and torqued down to the right specs. Need to replace the bolts every time you take off the head unless you use APR head bolts.

you have super heated gas coming through one of the cylinders and it is super heating your coolant. head bolts need to be check for proper torque after driving then for a while from a fresh rebuild.

Had my MR2 over heat before dude to HG... it was a some of a *itch to deal with. I didnt have a garage and still dont so i didnt have place to rebuild so i poured some head gasket sealer into the coolant and let the car run that way. That stuff is suppost to turn to glass at higher temperatures to "seal" the leak. This tempory solution but i have hear of people driving their cars for years... and i have to say my MR2 had good results. But you race, so get your system presure tested for a few bucks to see if thats the problem.

 

[RacerX-21]

Lots of good info here… let me add what I have learned.

As I see people become better racers and/or push their cars harder in terms of constant high RPM, the NSX starts to over heat. Then add higher performing engines and you have permanent cooling problems with heavy track use.

An oil cooler is defiantly a good idea.
20/50 oil is a must, but make sure you bring it up to temp.
I agree with insulating the front header near the oil pan.
The radiator needs to have shrouding from the front to the radiator or any resistance can cause turbulence in front of the radiator.
Run good coolant.
ARP studs.
Take the time to bleed the radiator system by the book… all of the bleed locations!
Target 200 degrees as max.


RTR had similar issues to solve, they ultimately ran with a hollowed out thermostat and welded shut the ~1” hole in the back of the housing… But they also ran a 3k+ and 7” thick worth of radiator that was sealed to vent out the largest hole you have ever seen in an NSX hood. And they still had high temps in 95+ degree days. They removed their electric fans (Like most race cars) to improve the airflow when the car is moving.

Other notes to help with your problem solving:

The OE NSX fan is especially restrictive.

In one case I had a blown head gasket that leak down tested perfectly, but when it got Race hot the combustion would blow air into the cooling system causing an air pocket and over heating. It would run forever without a problem if I kept the temps down. In addition the water stayed out of the cylinder and didn’t burn water.

High RPM causes heat exponentially. 5000 rpm to 6000 rpm might only be a 10 degree difference, but 6000 to 7000 might be 40 degrees, and 7000 to 8000 can increase 100 degrees (For example). In a race we lost coolant from a radiator that was damaged from the race before, the engine overheated and blew a head gasket. Some other cars had dropped out, so we decided to refill the coolant and go back out. After 3 laps of running hard and shifting above 8000 we overheated and came back in. We still needed 4 or 5 more laps to earn another position so we added water changed drivers and went out again. I needed more then 3 laps like last time so we collectively decided to short shift at 7000, after 5 laps we decided to stay out and go after the next drop out. The point is that at 7000 rpm we kept the car cool enough to finish the race and at 8000 rpm we could only get 3 laps.

At a point in my life I was a race engine builder who got some useful experience from our shop that built engines for many famous cars/drivers. In the Buick Grand National days we use to make some great power from the boosted V6, but the OE block only had 4 bolts per cylinder compared to most other HP engines with 5 or 6. We first went to ARP studs that helped but we still needed more so we went from 7/16” studs to ½” in the Iron block. If you needed even more power, you needed to go to the stage II block and heads with more bolts. Now going to ½” on the NSX wont likely help because aluminum wont likely handle any more torque, but the point is that 4 bolts per cylinder is not enough… especially with floating cylinders and lame gasket choices. A closed deck design will help eliminate cylinder shift that aids in the gasket letting go. This paragraph doesn’t solve your heating problem but may become useful in the future.

Many people have had gasket problems on the NSX. You have a few choices OE 3.0 (Worst), OE 3.2, Cometic steel shim, and Racers use copper with O-rings in the block or heads. But a better technology exists… Felpro and others build great gaskets for much higher performing engines, the difference is that they incorporate an O-ring into the gasket for combustion, and have “Print-a-seal” for the water. Its like having rubber o-rings around each water passage. Problem is that no company wants to tool up for the NSX engine. I finally found one that will and I will use them on my next engine.

Back to the heating-

Some race engines require additional hosing to rout more water to the heads.

I purchased one of those new vacuum radiator bleeders to 100% verify a good bleed. The dealers are starting to use them.

I have used the OE radiator, then a custom radiator that gave us some improvement, and then a Ron Davis radiator that had no gains over the previous. None of them solved the problem so I called multiple radiator builders to hear their advice. The common response was that since the larger radiator didn’t improve my temps, the radiator simply wasn’t getting enough air or possibly enough water flow.

During one of my over heating sessions I put a new normal thermostat back in and the over heating got worse. I changed back to the cut out one and cooling got better.

This said, I don’t think that having too much water flow is your problem; I think it’s just the opposite. Have you ever looked at the OE water pump? It’s pitifully small, especially for having to pump a system as long distance as in the NSX. Having too high of flow would only hurt you in slow moving conditions with minimal airflow. When moving high speed, the airflow should be so phenomenally high that it should have no problem cooling the volume from the 1-1/4” tubing below your car. Another note, the pump is driven by the back of the timing belt that wasn’t designed to drive anything. It’s possible that it might be slipping under a heavy load like high rpm.

My latest project is better ducting to the radiator and out the hood. Using the latest gaskets. Using the bleeding tool. Adding a 16” fan that flows better at high speeds. And most important- Adding an electric water pump to aid in the flow. I’m debating the elimination of the OE water pump to save 10-15 hp and possibly any problem causing affects it might have. But electric pumps aren’t that good, so it’s a flip of the coin, with major work needed to change it later.

Hope this helps, were all fighting the same problem but working together we can solve the problem quicker.

 

[docjohn]

Rob-As always nice to have your input, and keep up the r&d!In your talks with radiator makers,did you ever get the sense that bent fins on the radiator made a significant difference in cooling,I say this because mine are all bent up yet I have not had any cooling issues.

 

[Hrant]

Excellent review Rob, especially the differences in running at certain RPM intervals and temps. Short shifting seems to work for me as well.

John, what mix of radiator fluid/wetter are you using?

 

[docjohn]

Sad but true I'm using regular oem coolant,nothing fancy,no h2o wetter :redface: We have seen on the east coast temps quickly go up if folks run with the front plates on,but we don't seem to have as many cooling issues as you all on the left coast.

 

[RacerX-21]

Hi guys,

John,
No talk about bent fins but I have to think it makes some difference. Usually the application isn’t so marginal that you would ever notice a change.

Hrant,
I’m always trying to get the most of the car… It bugs me that I cant power shift and need to be nice to the trans… Short shifting all of the time would make me crazy.

You’re another candidate for a fix.

 

[NSX 3.0]

Rob-As always nice to have your input, and keep up the r&d!In your talks with radiator makers,did you ever get the sense that bent fins on the radiator made a significant difference in cooling,I say this because mine are all bent up yet I have not had any cooling issues.

Doc,
Mine were all bent shut also so I opted for a new OEM radiator hoping my overheating problems might end. I just got back from a track day and I still had some overheating issues. Funny thing is John V from AOB is still looking for a fix to this problem as there are quite a few NSX's that overheat at the track but not on the street. Maybe you guys can corner him and Mark B at NSXPO and get some answers.

 

[RP-Motorsports]

Well add me to the list.

I tracked my car for 2 years and the guage never went above 50%.

(ask anyone who has ever seen me run, and they will agree that it is hard to find anyone who pushes the NSX harder than I do)

Then all of a sudden one day at the gas station, I left it idle for 2 minutes and it went into the red!

A few weeks later I did a 2.0 mile road course in 90+ degrees and mine for the first time was creeping up, but only after back to back sessions at the end of the day. Steves went into the red, and Seans was creeping up a bit more than mine.

It was 100% fine for street driving, as long as no idling.

So yesterday I let it idle in the driveway and it went into the red, and blew steam out of the dump tube (Dali tank).

Enough was enough. For 2 years now I have been helping Steve diagnose is overheating issues. I have said to do just about everything mentioned in this thread but forgot the oil-cooler idea.

Ok back to mine.....

I checked for air (We did this a thousand times on Steves car, but never on mine. I had no air pressure at all!!!!!! Not even a drop of fluid came out of the front 2 spots!!!!! (skipped the rear at this time) I looked in the tank, and it was about 2/5th full. I got pissed and filled it to the top. I then started it up for 10 sec, and burped the front 2. I got some pressure but no fluid. I started it again for 10 sec, and now got air and fluid from the rubber one, but only air from the white one. I repeated about 2 more times and got all air out and good fluid pressure from all 4 spots. I looked at the tank, and it only dropped down to about 3/4. I then started it up and let it idle for 30 minutes. Wallah!!!!! Guage never moved from 1 tick below 50% and the fans went on/off/on/off/on/off etc etc. EXACTLY what it should do.

Conclusion. I think even a few "cups" low on coolant, makes the difference of running correct, and completely overheating, thus blowing the dump tube, adding air into the system from lower coolant levels, and higher engine temps, thus possible slight gasket leakage etc etc. This is just a downward spiral.

I am going to try to run a higher level of fluid, run the dump tube to a catch can that has the end of the hose submerged to reduce backwards air introduction, and run a higher pressure tank cap (22) and possibly a drilled thermostat, or absence of one. I am also going to add an oil cooler, and look into a higher volume oil pan.

I used to think that the thermostat was not allowing the hot fluid to circulate until it was too late, but now it looks as if the low volume (for some reason) was doing a combination of the following.
1) low volume= higher fluid temp
2) higher fluid temp= 16lb tank cap blowing steam
3) cap blowing steam= reduced volume even more and possibly introduced air
into the tank/system
4) air in system caused poor circulation, which raised temps even more, thus
blowing more steam, and possibly having the gaskets start to leak some air
into the fluid.

on and on..........

I am going to try the higher volume of coolant at the next event, followed immediately (if still an issue) the 22lb cap, low temp or no themostat, and fan on a toggle switch.

If that does not work, then I will try the distilled H20 and Redline Wetter.

Lastly a FAL fan (toggled) with a ducted shroud and hood.

I am also hooking the engine compartment fan to a toggle as well.

 

[RacerX-21]

You might have something with your theory about water level and the possibility of poor bleeding. Overheating then leads to permanent problems that will never be fixed before disassembly.

The water box that has the radiator cap looks like a typical automotive overflow but its not, it’s just the highest point to fill your system. An overflow catch-can with a water level above the bleed line would eliminate the introduction of additional air. Of course we already have air in the water box and it’s higher then the rest of the water system so it should never make it into the system… unless all the air wasn’t bled out and the water level has a chance to go lower, or a small head gasket leak slowly brings the level down (Or introduces the air).

Makes me think of another point- On some aftermarket water boxes like the BBSC box, might not be high enough to ensure no air gets into the system. If I recall correctly some water goes threw the intake up high near the throttle body?

Another thing that comes to mind, but I will need to look at it- When the heater core is removed and a bypass hose replaces it: A) it could trap air that wouldn’t be bled. B) It could act as a partial bypass for hot water not going threw the radiator (It no longer has a valve).

Two more notes-

Fans only flow enough air for no/low load conditions. A moving car will flow much more air then the fans can.

If you eliminate the functionality of the thermostat, the guts can be removed without destroying it. The parts are held together with an e-clip. The body has a rubber o-ring on it that acts as the housing gasket so its best to just disassemble it and put it back in.

The new bleeder I purchased seems to have a sound design, but I have not yet used it to verify its result. It also introduces some additional work, but not more then actually bleeding properly. First you must drain your entire system (If new, maybe you want to reuse it), then prepare a large container with enough radiator fluid mix as the car takes + extra so you have no chance of pulling air. You will also need a compressor to connect to the device. The device uses vacuum to bring its gauge up to a certain number after connected to your system. This also lets you see if you have any system leaks. It then draws the fluid into the system with no chance of air pockets. As I said I just got the tool and haven’t used it yet. This weekend should be a good time to try it. Eastwood sells it among others like Snap-on, but knowing what I wanted I went to E-bay (Not always available on E-bay).
Heres a picture-
http://www.eastwoodco.com/shopping/...&itemType=PRODUCT&RS=1&keyword=cooling+system

 

[nsxhk]

guys, any updates?

 

[CK_SB]

my $.02.

In my earlier days of tracking the NSX I too experienced oil related pressure problems. As I pushed the engine harder and harder for longer periods of time the oil pressure dropped as oil temps came up and the RPMs remained high. The oil pressure problem was solved after realizing the oil that I was running appears to have been foaming at high RPMs. A fellow racer and I changed the oil at the track to straight 50w (not my first choice, but perfect for this test) racing oil and this problem was solved.

As I pushed the car harder yet the stock cooling system, with water wetter and water only, could not keep up...water temps went into the red. I may have gotten lucky with my track car's cooling system so I thought I would share the set up. I ran Willow Springs last week and the car is running 7-8k rpm constantly and I am seeing water temps of 180F - 200F. California Speedway and Button Willow in the summer had the same temps.

Ron Davis Radiator (with a stone shield in front of it)
Water with Water Wetter (no Anti-Freeze)
2 FAL Cooling fans
Heater removed, (heater hose by-pass has bleeder in it)
O.E. Thermostat (fully assembled and functioning)
Cooling fans triggered by Thermoswitch and also by a cockpit mounted Thermoswitch By-Pass switch.

In this car the cooling fan By-Pass switch really makes a difference on overall water temp. If I allow the thermoswitch to activate the fans on the track the temps will go to 220+ F, but if I turn on the fan By-Pass switch as I roll onto the track, so the fans are running 100% of the time, I never see water temps climb beyond 200F, even in July. It appears that once the cooling system saturates with heat the upward cycle of heating begins and will not stop until you reduce the RPMs. By never allowing the temps to reach the capacity of the cooling system it seems to be able to maintain a reasonable temperature. I can't fully explain why my fan by-pass switch works so well to keep my temps down on the track, but I don't really care, it's clear that ram air is not enough and that with the aid of the fans running 100% of the time the cooling system is adequate. Slow speed corners at high RPMs and close proximity to other vehicles obviously reduces the ram air affect drastically and the slow response time of the thermoswitch may explain why a by-pass switch works so well.

Three other notes that are benefiting the cooling system and should be considered:

1- This car is running a 12 qt engine oil capacity with a large oil cooler. Oil temps are usually 215-218 F under hard track use.

2- This car is running a 4 qt transmission capacity with a moderately sized oil cooler.

3- This car is 500 pounds lighter then stock.

I don't know if this info. helps at all, but at least it will give you a bench mark for a track car that is cooling correctly.

Good Luck,

Chris

 

[RacerX-21]

Yes, but no test results yet I pushed my project back for someone elses deadlines.

1) Keep in mind that the higher the performance of the engine the higher rate it will develop heat.
2) When bypassing your heater core by running a hose from the heater line to the bleeder tube, your essentially allowing an estimated 25% of the hot water to bypass the radiator.
3) I added perfect ducting from the nose to the radiator.
4) I opened the area of the nose for greater volume.
5) I also build sealed ducting to vent from the radiator out the hood.
6) And last I added a secondary 37 gpm electric water pump to aid the small OE unit

I may need to play with a lip on the leading edge of the hood if I run into any flow problems exiting the radiator. I will use streamers or a smoke bomb to check for turbulence.

If this works I plan to build my next engine without an OE water pump impeller to save a few HP. Some of you may have noticed a shiny glaze on the outside of your timing belt, this may be an indication of water pump slippage and heat is defiantly not good for belt life.

The only thing left if this doesn’t work is to re-route the water in the heads. This will be the next step for me if what I’ve done hasn’t solved this issue.

 

[RacerX-21]

New Info-

I recently rebuilt a stock 3.0 with Comptech cams, adjustable cam gears for degreed and changed centerlines, 3.2 head gaskets, headers, Intake manifold mod, and an AEM for tuning. It’s no super hot turbo car, but it does have 10.7:1 compression with the gaskets and makes about 300-rear wheel. This dyno run had the coolest water temps of any I have ever encountered, including stock rebuilds. The car has a larger radiator (Not quite Ron Davis size), but in the past I have seen little temperature reduction with larger radiators at a dyno. Not enough air flow.

Changes that may have contributed to the good temps-

Mugen low temp thermostat.

The heater core water routing is now plugged at the engine and the front hose, rather then using a bypass hose to jump from the inlet hose over to the outlet hose by the battery. The heater core has a valve to stop flow when interior heat isn’t needed.

When installing a Comptech oil filter adaptor for an oil cooler or an Accusump, we usually plugged the OE oil cooler lines… But, I was thinking that the OE flow path might be needed so I ran hose for the original path, only bypassing the OE cooler.

All of the above are low cost modifications and seem plausible for temp reduction… but!

My gut says that the most likely solution was my new vacuum coolant tool. This tool is one I read about that helps the widespread import problem of getting all the air out of your coolant system, especially rear engines. I first used it on this car and now I will use it on every coolant system fill.

Coolant tool-
It’s a simple gun with a rubber cone, a gauge, a trigger, a valve, and a long clear hose. You plug your compressor line into it, and run the clear hose to a clean 5-gallon bucket with mixed antifreeze. The cars coolant system needs to be drained first. Then place the universal rubber cone over the coolant filler opening (The one your radiator cap was on).
The first thing it does is draw a vacuum in your coolant system, keep the trigger pulled for a minute or so until the gauge reads it’s highest vacuum. (The trigger has a latch so you don’t have to hold it). The vacuum actually collapses many of your hoses… this is normal. Release the trigger and the air line, then let it sit for 2 minutes to see if you have any system leaks… sure enough I did, on one of the large radiator hoses in the front and one small hose that runs from the engine to the filler bottle. I replaced the clamps with high quality stainless steel clamps (The ones with serration gears are stronger then the ones with open cut gears). If you have the time and budget, it’s not a bad idea to replace all of the OE clamps, as they defiantly don’t clamp as strong. Now that the system holds pressure and wont likely leak or introduce air. Reconnect the air line and draw vacuum again, then slightly open the valve to draw some coolant up the clear hose to purge any air in that hose. Close the valve, draw max vacuum, disconnect the air line, and open the valve. The vacuum in your coolant system draws the antifreeze into it, eliminating any chance of introducing air or having air trapped somewhere obscure like the water pump. I add 10% more coolant to the 5 gallon bucket so I have no chance of sucking air.

Even if you were to purge all of the OE bleeders, it would be difficult to get all of the air out, especially in aftermarket radiators that don’t have bleeders at the highest point. Any air that made it to the water pump would cause cavitation and would reduce your water flow.

Soon I can test these methods on a much higher performance engine, and I have a few more ideas just in case.

 

[nsxhk]

New Info-

I recently rebuilt a stock 3.0 with Comptech cams, adjustable cam gears for degreed and changed centerlines, 3.2 head gaskets, headers, Intake manifold mod, and an AEM for tuning. It’s no super hot turbo car, but it does have 10.7:1 compression with the gaskets and makes about 300-rear wheel.

Wow.... Great news!! That sounds like a do-able setup for 300rwhp! How much did that cost?

3.2 head gasket on a 3.0? I heard the 3.2 head gasket is a better make than the 3.0 but do you need to do any modification to the gasket or head to make it fit?

Thnx.

Henry.