Still overheating

[mikeh]

NSX-Racer,

I'm not trying to rain on your parade or give you a hard time or anything, but it sounds like your techie is talking you into spending a buncha money that 'might' fix the problem instead of actually figuring out what the problem is. Why don't you have the original radiator tested, and if it's ok, reinstall it?

Also, I dont recall, but is your engine and ems stock? (besides exhaust/headers/intake)

You shouldn't be dropping to around 0 psi when vtec engages, even with the crappy ass oem oil pressure sensor. To me, it sounds like your heating up because of a lack of oil pressure. I'd be surprised if you didn't have any issues with your cylinder walls if you've been running like this repeatedly.

I take it you don't have an accusump?

I really don't mean to offend you by saying this, but if your current tech can't figure out why it's over heating before you dump more money into aftermarket parts, you should take it somewhere else and see if they can figure it out. (i don't mean ditch the guy forever, just let someone else take a peak and try to figure it out. 4 eyes are better than two)

Good luck!

-mike

 

[DutchBlackNsx]

You shouldn't be dropping to around 0 psi when vtec engages, even with the crappy ass oem oil pressure sensor. To me, it sounds like your heating up because of a lack of oil pressure. I'd be surprised if you didn't have any issues with your cylinder walls if you've been running like this repeatedly.

Do a search on this matter, and you find lots of info on it.

In short, very common thing on the NSX.


I do agree on your other points though.

Mich

 

[Larry Bastanza]

Wolfgang,

If you suspect two high a flow rate in the radiator just pinch one of the lines slightly (exit line, upper radiator hose, would be best). Cheap and easy.

Also does the car get better if the heater is on??

HTH,
LarryB

 

[NSX-Racer]

Thanks for your input, guys - nobody can rain on my parade because I'm no techie myself :wink:
Larry, the heater is disconnected so no chance to test this. I don't think that the flow rate alone is the problem with the radiator - it's the different flow pattern or directions which wasn't designed well (other and worse than stock). That's at least what the techie said - I've not much clue myself.

Mike, the engine and ECU are stock, I have no accusump, I had no overheating issue in former times with the stock radiator as long as it was still okay. But after some years of tracking nearly all the fins where bent by stones etc. (had no sufficient guard) - overheating started and so it was replaced. No sense to mount it in again. I don't think the oil pressure issue has any bad effects - I see that gauge now for more than 6 years and I'm pretty sure my engine would be already dead after about 130,000 kilometers (I guess more than 20,000 km of that on the track) if that would be a problem.

I have not paid a single cent yet for all the latest work and parts and I will only pay for things that will work - the rest is a R&D issue for my techie. OTOH there is no single NSX expert nearby - all the left Honda dealers in the region haven't even seen a NSX in their life at their shop.

 

[Larry Bastanza]

ALWAYS remember the coolant MUST flow in the bottom and out the top. I hope this is the case with the radiator you have. It will not flow otherwise(air pocket will result). I have much experience with oil coolers in this regard, after more then one destroyed Porsche race engine.

If you review the NSX on-line service manual, page 5-14 you can confirm this is the design of the NSX coolant flow also.

HTH,
LarryB

 

[SCS2k]

Warped heads? Cracked block?

 

[NSXTech]

Code 22 makes sence to me, but is scary. When the computer 'sees' v-tech it is very criical of the amount of oil pressure the sensors on top of the spool valves report. It sounds like your car is getting very hot and your oil pressure is dropping dangrously low. Do you have a reliable o/p guage, or is it stock?
What grade oil are you running?

I agree with the last few posts about upgrading other parts / sytems before you find the problem. You will only mask it oherwise In adition to the leak down test, I would do a combustion gas test to see if CO is present in the coolant. As Jim mentioned, they may have missed a crack or bad surface.



MB

 

[NSX-Racer]

In adition to the leak down test, I would do a combustion gas test to see if CO is present in the coolant. As Jim mentioned, they may have missed a crack or bad surface.

As I already wrote the CO was tested two times - before the changing of the head gaskets there was CO in the coolant, afterwards none - I also don't think therefor that I have a serious block or head problem but I will let my techie check that once again.

 

[hlweyl]

I know your tech said a leak down test wasn't necessary but as I suggested before, I don't think having one would hurt at this point. Sometimes it can point you in the right direction.

 

[Eddy]

On a side note... I have a coolant temp gauge installed. After 7 laps on track, the coolant reach 103C. Is that high? I was too busy looking at the aftermarket coolant temp gauge and never got a chance to look at the oem temp gauge so I don't know if it's in the red zone or not.


Henry.

My NSX does the same on the track.. It would hover 1-2 lines below red if you keep the rev between 6000-8000.. The other day when mapping the fuel map for my M800 on the dyno, a constant speed run of 8000 rpm (from part to full throttle) for about 60 seconds shoot the temp from 93deg to 100deg in no time.. It's nothing to be alarmed about though.. I've seen coolant temp go up to the range of 110-115 without blowing the pressure cap.

But I have no problem with the engine on the highway.. 93-94deg consistently and goes up to 95-96 when going up a steep hill..

Personally, I think the C30A engine generates quite a bit of heat and the stock radiator doesn't quite do the job at full load.

Eddy

 

[NSX-Racer]

I've seen coolant temp go up to the range of 110-115 without blowing the pressure cap.

The NSX ECU cuts off maximum rpm at overheating and may even go into emergency mode long before the pressure cap blows - that's at least my experience.

 

[DutchBlackNsx]

The NSX ECU cuts off maximum rpm at overheating and may even go into emergency mode long before the pressure cap blows - that's at least my experience.

My NSX (1992) had a few severe overheats, and never went into limp mode.

 

[NSX-Racer]

Didn't it even cutoff the maximum rpm at 7000 at this cases? Would make me wonder if they have changed something in the ECU regarding that behaviour between your model year and mine ('98).

 

[SCS2k]

I know this may sound stupid and it may have already been asked but is there anything in front of the radiator that may be impeding air flow? Some type of stone shield or something?

 

[NSX-Racer]

It is just a net of thin metal strings - about the same you use as a fence for a small rabbit at home :biggrin: - not much of a resistance for the air.

 

[NSX-Racer]

Sorry that it seems I beat this thing to death but I want to add some new infos after a call from Honda Germany and another talk with my techie.

Honda technical service man says: Possible reasons for overheating a NSX on the track are:

Stock radiator isn't capable of enough cooling for heavy track use - that's why they changed also to an aftermarket radiator at the 24 hours Nuerburgring NSX-R (just mentioned in another thread) which was bigger and thicker. They even altered some of the parts in the front compartment to give the radiator more room. My techie agrees - new radiator will be mounted.

Honda techie says: If the oil temperature exceeds 140 C the ECU reduces max rpm and even go into limp mode to avoid Vtec and other engine problems. My techie agrees and says his measurements show oil temps in the region of 145 C in my engine. That's why we add an oil cooler.

Honda techie says: Maybe the engine is running lean because the Lambda sensor gives false measurements to the ECU (my cats are removed). Lean running leads to more heat. My techie says: Rubbish - normal cats work only up to 60% of full load, afterwards (and I'm running always full load at the track) the ECU always sets the Lambda 1 relation (I guess it's 7:1) no matter which sensor measurements. His conclusion: Engine is not running lean at full load.

Honda techie says: Leak down or compression tests are not necessary in my case - if I have no combustion in the coolant (I have not after changing the head gaskets), no coolant leaks, no power loss, no oil leaks etc. I would have no engine problem like cracked blocks or blown gaskets. Serious engine problems would be remarkable very fast under heavy track use. My techie agrees.

Honda techie suggests installing an oil temp gauge - we will do that together with the installing of an oil cooler. After all this modifying the car will be brought on a dyno - not only to test the power but also if it overheats under full load with not much streaming air (At the dyno they usualy only have fans in front of the car to give about 90 km/h airstream).

 

[Hrant]

Good step by step feedback. I think you might be amongst the first to crack this case .... :biggrin:

Where are you installing the oil temp gauge?

 

[NSX-Racer]

A good place would be the black plate where formerly the radio and the ashtray were installed, I guess.
And of course I hope to be the first who cracks the case :biggrin: (and when I get the big invoice I can't even have the profit of it because my season would be over before the next event due to the lack of money...)

 

[NSX-Racer]

Another update: We found a cheaper possibility to check if the efforts are worthy. Instead of driving on a track we just put the car on a dyno with only a weak airfan from the front and then do some full load tests. Result: 1st try had to be abandoned after about 4 times of accelerating - engine did get hot although we mounted another radiator and an additional oil cooler. Try was stopped before the water and oil temp gauges went into the red zone. So no power data at this time.

Inspection showed that the oil cooler thermostate opened too late (at about 96 C). Thermostate for the water flow is removed so we have a constant flow and that should not lead to a problem. Everything else seemed to be fine - water flow from pump, ignition timing, gaskets. Next dyno try will be on tuesday with a different oil cooler thermostate and a stronger fan behind the radiator.

OTOH I'm still not convinced that a stock engine should get too hot so quickly even under this conditions - but I don't know where to search further. Any thoughts besides these already mentioned here?

 

[Hrant]

An off the wall question. What brand and concentration of radiator fluid are you using?

Al Terpak, who too was having overheating problems, changed his radiator fluid with an off the shelf brand from an auto parts store (not the Honda brand) and at the last track event where the ambient temp as in the 90F and he was pushing hard, he did not have the problem! I still had overheating after 4-5 laps.

Since here in NorCal we don't see the freezing weathers of the NE or MW, I am thinking of going 70% water and 30% concentrate mix, and if need be adding a bottle of wetter again.

 

[whrdnsx]

You mentioned you removed the Water thermostat for increased flow, however in some cases that can cause some overheating as the water flow is too fast at high RPM to be cooled properly by the radiator. I had this problem on my Production type race car I ended up making a restrictor plate to go in place of the Thermostat. About a 13mm hole from memory & this cured my problem.

A leakdown & cooling system pressure check with the engine preheated is the first step.

 

[NSX-Racer]

Good points, guys, thanks. But a dumb question: Doesn't a reduction of the diameter increase the flow speed?

 

[Edgemts]

Good points, guys, thanks. But a dumb question: Doesn't a reduction of the diameter increase the flow speed?

Hate to tell you this but my first guess is that if you put the stock thermostat back in or put the mugen one in your problem may go away.
I made a similiar mistake, one of the tricks we always did on our race motors was to cut out the thermostat mechanism so it was open, but the key there was not to remove the entire thing because the water would flow too fast through the radiator and would not cool. I cut my stock thermo but it didnt work on the NSX at track speeds, tuning it/ driving on the street it would never even get up to operating temps, but as soon as I went to the track the gauge was pegged after 3 laps.
The NSX seems to need a thermostat, if you look at it it actually has 2 different plungers. I have not yet had a chance to r+d the modifications needed so that I can remove the thermostat, soon. :smile:
I will also say that I also have a head gasket problem(blown- pressurizing the coolant system) but I am fairly confident that once I fix the engine, I will no longer have cooling issues.

 

[NSX-Racer]

Thanks edgemts, but over the whole time the problem occured the thermostat was in (and it's not broken). I just removed it the last time to see what it may change - obviously nothing. But okay, I may mount it again.

 

[Edgemts]

Thanks edgemts, but over the whole time the problem occured the thermostat was in (and it's not broken). I just removed it the last time to see what it may change - obviously nothing. But okay, I may mount it again.

I was going off your first post in MArch that said you had removed it, and that its been out since the new gskts. ???
Next week I am goign to work on some different things to contol water temp a little better. I will let you know what I come up with.