Heat in the tunnel pt. 2

[bngl3rt]

The story so far...

Driving home from work one Friday afternoon, roof off, taking the long, twisty way. Notice for the first time heat coming from the shift boot and the gap in the rubber gasket behind the parking brake. Very strange. Concerned, I pull over, pop the hood, and wait for the fan to kick on (left the car running). It does, but in short order the car overheats (temp gauge spikes) so I shut off the car, let it cool on the side of the road with the engine hatch open for half an hour or so, then babied it home with the heater on and the windows down.

Turned out that I had been losing coolant on account of a misplaced hose clamp in the tunnel, and I guess that day I finally lost enough to overheat (and blow the head gasket...). This also explains the heat coming from the tunnel, as I found coolant stains around the end of the hose, so I assume hot coolant (steam) was pouring out of there while I was driving.

So the HG was replaced and the hose clamp moved back into place. But, I was still feeling heat coming from the tunnel under hard driving. What the heck??

Well, turns out that when the engine was dropped to replace the HG, the small rubber gasket that the shift cable runs through into the passenger cabin was torn (yes, in case you're keeping score, all issue so far were caused by careless workmanship...) and that explains the heat from the tunnel leaking into the cabin.

Of course, there's no way to order just that gasket - it comes with the change cable assembly ($600+) and the labor to drop everything out and replace that cable is substantial. So, as a stopgap, my (new, careful) tech told me he filled in the tears in the gasket with some kind of flexible foam that should take care of most of the heat.

Unfortunately, it didn't. So, what should I do? I know it's not a sign of anything being wrong with the car - coolant levels and temps are stable under all kinds of driving now. It's just distracting and annoying.

I can either spend the likely four figures to get a new shift cable assembly installed (when all I really need is that tiny rubber gasket - might even be doable from the cabin side), or maybe I can put some kind of other heat shielding underneath my center console?

 

[nsxnut]

I would think some Silicon RTV should take care of it.

 

[E-Nough Logic]

Depending on how this is installed you may not be able to physically replace the seal without the cables which is why it is sold with them. RTV should do the trick here like said above.

 

[bngl3rt]

Hmmm... I'm also in the middle of debugging an oil leak that I suspect is in the timing cover area (replace oil pan + gasket twice and still leaking).

Not sure if the procedure for getting at the timing cover area would yield access to the transmission such that this piece could be replaced? I'm all about not duplicating work

 

[Thunder]

Often leaks oil on Honda NSX has a bad wound gaskets for valve covers, especially the rear cover, oil arrives at the same place by gravity, on the left side of the oil pan , not ask how I know ... attached for your missing, maybe you could make one yourself with silicone rubber or liquid ? (heat resistant)

 

[bngl3rt]

Hmm... My leak is definitely on the passenger side where the timing cover is. Thanks for your insights though.

 

[bngl3rt]

Was reading the service manual and wondering if I can get in from the passenger cabin without having to put the car up to add the RTV...

 

[Larry Bastanza]

I have to say, I am really struggling with the thought that this tear is bringing heat into the car, maybe taking it out. That is a water seal, and if the car is moving forward, there is little chance air is moving in the opposite direction of the car and putting heated air from the engine bay into the interior. Did you do a pressure test on the entire coolant system and does it hold pressure? Could be wrong, but it sounds like something else is causing this, not that boot. Like a water hose still leaking in the tunnel.

Since you made the point about poor workmanship, I am thinking there is a score in the aluminium pipe that one of the three hoses are connected to, and it is a permanent leak. BTW, all six hose ends on the three hoses in the tunnel have aluminum pipes that can easily get scored if imporperly handled during a hose service.

HTH,
LarryB

 

[bngl3rt]

LarryB, thanks for your insight. I will ask for another pressure test. I assume (perhaps incorrectly!) that any head gasket replacement is followed by a pressure test...

 

[Coconut]

This might be a step backwards but can you prove that the tear was caused by whoever dropped the engine? If so then they should be responsible in getting whatever parts are needed and labor involved in correcting their mistake?

 

[bngl3rt]

This might be a step backwards but can you prove that the tear was caused by whoever dropped the engine? If so then they should be responsible in getting whatever parts are needed and labor involved in correcting their mistake?

From what LarryB said it sounds like the tear was cause by improper hose replacement, which also left the hose clamp out of place. In this case, that would involve returning to Hilltop which is something I'd really rather not do.

It is a tough situation to be in-deal with a shop I hate because they broke it, or pay another shop out of pocket to fix it?

 

[Coconut]

If the cost is significant (and it sure sounds like it is) then why not have Hilltop fix it? You shouldn't need to pay out of pocket for their mistake.

Another issue is if you feel they are incompetent in fixing it. From your past experience with them I would be hesitant as well. Thing is Don has been working with NSX's for so long and I'm sure he KNOWS how to do it right but as of recent he's been sloppy and and rude. Not sure if its due to a personal reason or he's just getting tired of it all. Either way he is RESPONSIBLE for fixing it right and as far as I'm concerned his reputation is on the line.

 

[Larry Bastanza]

From what LarryB said it sounds like the tear was cause by improper hose replacement, which also left the hose clamp out of place. In this case, that would involve returning to Hilltop which is something I'd really rather not do.

It is a tough situation to be in-deal with a shop I hate because they broke it, or pay another shop out of pocket to fix it?

Please remember guys I am speculating based on what I read. I have known Don for a lot of years, and I would be shocked IF this would be poor workmanship from Don.

Regards,
LarryB

 

[bngl3rt]

Please remember guys I am speculating based on what I read. I have known Don for a lot of years, and I would be shocked IF this would be poor workmanship from Don.

Regards,
LarryB

LarryB, I really appreciate your insights. I am not looking to place blame - just trying to diagnose and fix my problem. Hilltop replaced my hoses a few months ago, not sure if it was Don or one of his employees. However, I didn't start feeling the heat right away after the hose job.

A few days before I started feeling the heat in the tunnel some unrelated work was being done on my car to diagnose an electrical problem (turned out to be a frayed wire pinched and shorting on the intake manifold) but they were working from the top of the engine bay so no reason for them to have been under the car or had the tunnel cover off. Exactly how and when the hose clamp got moved out of place is a mystery.

Since the heat is coming from the back of the tunnel, I'm guessing 19510-PR7-A00 will need to be replaced.

 

[bngl3rt]

Here's what's weird: the coolant level isn't changing. I check it before every drive, and after the car has cooled off from driving. Even over weeks it's steady (whereas before it was losing 1/2" to 1" a day out of the tank).

Very mysterious. I'm still confused...

I might just replace 19510-PR7-A00 for the hell of it at some point to see if the problem goes away (along with going to all-new SoS silicon hoses and clamps) but that is probably going to get expensive.

 

[bngl3rt]

Well, the car is back at the shop that diagnosed its last mysterious issue... fingers crossed they can figure this one out as well.

 

[shawn110975]

get the OEM hoses and dont look back. buy SOS OEM hose kit
use the ones you need and sell the remained hoses on prime
someone can use them get part of your money back.

 

[bngl3rt]

get the OEM hoses and dont look back. buy SOS OEM hose kit
use the ones you need and sell the remained hoses on prime
someone can use them get part of your money back.

Unfortunately, I just had the hoses replaced within the last few months so I doubt it's those. LarryB was saying it might be the pipes (as in the aluminum parts), which are much more expensive and difficult to replace.

 

[bngl3rt]

Well, the cooling system holds pressure. No leaks.

Might replace the radiator with a Koyo because I only measure about 5 celsius difference between the two radiator hoses after a long drive.

Also, I have aftermarket carpet which apparently doesn't have the same insulation as the OEM carpet. Though, the top of the tunnel doesn't have any carpet on it anyway....

Very stumped here, folks. Two NSX techs were unable to reproduce or diagnose the issue.

 

[bngl3rt]

Okay, here are my two newest theories:

The car sat for about two years before I bought it during which time apparently calcium deposits can form in the radiator. The coolant has since been changed so these should be starting to wear away with driving and use, however....

Either a) Coolant flow through the radiator is severely restricted, and as such the overall efficacy of the cooling system is reduced. Therefore, even though the pipes/hoses in the tunnel are not leaking, they are actually just radiating heat. This will likely wear them down and cause a hose clamp to pop in the long run.

or b) Because the cooling system can't work fast enough, the coolant is getting much hotter than it should, which means the air passing over the radiator is getting much hotter than it should, and hot air from the hood compartment is getting pushed into the tunnel simply by the force of air moving from the car moving.

Any thoughts on either of these?

 

[9doors]

Well, the cooling system holds pressure. No leaks.

Might replace the radiator with a Koyo because I only measure about 5 celsius difference between the two radiator hoses after a long drive.

Also, I have aftermarket carpet which apparently doesn't have the same insulation as the OEM carpet. Though, the top of the tunnel doesn't have any carpet on it anyway....

Very stumped here, folks. Two NSX techs were unable to reproduce or diagnose the issue.

I will have a Koyo radiator for sale in the next month or so. Only 500 miles on it. PM me if you have any interest.

Another thought is there is a possibility that your head bolts have begun to strip the block and you need to have the block time serted. This is what the final result of my similar temperature issues has become...:frown:

 

[bngl3rt]

Another thought is there is a possibility that your head bolts have begun to strip the block and you need to have the block time serted. This is what the final result of my similar temperature issues has become...:frown:

Hmmm... When my HG blew, they installed aftermarket ARP head studs so considering the rest of my car is stock (no sc or turbo), would that mitigate or accelerate the stripping?

 

[9doors]

Hmmm... When my HG blew, they installed aftermarket ARP head studs so considering the rest of my car is stock (no sc or turbo), would that mitigate or accelerate the stripping?

*If* the problem is actually with the block, the ARP might have accelerated the process. Just a thought, since I'm very far from being an expert on this topic.

 

[Old Guy]

In your original post, you noted that the temperature gauge spiked prior to you shutting the engine off. Since replacing the head gasket, fixing the coolant connection and eventually doing the pressure test, you didn't make any mention of whether the temperature gauge has indicated that the engine is running hot. If the temperature gauge is indicating normal operating temperature, I would jump to the default conclusion that the cooling system is working ( don't get hung up about the apparent lack of temperature drop across the radiator).

The preceeding comment is based upon the assumption that the thermostat and the temp sensor are working. Quite often, when you have a significant loss of coolant, the thermostat, which sits in a high spot in the coolant loop, will get 'cooked' and may fail open, closed or rarely 'somewhere else'. Open or closed are usually obvious, somewhere else isn't. Since the head gaskets were replaced because of the overheating, I would hope that the thermostat was either tested or replaced as part of that maintenance. The temp sensor sits in the same housing as the thermostat and as such would also be one of the first things to be overheated following loss of coolant (perversely, because it sits so high in the engine, once the coolant drops below the sensor it may cease to register a high temperature). I have never had one fail or go out of tolerance because of an overheating condition; however, I have also never experienced overheating / loss of coolant on a Honda/Acura, so I have no direct experience with what happens to Honda sensors.

Short answer - if the temp gauge and thermostat are working and you are not registering abnormal engine operating temperatures, the cooling system is probably not your issue. I also suggest that the head studs are a red herring.

Now for some guessing as to where your heat may be coming from. In your post, you described heat coming from the tunnel. However, I was never quite clear as to whether it was hot air exiting from the gaps around the shifter / hand brake or whether it was just that the shift boot and other parts felt abnormally hot. In subsequent replys there was discussion of the torn rubber boot on the shift cables and (presumably air) leakage past this boot, so I am going to assume that we are talking about hot air exiting from the gaps. That said, if the ducts that connect the heater-evaporator unit to the outlets in the dash have become separated from the unit, it might be possible that you are leaking hot air from the heater-evaporator into the center console area which is then exiting in the gap around the shifter and hand brake. The easiest way to test this may be with the engine on and up to operating temperature, heater on at max fan speed and the car parked. If hot air is exiting from these gaps then I bet that you have some air leakage from the heater-evaporator into the center console area. If you turn the fan off and the leakage stops, I think you have your solution. If that isn't the problem, then you can print out this reply, wad it up and throw it in the garbage!

 

[bngl3rt]

Now for some guessing as to where your heat may be coming from. In your post, you described heat coming from the tunnel. However, I was never quite clear as to whether it was hot air exiting from the gaps around the shifter / hand brake or whether it was just that the shift boot and other parts felt abnormally hot. In subsequent replys there was discussion of the torn rubber boot on the shift cables and (presumably air) leakage past this boot, so I am going to assume that we are talking about hot air exiting from the gaps. That said, if the ducts that connect the heater-evaporator unit to the outlets in the dash have become separated from the unit, it might be possible that you are leaking hot air from the heater-evaporator into the center console area which is then exiting in the gap around the shifter and hand brake. The easiest way to test this may be with the engine on and up to operating temperature, heater on at max fan speed and the car parked. If hot air is exiting from these gaps then I bet that you have some air leakage from the heater-evaporator into the center console area. If you turn the fan off and the leakage stops, I think you have your solution. If that isn't the problem, then you can print out this reply, wad it up and throw it in the garbage!

Thank you for your insight. The thermostat was replaced during the HG job so hopefully if it was "cooked" it isn't anymore... The temp gauge has also read normal temps since the HG job.

It doesn't really feel like there's any force pushing the hot air out of the gap around the e-brake... mostly they are just abnormally hot to the touch.

I will try what you've suggested! Since the cooling system really does seem to be working okay, I have been wondering if it could be related to the heater. Another tech suggested a leak or other fault in the air mix motor, which also makes sense. I did bleed the heater core and verified that it is not mixing any air into the coolant that's running through it, but it could be related to the problem in some other way.