Coolant Gauge Got Hot Momentarily...

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Jun 26, 2021
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Hi Gang,

Yesterday while I was driving my coolant gauge went up (almost all the way) momentarily, the warning message on the center of my dash came on (pull over when safer, engine is hot). By the time I was done reading the message the gauge had gone back down to normal and the message was gone. This all happened in about 15 seconds.

Anybody ever experience this?

Thanks
 
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Hi Gang,

Yesterday while I was driving my coolant gauge went up (almost all the way) momentarily, the warning message on the center of my dash came on (pull over when safer, engine is hot). By the time I was done reading the message the gauge had gone back down to normal and the message was gone. This all happened in about 15 seconds.

Anybody ever experience this?

Thanks


Was this after really hard driving? Or just random? If the latter, you might just have an air bubble in your system that worked its way past the temp sensor. I'd take it to Acura, describe the issue and have them bleed the coolant system just to be sure. On the NA1/2, this is often the sign of a blown head gasket...
 
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Was this after really hard driving? Or just random? If the latter, you might just have an air bubble in your system that worked its way past the temp sensor. I'd take it to Acura, describe the issue and have them bleed the coolant system just to be sure. On the NA1/2, this is often the sign of a blown head gasket...

dam...just realized i disconnected the expansion tank to connect the JB4 Science Of Speed Tune, so I would assume I got air in the system...what cap would I bleed it from? The one in the front or the cap on the actual expansion tank?
 
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As I recall our coolant system has a lot of places to vent in the process of removing air from the system. You might want to converse with a NSX Tech assuming they will chat or pay the subscription fee at Honda and look over the process of flushing the coolant. That air bubble has probably moved around since you last let it in. Good luck
 
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Considering how important coolant is and how it might need attention while on the road and not near a dealer, it would be nice if the basic information were given to all owners. My first mid-engine car (1985 Toyota MR2) had coolant bleeding instructions in the owner's manual that came with the car.
 
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dam...just realized i disconnected the expansion tank to connect the JB4 Science Of Speed Tune, so I would assume I got air in the system...what cap would I bleed it from? The one in the front or the cap on the actual expansion tank?

As I recall our coolant system has a lot of places to vent in the process of removing air from the system. You might want to converse with a NSX Tech assuming they will chat or pay the subscription fee at Honda and look over the process of flushing the coolant. That air bubble has probably moved around since you last let it in. Good luck

I'd take it to Acura and have them bleed/burp the system properly. You don't want to screw around with air bubbles on an aluminum block with aluminum heads, especially in a boosted engine. Probably a few hundred bucks, but it will save you the worry of popping a head gasket or warping your expensive block/heads.
 
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sooo i dropped it off at acura, they had no idea how to burp the system, only one NSX authorized mechanic, he let the car idle and verified it got hot...he also said it showed the car did get hot on the computer as well (so it does appear the computer logged it). He also said if it did truly overheat the check engine light would have turned on and the car would have turned off...so i'm not sure what to think of that or if it's even true. dealer seemed just fine that I had a JB4 on the car and asked me to flash it back to stock tune...so I did feel good about that part. They are clearly interested in making the money off the warranty from acura I would assume..

I then asked them how long it would take to burp the system and they instead wanted to do a coolant flush...I said fine, just want this done. Service advisor then told me he didnt have the NSX coolant in stock and would need a day or two to get it...then they told me not to drive the car until thats fixed...then they told me no loaners as they are all out...

boy oh boy...home now waiting to hear back but I did not feel good about leaving my car there with the NSX mechanic. He made it clear he has never flushed or burped the system on the NSX...

thoughts???
 
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The good news is that the tech was upfront about not knowing the bleeding procedure so he will probably be smart enough to contact field support about what to do next rather than just making it up as he goes and hoping for the best. My guess is that you will be just fine but modifying a car under warranty is playing with fire because no one at AHM wants to pay for problems created by parts and labor performed outside their franchised dealership system. Why would they? They think their engineering department is better at creating reliable parts than an aftermarket hobby shop, and, if nothing else, making more horsepower alone can create all sorts of unintended consequences.
 
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Probably not anything crazy for coolant. When I had my 360C I flushed the coolant a few times. Similar layout and it’s involved but not very hard. Had to burp each front radiator and the rear did itself with the expansion tank. On the Fcar lots of debate on the right coolant but it’s readily available.

When the NSX dealer flushed my brake fluid they claimed it was something special and it took a couple days to get. Sure I had a perfectly good substitute on my garage shelf. So it goes.

The hardest part is leaving your car there - sure it will be fine and you’ll be back to driving soon.
 
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Not to worry the earlier cars are also complex in getting rid of air. Keep in mind that the radiator is up front and then works it’s way back to the engine. So there is a sequence in how you go about getting the air out. As for fluid, it is probably one that is special for the aluminum and meets other criteria as well. I considered having my system flushed but decided against it as it is still relatively new. You can probably go either way, that is bleed the current system or flush the system. As for the NSX tech not jumping on the car right away, be happy that they care so much about doing the right thing versus just going for it. My locale dealer lost his NSX tech to retirement and will not touch my car for fear of going against Acura and their requirements. It might annoy me but in the end I appreciate their following the rules. This is after all one of my loves.
 
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just got a text that the tech contacted acura-tech line. waiting to hear back from them...what a process! lol
 
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sooo i dropped it off at acura, they had no idea how to burp the system, only one NSX authorized mechanic, he let the car idle and verified it got hot...he also said it showed the car did get hot on the computer as well (so it does appear the computer logged it). He also said if it did truly overheat the check engine light would have turned on and the car would have turned off...so i'm not sure what to think of that or if it's even true. dealer seemed just fine that I had a JB4 on the car and asked me to flash it back to stock tune...so I did feel good about that part. They are clearly interested in making the money off the warranty from acura I would assume..

I then asked them how long it would take to burp the system and they instead wanted to do a coolant flush...I said fine, just want this done. Service advisor then told me he didnt have the NSX coolant in stock and would need a day or two to get it...then they told me not to drive the car until thats fixed...then they told me no loaners as they are all out...

boy oh boy...home now waiting to hear back but I did not feel good about leaving my car there with the NSX mechanic. He made it clear he has never flushed or burped the system on the NSX...

thoughts???

That wouldn't give me the warm and fuzzies either. That said, even on the Gen1 cars, while more complex than the average car, the coolant flush and bleed procedure isn't that bad. You just follow the steps in the manual. I'm sure the NC1 manual has a similar procedure that the tech can follow. My concern (and apparently Acura's) is that the bubble is still in the system somewhere. If you get a steam bubble in the wrong spot....boom.
 
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yep, it's very odd too because the car stays right under the halfway mark (coolant gauge) when driving and then once i stop it creeps up to 3/4 then goes back down...so the bubble is moving around...I would think. Does anyone think that few seconds the gauge got hot could have caused any damage?
 
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yep, it's very odd too because the car stays right under the halfway mark (coolant gauge) when driving and then once i stop it creeps up to 3/4 then goes back down...so the bubble is moving around...I would think. Does anyone think that few seconds the gauge got hot could have caused any damage?

On the 3.0, it would be enough to cause damage to the HG. 3.2 with MLS gaskets has more ability to resist a temperature spike like that. On open deck engines, the real danger is if the bubble makes it to the open deck space around the cylinders because it will tend to just sit there. Under high loads it will flash boil to steam and cause an enormous amount of heat and pressure at that spot, rupturing the gasket and warping the head/block. On the 3.5TT, I believe it is a closed deck engine, so you have more protection at the level of the combustion chamber. Still, I think it is the right move to do the coolant flush and bleed procedure.
 
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does this car take special coolant? advisor told me it did, my research indicates it DOES NOT...
Your service advisor doesn't seem to be familiar with this car at all, unfortunately. The NSX takes standard Honda/Acura coolant, the same stuff as in my Civic. Also, there are only two bleed points, one at the front and one on the engine. Unfortunately, the one at the back seems really difficult to access; otherwise, it seems like a simple DIY.

I recall something similar for the 1st Gen NSX: one of the bleed points was below the air filter, which required removing it in order to access the bleed bolt. PITA for what should have been a simple procedure.
 
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I recall something similar for the 1st Gen NSX: one of the bleed points was below the air filter, which required removing it in order to access the bleed bolt. PITA for what should have been a simple procedure.
I've done it a bunch of times on my 1995 NSX. There are two bleed points up front and two in the engine compartment, and I never had to remove anything to get to them.
 
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yep, it's very odd too because the car stays right under the halfway mark (coolant gauge) when driving and then once i stop it creeps up to 3/4 then goes back down...so the bubble is moving around...I would think. Does anyone think that few seconds the gauge got hot could have caused any damage?

Based on that symptom I think that you may have something else besides air in the system going on so no need to get too worried yet. It may have nothing to do with the work you did.
 
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I've done it a bunch of times on my 1995 NSX. There are two bleed points up front and two in the engine compartment, and I never had to remove anything to get to them.
Mine was an '04 with the 3.2L engine, don't know if it had a different configuration, but I had to remove my air filter (it was an aftermarket one, which may have also made a difference). I distinctly recall being annoyed at that bleed bolt. All the others were easy to access, but this one made me almost want to skip it. Quite annoying.
 
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...modifying a car under warranty is playing with fire because no one at AHM wants to pay for problems created by parts and labor performed outside their franchised dealership system. Why would they? They think their engineering department is better at creating reliable parts than an aftermarket hobby shop, and, if nothing else, making more horsepower alone can create all sorts of unintended consequences.

And they'd be correct.
 
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