Help - leaking coolant

'98, stock except for headers / exhaust. Owned since this July.
Prior to selling, PO did significant service - performed by Autowave, a popular local NSX specialist - including hoses, tank and more...

I've driven approx 6K miles since purchase, with zero issues.
H2O temps have remained normal throughout events below.

About four weeks ago, I noticed a few drops of coolant on the garage floor.

A couple of days ago, while driving to an appt, I noticed some white smoke from the back of the car less than a mile from home. Returned home, grabbed the truck, parked the car. Later, checked under the car to see a few drops of coolant. Looking from underneath, saw a couple of damp areas on the pass side. View from top, looking down revealed nothing. Tank was about a quart low. Note: the tank still had some pressure when cap removed.

Sat, took a quick a quick spin to check things out - prolly less than 2 miles. Not really any smoke in the mirrors, but when I got home - car was leaking coolant. Shutdown in the garage, coolant continued to come out - from the passenger side of the engine area. Hard to see exactly where from...
Coolant continued to leak (small steady stream) until I removed the coolant tank lid. Tank had a lot of pressure built up. This isn't normal is it? Leak stopped when pressure relieved...

I've worked on my own vehicles, but no motor work on the NSX. Is this serious? Head gasket issue? Is something perhaps causing over-pressure in the system forcing the leak?

Hoping this is simple fix

Before you jump to conclusions about a head gasket, track down where the leak s coming from. On the passenger side there is the water pump/its hoses and hoses going to the oil cooler. If you have trouble seeing where it's coming from , you can use a black light/dye kit to track it down.

Sounds like one of the small hoses around the oil cooler area didn't get it's clamp installed. The pressure cap on the cooling system should relieve pressure above 15 LBS.

First check the 2 hoses going to the oil cooler (immediately above the oil filter - pull the rear wheel off to see them clearly). To find the leak, let the engine run until you see the coolant coming out - that should be fairly easy to spot. Pressure in the tank is normal.

Thx, guys.

Will jack it up and crawl under tonight. Will post my findings.

Have you checked to see the coolant tank? This sounds like what was happening with my car when I first bought it. Coolant tank sprung a leak on the top seam and only leaked when car was warmed up.

gt_nfr said:

Have you checked to see the coolant tank? This sounds like what was happening with my car when I first bought it. Coolant tank sprung a leak on the top seam and only leaked when car was warmed up.

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The OP was pretty clear that the leak is on the passenger side of the car. When the overflow tank busts a seam the resulting leak is on the driver's side of the car.

I jacked up the right rear and pulled the wheel.

Oil cooler lines are not leaking. Might be the water pump, but it's beyond what I can see / do with my current garage setup...

Flat bedding to my mech today...

So what is the diagnosis? I had a similar issue and it turned out being a blown head gasket. Not fun.

So head gaskets do fail on these cars..?

The white smoke has me fearful of this. No oil in the coolant tank, and no water traces on the dip stick though. Hopefully will get it to Ramon today.

You can check the coolant tank for oil and the oil for coolant. The white smoke had me thinking that with your first post. Trying not to be negative and that is why I held off on my guess. But yes these cars do blow head gaskets. I assure you.

Well, my worst fears have been confirmed.

A headbolt has pulled, resulting in failed headgasket.

Was very disappointed to hear this, as I had long thought these engines were bullet proof. Potential costs of new block and rebuild swirled in my head and I was not a happy NSX owner.

Well some research - much of it on Prime, and contacts with Prime based Shops - has revealed this is not that uncommon.

Additionally, there is a relatively simple fix, that actually is an improvement. TimeSerts. I've decided to timesert all sixteen headbolts, and replace all headbolts with new. Not really that expensive to do...

Same exact thing happened to me and that is why I held off until the end of the thread to chime in. Mine pulled two head bolts so I timeserted every last one of them. Seems this is happening on the 3.2's but not on the 3.0's.

Have you got your car back yet?

I'm sourcing the new head bolts and serts myself.. I should be dropping parts off tomm.

Hopefully, will be back on the road soon.

I was more fearful that the block was flawed, or the motor had been abused. That does not appear to be the case...

Doesn't seem to be much of a reason why they go. That is the odd part. OEM head bolts are meant to stretch a little and you would expect that give to compensate for any expansion. The way these bolts just pull the threads right out of the block is a bit of a concern.

Good luck and looking forward to seeing you at the next meeting.

I'm trying to learn more about what caused my own head-gasket coolant leak. It's a 3.2L that has run a standard Whipple CTSC for all of its 39k miles. Looks like I will also be doing the TimeSerts with the rest of my rebuild.

jwmelvin said:

I'm trying to learn more about what caused my own head-gasket coolant leak. It's a 3.2L that has run a standard Whipple CTSC for all of its 39k miles. Looks like I will also be doing the TimeSerts with the rest of my rebuild.

Click to expand...

make sure to have your heads checked for warpage as well. they may need to be resurfaced.

I also had a blown HG on my 3.0. In my case, the entire head lifted. It is not that the HG is a fault on the NSX, it is the cooling system. Especially on the NA1, a coolant problem can result in air getting to the block and flash boiling the coolant, which causes huge steam pressure and either tears the gasket or, in my case, lifts the head. That is why all the experts (LarryB, Kaz, Shad, etc) are so insistent about making sure your cooling system is bled correctly, has no leaks and is topped off. Kaz especially has shown over and over that even cars that had the system thoroughly bled per the factory manual have air pockets all over (especially at the heater core and radiator). As far as the head bolts pulling, the NA2 does have a higher torque spec vs NA1- 76 lb/ft vs 55. Might be a combo of the higher tension plus a steam issue overcame the strength of the aluminum threads.

Interesting info. Is there a recommended procedure out there for ensuring no air in the cooling system?

Returning to my old thread...

Since the time-sert install, I've had zero issues. Call me happy, but it was a pain to sort out.

My mechanic - well respected in these parts - has this opinion:
These cars in many cases do not get driven a lot, and when they do they get driven hard. The heat cycling in the block and heads - over the last 15-20 years - can/may cause stress or slight distortions that can cause the metal at the threads in the block to weaken.
I do not have the experience to have an educated opinion, but this may have some truth...

Yes- Kaz has it on his blog somewhere, but can't find it right now. Basically, you do the factory bleed routine and then a few extra steps. Kaz himself uses a vacuum filler for the coolant and then does his factory+ bleed routine. He has noted air in the systems of NSX's that has been in there for YEARS. This is also why so many NSX's burp coolant at the track. All that 8,000 rpm driving pushes out those air pockets. Kaz says it is due to the unusual layout of the NSX coolant lines. The water comes in the bottom and out the top of the radiator, so any air bubbles must be pushed down and then under the car. It's air so it just wants to go up, meaning it is very tough to get all the air out in the front of the car.

i remember our local nsx mechanic,the late steve gooding,telling me that part of his air bleeding procedure involved jacking up one end of the car at a time,and leaving it that way for a while.somehow the height differential aided in the process of getting the air out.

[MENTION=18194]Honcho[/MENTION], would an air bubble like you describe prevent coolant flow or just create a local hot spot? In other words, could a bubble cause an issue without the overall engine overheating?

I would e-mail Kaz to confirm, but I have never heard of an air bubble blocking coolant flow. The issue is the air creates an environment for steam to flash and it is the superheated steam that does the damage, not the air. It could occur in a local hot spot (this is usually what punches through the gasket and warps the head) and your gauge might not show the spike until after the damage is done. In my case, the air bubbles collected around the tops of the cylinders and just floated there. During normal driving, nothing happened, but under stress and high rpm, the temps caused the steam to boil, flash and lift the heads uniformly. That is why I was able to drive the car for months without noticing a problem. My temp gauge never budged. It wasn't until I hit the track and on the back straight at 7,000 rpm of lap 4-5. At that point enough heat built up to lift the heads, blow out the coolant from the overflow tube, and make my gauge hit the red almost instantly. Crazy enough, I was able to drive the car home without any problem. Kaz had two cars in the UK that had the exact same issue.

My trick on getting out the air bubbles is I have a long steep driveway. I put the car nose down the driveway and repeat the air bleed in the order specified in the manual. I've never had a problem in 14 1/2 years of ownership. I don't track the car, but have driven it at the old Kid's Day at the Glen. Over an hour period, rev's only dropped below 6,000 when I dropped off one kid and picked up the next kid. Engine/drivetrain is 100% stock.