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Phantom overheat

25 February 2012
Recently had some pretty serious electrical work done on my car. Picked it up yesterday and then drove about 100 miles over yesterday and today without incident.

On the way home from work today, however, I noticed the center channel (shift boot/coin tray/parking brake) were realllly hot to the touch. Temp gauge was normal. Obviously they are right above the coolant hoses, so I pulled over to see if the fan would kick on. It did, but pretty much as soon as it did, the temp gauge started rising fast so I shut off the car. Even weirder, this was with the targa top off but when I touched the top to put it back on, it was warm - not piping HOT as usual.

Let it cool off, put the windows down, turned the heat up and drove the rest of the way home with the temp gauge sitting at normal. The center channel did not heat up again.

Nothing leaking/dripping off the bottom of the car, no lights on the dash, fan running at idle as needed.

The only thing I noticed that was out of the ordinary was a ticking/clicking coming from the ECU area - behind me and to the right.

I wonder if there's an intermittent electrical problem (some pump failing to turn on) or if I'm just due for a new thermostat.
...and half of my coolant is missing. I wonder where it went, I can't find any leaks...
Going to try bleeding the system and adding coolant, and if that doesn't work, I'll have the thermostat replaced.
Clicking behind you and to the right is the main relay. Have you replaced it or resoldered all the connections yet?

If your coolant is disappearing and there are no apparent leaks you need to check your exhaust to see if it smells like coolant or see if there is an abundance of steam coming out. Sounds like you may have a bad head gasket.
Clicking behind you and to the right is the main relay. Have you replaced it or resoldered all the connections yet?

If your coolant is disappearing and there are no apparent leaks you need to check your exhaust to see if it smells like coolant or see if there is an abundance of steam coming out. Sounds like you may have a bad head gasket.

Main relay was just replaced along with aforementioned electrical work. I still have the old one so I can swap back and see if the clicking continues.

I will fill the tank back to the recommended level and keep an eye out for any steam or change in the exhaust smell.
Things to check:

-Coolant bottle: the stock "milk jugs" are known to crack on the bottom and leak. It's hard to spot because it can be a slow leak and the staining from the dried coolant may not be visible just looking at the area from the top.

-There are three rubber hoses that sit basically right underneath the center tunnel and connect pipes from the back to pipes at the front. They could leak, but it would be strange for them to leak enough to heat up the console without you noticing the puddle or smell.

-All of your hoses. If any of the electrical work happened under the center of the car, in the engine bay, or up front then if someone flexed an old hose, or nicked one with a tool, you could have a pin-hole you didn't before.

What I really think:

-It honestly sounds like it was low on coolant for whatever reason (maybe a slow leak), and got vapor locked. Opening the heater valve provided a different path and restored circulation. If you'd lost a significant amount of coolant via a HG leak, you would notice the white smoke more than likely, you would over heat more often, or start pushing coolant under load (e.g. you drive it hard for 10 minutes and it pukes coolant out the overflow).

(speaking as someone who's dealt with all of the above up to and including a HG problem...)
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Hmm... Exhaust smells normal and I don't have any abnormal smoke or steam. Electrical work was in the engine bay (alternator output wire frayed).

I just added coolant per the owner's manual but the car is taking *forever* to heat up while idling and the radiator hoses in front are still cool to the touch so I'm wondering if it's the thermostat after all.

Interesting thought about running the heater creating an alternate path... I never used it before.
I think I found the problem. LOL.

Looks like it's the tank. It ain't a slow leak, either. ImageUploadedByTapatalk1342898986.261614.jpg
if not the tank one of the hoses.......but if your car takes a long time to heat up then yes your thermostat is stuck open.
Letting it cool off before I top off the tank and crawl to Hilltop...

It never ends with this car. One of these weekends I'd finally like to stop troubleshooting and start driving!!
my coolant was slowly disappearing in my jeep for a while. A good inspection later, found the reason was because I had a very small crack in the head.
Unfortunately this seems slightly more dramatic. Let the car heat up enough (idle for over 10m) and coolant comes gushing out the overflow hose.

I have a feeling that I'm about to find out what it costs to replace the NSX head gasket...
Still could be a stuck thermostat. If you're not getting circulation through the radiator (which it sounds like you arent) the idling engine will eventually boil the coolant and cause the overflow. However, letting it do that does risk creating a HG problem if there wasn't one already.
Out of curiosity, what was the damage on your HG job? Or did you DIY?
I paid about 2 grand. Sorry. You better order the hg kit ASAP I think I got the second to last in the country.

Heh? Did they really discontinue such an important part?
Talk to Don at Hilltop. I paid $2400 on mine years ago to replace both HG. While he did that, he adjusted my valves as well and resealed everything. Also, it is the right time to add a header. No extra labor charge.
Car is at Hilltop. Valves were adjusted very recently and I already have CT headers installed.

A test on Monday will reveal if there is CO in the coolant, and then I'll know if it's HG or something else.
I'm curious of what serious electrical work you had done and most importantly, why?:confused:

There was a thread on it in this section a few days ago... Strange behavior under hard acceleration. I should have said lots of electrical troubleshooting, the actual fix ended up being pretty simple - removal of the extended alternator output wire left over from a previous owner's CTSC.

I know that during the troubleshoot the main relay was replaced and the ECU wire harness was disconnected and traced. I thought maybe this accidentally disconnected some sensor/pump/fan, but given how long the car takes to warm up (and always has) I'm guessing it was the thermostat which happened to fail shortly afterward.

Wish I'd replaced it sooner, before it (potenially) cost me a head gasket.
My HG bill was steeper than usual because I had Barney do about half a dozen "while you're in there" items. for just the HG, $2k - $2500 seems typical depending on the amount of machine work necessary to true everything up if there's any warpage.

Also, I wouldn't worry about gasket availability. Just get a set of MLS gaskets and call it a day. Not much cost difference from the factory gaskets (if it's an early car), but much stronger. That's the direction I went.

I will say that my HG problem (which was a small flaw apparently vs. a huge hole), didn't show up clearly on the chemical test which is why it took a while of it getting worse before I could truly diagnose it.
Probably worthwhile to go to MLS regardless of OEM availability, no?
Okay. I'm still hoping it's something other than the HG but as soon as I get the call that it isn't (bracing myself for the worst here) I'll order one from SoS.
And it's the head gasket. Awesome.

Hilltop is quoting me $3500 for the job, slightly less if I order my own gasket from SoS and ship it to them.

I imagine the bulk of this cost is the machine work for the warped head.