I have a high probability of going to a track day here next Friday at Thunderhill Race Park in Willows California north of Sacramento (anyone else going?). I'm concerned I may have overheating problems while on the track and need help diagnosing my problem.

My 2004 ZR is a 5AT, stock except wheels/brakes... but I fear the car was neglected by the previous owner so there could be a few things that need taken care of, the coolant system being one of them. The car has 67,500 miles on it now and I bought 1.5 years ago it was at 44K. When I got it, it had shot brake rotors and pads, and a broken A/C belt, all of which I replaced and gave it a nice oil change.

My main problem is, when doing hill climb runs when its above ~60 F outside, the water temp gauge gets to the top after about 10 minutes of hard driving. If I don't let off and let it cool, the 5AT will stick itself into 4th gear and stay there, even if I come to a complete stop. Cruise control malfunctions and wont engage (not relevant to the situation but could be to technical diagnoses). I don't get any other indicators on the instrument panel that something is wrong. I have to restart the engine to return for the transmission to normal operation.

The cars water temp is normal in all other conditions, including autocross (which is only like 40 second runs 20 minutes apart). It does fine when its 100+ F outside and the A/C is on and sitting around in traffic. When I took my car in for inspection at a Nissan dealer they said there may be a coolant system leak (but they couldn't find it) and wanted to do a pressure test which I skipped because I didn't have the cash.

I'm not entirely convinced this is a coolant system issue because it does fine in all other conditions... I'm wondering if the transmission is overheating considering how the transmission locks itself into 4th gear when the water temp reads near the very top.

So anyone got any ideas here? I am considering paying $70 to have a coolant system flush done at one of those quick oil change shops. Is it even worth it???

 

Time for a trans cooler, you need one to keep your auto alive.

 

Do you think that would be necessary at a track day event as well? There won't be any excessive up-hill driving. Can you share any technical knowledge that helps prove your statement?

 

Clogged thermostat? Much easier to check and to correct, if it turns out to be so! Don't invest heavy duty $$ in what may turn out NOT to be the problem, dude!

 

Your tranny heating up won't cause your car to overheat. Just check for your coolant flow to see if everything's circulating and that there are no clogs. Hopefully this helps

 

I'm not an expert on these Z's but I'm pretty good at cooling systems.

First thing to check is for air in the system, a good burp may be all that's wrong. To do this remove the radiator cap first and allow the car to warm up to temperature. Check your coolant level before it warms up. Once warm check it again, then have some one rev it up a few grand and take notice of the level. If it drops, fill it. Then let it idle down and repeat. Often time air get trapped into the system, on level ground it looks OK, but by the up and down revs you can "burp" the air out.

The next thing to check is the radiator cap, make sure it's puging at the right pressure. It should purge excess fluid at higher presures and suck the fluid back in when cooling, almost a self burping system. A screwed up overflow tank system can cause problems. Since it's not over heating during normal driving, I wouldn't think that the thermostat is bad or the flow is bad and with the up hill climb, the air will go to the highest location, your radiator.

 

I'll be there with the NCRC folks. Mag Black Z, not so base anymore. #415

Tranny cooler might not be a bad idea, but might be a bit late in the game for one now with the event in a few days.

 

Bleed the line and replace the fluid if you haven't already done so and try again this weekend, see how it goes. Take some temp readings after a few runs.

I'd also look into some better gauges, the stock gauges seem to have a delay and don't truely show where you're running temp wise.

 

His trans is heating up to the point it goes into link mode, and guess what the stock trans cooler is ..... in the factory radiator. Well after playing around with two FI auto's , one tracked. Auto trans in gerneral make a lot of heat under load and constant shifting.