50BLKZ06

I have a 2003 Z06 that I purchased this past May (2013). It over heated the second day I had it on the road. It seemed to be fine after changing the thermostat. However, this was just a taste of what was to come. I overheated again and I replaced that thermostat in July. I made it all the way to September until it once again overheated and at that point I just parked it! I had only put about 4000 miles on it and had burned through three thermostats! I took everything out of the front of the car, the airbox, shrouds & radiator. I thoroughly cleaned the radiator & condenser fins (they were horribly nasty) and changed the temperature sensor, and once again I installed another new thermostat. The cleaning definitely helped. My cruising temp went from 202 down to 194! The car had sat in the garage for about a month while I slowly progressed through the repair. I have driven the car for about a month, including a few longer trips to other states, accumulating approximately 2000 more miles. Alas!! Today she blew again!! 4 thermostats now in 6000 miles over the 5 months I have owned the car! Has anyone else experienced this? Any ideas about what is happening??

bluestreak63

When was the last time the coolant was changed? Maybe start fresh with a 50/50 DEXCOOL/Distilled mix. Hopefully you don't have the green stuff in there now. Also, there is a procedure to follow so you don't get air pockets in the system, which from what I understand, can cause overheating issues.

PaConehead

How hot is getting? Under what driving conditions? 202 is not actually that hot. Cooling is not the strong suit of these cars; but have yiu checked the belts and water pump?

joenationwide

If you are truly overheating it could likely be a head gasket is blown. Thermostats don't just keep failing like that. I'd find a shop that can do a test.

fxdl

These cars will get a bit hot while sitting in traffic unless you keep the hvac on. This keeps the other fan moving. I'm in south fla and this is especially true in the summer. They just don't flow enough air at idle with the one fan on.

Paul 75 L82

I would have replaced the rad after the first thermostat. Your thermostat doesn't cool the car the rad does.

50BLKZ06

@ bluestreak63. The coolant was changed thoroughly with the first two thermostats. The third I did myself so I only replaced what I lost. Yes, the correct fluid (orange) was used every time. I did purge the system of air each time so that isn't the problem either.

50BLKZ06

@Paconehead, The temp is at 260 when I the check gauges light comes on and alerts me. It happens at random times, driving on the hwy, in the city, sitting in a car wash, etc. The engine usually gets up to about 205-207 then the thermostat opens and the new fluid coming from the radiator cools the engine down to 202. The 202 temp I was referring to was my normal cruising temp once the engine was up to temp and cycling through the system. After cleaning the radiator, etc, when it gets up to 205-207 the therm opens and it cools it down to 194 and usually holds there at cruising speeds. Cleaner radiator fins=more cooling of the fluid. I have checked the belts & hoses. I've only visually inspected the water pump for leaks. I have no idea how to check it operationally, but I assume it is working because after changing the thermostat everything runs fine for a couple months.

50BLKZ06

@Joenationwide, I don't understand how that could be related to my situation. It is really over heating. When the gauge says 260 and I pop the hood you can hear the fluid boiling and can see it as sometimes some of it makes its way out and makes a mess around the fender area around the reservoir. I believe a blown head gasket would create a constant problem, not one that allows the car to be driven with no problems for a couple months at a time, then once the overheating occurs again, a simple thermostat change allows everything to return to normal for a couple more months. Are you suggesting that a blown head gasket could be causing the thermostats to fail?

50BLKZ06

@Paul 75 L82, The radiator does indeed cool the fluid, however, it is the thermostat that allows the radiator cooled fluid to replace the engine heated fluid. Without the thermostat allowing the fluid transfer to take place the fluid inside the engine has no way to properly cool creating an overheating situation. My thought after the second one failed was maybe something else was actually blocked and causing the problem, but the problem went away each time with only changing the thermostat, albeit, for only a short amount of time. I have even bought each one at different places to try to eliminate the chance that maybe there was a bad batch in a certain shipment.

3sACROWD

I'm not an expert but I think the thermostat failure is a symptom and not a cause. I would be seriously looking at other components more closely. I'd start with the radiator.

Get the car up to temperature and then get under it to feel the radiator. You should feel uniform heat across the entire surface. (Be careful as the radiator will be HOT) If there is a blockage in the radiator, there will be a significant temp change in the blocked zone.

I had a car that appeared to have a good flowing radiator. Hoses got hot and you could watch the flow through the cap opening but the further down the radiator you ran your hand, the cooler it became. Top was too hot to touch but the bottom was cool enough to rest your hand on. The car would overheat sporadically over the course of days to months.

Another diagnostic would be to take your "failed" thermostat and put it in water. Heat the water to boiling to see if the thermostat opens. If the thermostat is a 180 degree, then it should open at 180 degrees. If your "failed" thermostat opens, it is likely not the cause. Newer thermostats might be reacting quicker than an older one and that may be why changing the thermostat is temporarily addressing your problem.

Paul 75 L82

I under stand how the thermostat works, on my high dollar hot rod motors I always just used the disc with the hole in it instead of the thermostat to make sure there would be no problem. I cracked a 383 stroker block because of a bad stat. But for every 10 threads about overheating I bet 8 of them are radiator problems. It's a really cheap part and easy to change out. The first overheating I have then that rad is history, but that's just me. I do live in south florida where it's hot all of the time.

joenationwide

A blown head gasket will cause overheating. And overheating will cause a blown head gasket. I blew a HG on my M3 and on the street it would never overheat, but if I did 2 laps on track it would overheat.

One way to check is this: in the morning, pop the hood and squeeze the upper radiator hose. If it is still highly pressurized from driving the day before, it is a likely sign of a blown HG. This means the leak is between the coolant passage and combustion chamber, so the HG leak was over pressurizing the system cooling system.

Someone suggested replacing the radiator. Thats a relatively cheap thing to replace to see if it fixes it, but I would just go to have a shop test the coolant for a blown HG (I think they look for hydrocarbons in the coolant).

Paul 75 L82

You can buy that test kit at the local auto parts store or NAPA. I used it to find a cracked block once.

RedZMonte

Possible causes, what to check for and how to fix: sounds like you have eliminated a couple of these possabilities allready.

Bad T-stat: high temps and over heating (1 stat go bad likely.. 2+ not likely the problem..) if you have a Drilled T-stat that will help run slightly cooler as well as help work out air bubbles. What kind of T-stat are you using?

Air buble in cooling system: Bleed and fill up engine threw to radiator hose

Radiator: remove and have inspected (could be crudded up on the inside).. replace

Water pump: Leaks, poor performance or noise.. R&R Pump (cheap insurance)

Head Gaskets: test for Carbon-Monoxide in coolant, pull plugs & inspect (cruddy plugs may indicate coolant in combustion chamber but not allways), Leak down test... replace HG's if bad

Did i miss anything?
S

50BLKZ06

@ 3aACROWD, That is what I've been suspecting as well. That is why I came here to find out if others have experienced similiar issues and what was done to correct it. Thank you for your advice! Your suggestion, as well as a few others on here, has been very helpful. These tips have given me someother areas to look at. I'll start on these today.

racebum

radiators on these cars are very easy to plug up. i changed mine with a new ac delco 20889 within a week of buying the car

the second thing is your fans, are they going into high speed at 230-235deg? forgot the exact deg.

also can you hold the car around 200 at idle if you turn the ac on? i suspect not? turn the ac on and see if the fans are running in low speed when you're sitting there at idle

HG is hard to blow on an LS engine. can be done but a plugged rad & fans not working would be MUCH more likely

so much debris gets jammed in the fins of the rads you can either pull yours and blow and scrape it all out, or, buy a new one. i bought new simply because rads don't often live past 10-12 years and 100k miles, at least not these plastic end cap ones.

50BLKZ06

thanks for the replies. I have taken the radiator out and cleaned the fins very well. However, it was a mess! It had so much grass stuck to it that it stunk horribly! So given the info you just posted as well as others on here I will replace the radiator next.

C5Z06CE

You can relatively easily check for blown HG or cracked block by pressure testing. If I recall correctly when I was concerned about this in my last car Advance Auto and AutoZone will loan you a pressure tester for FREE. You hook it up to your radiator cap and increase pressure and hold pressure steady. If the pressure drops on the gauge,....you have a leak of coolant into your engine and therefore poor flow of coolant in your car causing overheating. It is caused by blown HG which is relatively easy or a cracked block....but not so easy for a cracked block as you know. If I were you before you spend money on a new radiator I would do that to make sure you don't **** away money on a new rad. Since it is a used car that you bought recently you may not know how the last owner treated it. Even though it s PITA it's cheaper to do that with a new round of coolant and put your radiator back in. If it leaks pressure sell the car,... If not buy a new radiator.

Just my .02

racebum

agree for sure, don't install the new rad till you know you don't have a pressure leak in the hg from those 260deg temps

if you do you could pop the new rad as the system goes over pressure

radiator pressure test isn't a hard thing to do. you basically pressurize the coolant tank and see if there is any loss