I recently purchased a 1987 convertible. I'm not new to working on automobiles, however I'm new to the corvette world, and I'm perplexed by certain anomalies surrounding the C4. One being the higher operating temperature. With the research I have done I fully understand it and I'm willing to go along with it until it fails me. However my knowledge is that the cooler the better. So far the research I have done here has proven otherwise. Which leads me to my first question.

How hot is too hot? Both oil temp and coolant temp.

I would hate to doo so, but I would assume I hear hear it boiling it isn't good. I have seen several claims to 230* F coolant temp or so. I have observed on two occasions temps in this vette from the coolant around 240, and once it got up to 257 right as I parked her in the garage. At this point I could hear the coolant boiling back into the extra reservoir. The air temp was right around 100*F. I have seen oil temps as high as 226*F. The oil pressure was around 60-70 psi. I don't believe there is an oil cooler on it, but it may be hiding someplace I haven't looked yet. The thermostat, radiator cap, and radiator as well as the fan temp switches were replaced about 3 years ago. The previous owners had all of the work done at a dealership, and everything to my best guesstimate appears to have been done correctly. I'm not sure about the water pump, but in my experience when they fail it is very obvious. Everything about the engine and tranny feel and seem to run extremely well. No leaks and great pressures all around. I can't be more pleased with the performance of an almost 20 year old car. The vette has 105k on it, and appears to be very well cared for. I have all service records, and work done from 87' to date. I have taken the top part of the shroud off, and there is not any garbage between the condenser, and the radiator. The primary and aux fans are coming on when they are supposed to. I only saw these temps once, and I have tossed it up to the car has not had more than 5k put on it in 3 years, and the thermostat may have been stuck, OR the condenser (which looks cruddy) may be the culprit. I haven't run the car very hard, but I wouldn't mind opening it up on a desolate south Texas highway. I just don't want to turn her heart into a blob of metal the first time I stretch her legs a bit.

I have been a Chevy owner all my life, and have noticed gains in running other 350's at lower temps for 200k plus miles each, but am very hesitant to do so with this one.

Also the smog pump sounds like a hundred loose valves rattling, not sure if this is normal, and if a failure would be catastrophic enough to cause me to be stranded.

All that being said I have both the shop and service manuals for this year. I'm working feverishly on educating myself so that I can comfortably enjoy my new found piece of automotive history. If anyone would take the time to school me I'd be greatly appreciated.
Just trying to get acquainted.

Very Respectfully,
Champ909

 

Welcome! Lots and Lots of threads on the cooling system. Sounds like you are in the "normal" range. Do some searching on the subject. Sounds like a nice car.

 

Thanks for the welcome and reply. I did however discover three things that could have lead to my temps of about 260*.

One of them is water wetter. Some say it works some don't I'm now one of the believers. Don't know how it works, but it does.

The second thing I straightened what few fins that were bent on the condenser. I also turned the heater on and added more coolant. It appears when the previous owner replaced the radiator it was not properly relieved of the air pockets. They never drove it hard or far enough to notice the higher temps.

The third thing I found was the main cooling fan relay to be operating intermittently. I traced the problem to the relay. So I replaced the $4.00 part, and have not seen temps in either the coolant or oil higher than 225*. That is with hard driving, as well as sitting in traffic on a hot day with the a/c blowing cold.

If anyone else has this issue I would also recommend changing the engine oil, and tranny fluid, AND filters ASAP. You can bet with higher than normal operating temps they will break down considerably.

On to the performance threads.......

Very Respectfully,

CHAMP909

 

The 230* temp you see is normal and the fan(s) doesn't come on until 227*. Water boils at 212* so anything over that will boil and my 86 does when I shut down at 220*+. I wouldn't let it get to 235* with out showing some concern. Oil temps should stay within 15* range.

 

Pull the radiator shroud and the fans off and from the backside blast the fins out with a garden hose. Tons of stuff not normally seen will blow out and make a huge difference. Youll probably find a bunch of debris in front of the rad. also. Personally I like my cars to run under 200 if possible . The whole running hot part is for emissions..
Yes, sometimes the airpumps do make noise on these, unless its all the time I wouldnt wory about it.

 

While water indeed boils at 212*, when under pressure that boiling point is raised. Also the proper mix of water and antifreeze raises the boiling point further. So you can safely run well past 212* without boiling. Boiling can also introduce air to the system resulting in 'hotspots'. It looks as if you already have found and corrected some definite problems and all should be well now. Welcome to the Corvette fraternity and congrats on finding what sounds like a nice, well cared for one.

 

Water, not a 50-50 water and antifreeze mix, boils at 212° at atmospheric pressure (approx 14.7 psi), at sea level. Modern cars, for the last 50 years or so, have utilized a pressure cap, to allow the cooling system to pressurize as it heats up. The boiling point of water is raised, when under pressure. Eighth grade science.

I'd keep an eye on that A.I.R. pump. If it should freeze up and shred your belt, you could end up stranded. Even if you were to carry a spare belt, it won't do a lot of good with a locked up pulley.

RACE ON!!!

 

Straightening the cooling fins is a good idea and cuisinart's washing them is also good advice. In the extreme, you could do what Jet-Jock did and simply replace the radiator, but that's already been done three years ago, so you should be good for several more years.

Changing out those fluids is a very good idea; glad you did it!! And welcome! Watch that pulley, too.

 

http://temp.corvetteforum.net/c4/vad...erheating.html