Okay, since the temperatures have gone way up recently (i.e. high 80's to low 90's and very humid) and I've been doing a lot of rush-hour traffic type driving, I've had what seems to be some overheating problems on my 72 L-48. The car has never given me any kind of problem like this before, but with all the bumper-to-bumper traffic I'm having to deal with, the car will overheat sometimes...it gets to the point where the moment I push in the clutch, the engine will start to die and I have to rev it up to keep it running. Today it actually didn't happen until after I had turned off the car for 5-10 minutes after a highway drive (which was after rush-hour driving) - when I got back in the car and fired it up, it immediately started to die.

So, basically I'm looking for some kind of checklist as to what I can do/check to cure this overheating problem. I'm thinking I may as well replace the coolant ASAP, since perhaps there's a bad coolant to water ratio, and I don't know the last time it was changed. What else should I start checking/getting serviced/replacing and in what order?

Thanks in advance

*edit* BTW, I'm still running the stock fan/radiator/water pump set-up...

 

My car has the same problem...

Since the overheating problem has slowly crept-up over time, it's possible that the radiator is beginning to loose it's efficiency and that it's time to have it serviced.

Are all the shrouds still in place? If the temerature is high but stable, I'd guess that your thermostat is ok, but it's cheap to replace it anyway.

There have been some good threads lately about this same issue...can't remember titles right now???

There are some pretty savvy vette owners on this forum, so I'll be watching this thread closely.

Good luck...

 

Check your clutch fan..engine off.....(it should have kicked in.)..rotate it by hand slowly (360 degrees) and if you feel intermittant resistance,it is toast...next, just change the thermostat...cheap....you did not mention temps or if you smelled coolant...more info would help...btw,if your fan wobbles then you must suspect the water pump as they share the same shaft...

 

Another way to check the clutch fan start the engine and then shut it off. If the fan stops after a couple of rotations it's OK. If it keeps spinning, it's toast.

 

I don't know what kind of reading you are getting since you don't mention it. Your car came from the factory with a 195 degree thermostat. I would replace the one in your car with a new stat and gasket to start off with if your fan clutch and water pump are ok. Most fan clutches when they go bad freeze up or start leaking hydraulic fluid. When they freeze up you will hear a chopping sound with the engine running and of course with the engine shut down won't be able to spin it by hand. When the engine is shut down grab the fan blade and see if there is any wobble in the water pump. Usually if your pump is going bad you will have a leak right under it out of the breather hole under the pump shaft.

When you replace your stat you may want to flush your system and put a fresh 50/50 mixture of a name brand green antifreeze back in. Make sure you buy full strength antifreeze. The big gimmick by the retailers today to keep the price down is to sell premixed antifreeze. Don't buy this type of antifreeze. It actually will cost you more in the long run. Buy full strength and you mix it on its own with water. Usually when I flush my Vette it is good to put it up on 2 jack stands and open the two plugs on each side of the block. You may need to cut a metal coat hanger to open the drain through the gunk you will find when taking out the plugs but you get a better flush by taking these two plugs out while flushing the system. This way you get all of the old antifreeze out of the block. Most of my cars I just leave the garden hose in the radiator while the two plugs are out to flush the system. Then you could fill the the radiator up reinstall the plugs and let it run for awhile and then take the plugs out again to drain before installing new antifreeze. Buy yourself a quality thermostat also. Either Stant,Robershaw or Delco is what I use.

A word of advice. Don't over tighten the thermostat housing or you will break it. Make sure you use a sealant on the gasket. I still like to use #2 Permatex, some use silicone. Also when taking out the two plugs in the bottom of the block and running the coat hanger into the hole be careful because the old antifreeze solution could be pretty hot and you don't want to chance getting burned once the coat hanger breaks through the gunk. The two plugs are located just above the oil pan, one on each side of the block. Just unscrew them out and get your coat hanger ready.

Fred

 

1) Plastic chin spoiler, bolted to lower valance. Increases air flow at higher speeds
2) Valance seal, rubber seal that directs flow over front crossmember cover plate.
3) radiator to support seals, foam
4) hood to rad support upper rubber seal
5) shroud to radiator seal
6)Lower rad hose, be sure it isnt collapsing
7) rad flushed and good flow
8) fan clutch
9) shrouds had extensions in place
10) thermostat
11) water pump belt loose
12) check engine ignition timing too

 

Thanks a ton for your replies guys, I'll start checking those things out right away.

Sorry for not mentioning the temp it's running at...it's because my temp gauge is...well, rather questionable It's never worked before, but for some reason in the last few days it's started working...I don't know if I really trust it enough to get an absolute reading out of it, but it has read close to 200*...

 

why is it no one else can identify a carb percolation problem? didn't take auto shop?

 

200 ?? Get an instrument and check temps against your gauge....Replace that thermostat as I mentioned anyway....if 200 is true,you may be ok,but flush,and make all other checks ....

 

I put in a 180 degree thermostat, made a big difference.

Another way to check your fan clutch - spin it by hand as hard as you can. If it rotates more than 270 degrees it is worn out.

 

I agree with Matt, could be vapor locking when it gets hot. My .02
Bernie

 

I hope nobody minds me jumping in.
But I have the opposite problem. last summer I was running around 200-210, I had the carb rebuilt(thats it) and the car runs great now but the water temp gauge never moves above the 155 tic mark on the gauge. The engine does feel cooler but I think the gauge could be off 10-20 deg maybe more. How can I check to see if gauge is working at all?

 

A 180 stat is fine but most later C-3's came with a 195 stat and unless the 195 stat is used supposely it will effect the emissions on these cars from what I understood over the years. The claim is that GM build the car emmision wise to run at 195 degrees. During the 60's most cars that were pre-emmission came with 180 stats. Alot of car buffs back then would change to a 160 stat for the summer driving.

 

Go and get yourself an IR Gun to shoot your engine for the correct temp. I think you are suppose to aim it at your upper hose to get the correct reading to compare to your inside guage.

 

Meh, I don't care too much as far as emissions go, we don't get smog tested over here in Cheeseland Guess I'll go get a 180...

 

That is the only sure way...by hand..I don't buy into the "run engine" "shut down" method" as it is not reliable...by hand you can feel resistance and where it is "free" and know for sure there is a problem...good tip by the way...

 

Yup, higher engine temps = less oxides of nitrogen in your exhaust.

 

If everything is right under the hood you should have no problem with overheating using the 195 stat your C-3 came with. I still use a 195 stat in my 73' Coupe.

 

Good sound advice for all Vettes after 1968 as cars are our business. 195`s are correct all year around.

 

You can take readings right off the thermostat housing...I have a 180 degree and with engine running it read very close to gauge..at 178-180...within 2-3 degrees...important to understand thermostats "modulate" depending how close temps are to rated (calibrated) spec of stat...so readings will vary as thermostat "modulates".