Hey guys new to the forum! Just bought a really nice 1979 l82 corvette. The only problem i have is overheating. I drove the car home and as soon as i shut it off, the over flow started pouring out coolant all over the floor. I thought it was maybe low on coolant but isnt.i put some in and I took it out today for a 15 min drive and brought it back and did the same thing! I measured the temp and its at 230 degrees. The idle after 10 mins of running after startup is 195. Any ideas? Just flushed motor today. Thanks!

 

Does it still have the OEM 5 quart coolant recovery tank? If so make sure the tank's COLD level isn't overfilled. At full operating temperature about 3 quarts of coolant get pushed into the tank so if its overfilled to begin with the extra will get pushed out onto the floor. The tank is clearly marked COLD about 1" up from the bottom. If its not being overfilled by you it could be a leaking head gasket (maybe why the car was sold) and you can buy an inexpensive tester to check for a blown head gasket from any AutoZone or other automotive parts store.

 

Yes it still has the stock tank and everything. And i made sure to only fill it up to the "cold". Also forgot to mention, the is alot of white stuff in my radiator around the ports. Any idea what that is? Also, if it was a head gasket wouldent i be blowing smoke white out the exhaust? It runs great and isnt doing that at all.

 

I would check that the thermostat isn't stuck or partial restricted . Check. The timing and while you are at it get Lars' papers.check to see if coolant is circulating. There are more than a few things to check. A cooler thermostat maybe a good. Idea these cars run pretty warm for the most part. I put an aluminum radiator in mine and getting hot is no longer an issue withThis car. Good luck, you will get lots more info, soon.

 

Thanks. Already replaced the thermostat to a 195 and still have the issue.. how much did the aluminum radiator help?

 

195 is too hot, I know some argue that but it is just too hot. A 180 should be your highest. The aluminum radiator helped a bunch like about 40 degrees. Your engine timing on those engines is critical a d factory specks ARE BAD for temprature. Set it up per Lars papers, drivability fuel economy and power will be affected too. I can't overemphasize fits importance.

 

The 78/79 L-82's are notorious for running VERY hot-225-240 degrees is(with AC running.90 degree day-on the highway) common-wonder why the 882 heads are known for cracking????. Mine ran these temps day one totally stock. I have done too many changes to list here over 30+ years to finally eliminate the problem to list. As others have stated, timing, emissions, running lean, need to be addressed first. If the car has the OEM y pipe exhaust with a cat, get rid of the whole thing and run 2.5 inch duals with no cat-helps the engine run cooler AND adds lots of HP. An aluminum radiator, aluminum stewart stage 2 water pump, 180 thermostat, and proper hood /radiator insulation along with a lower chin spoiler extension will eliminate the issue if everything else is correct. My OEM L-82 after the changes and New L-82 355 (rebuilt to high performance standards) never goes over 175-180 today. Only took me 25 years to correct the problem....

GM knew that there was an issue with high temps (only way for the L-82 to pass emissions). The 78 L-82 temp gauge at the 12 O'Clock position on the gauge is 200 degrees. Since the car ran a routine 225 degrees, the gauge always ran at the 2 O'Clock position making drivers question the temp and gave GM headaches. In 1979, the L-82 had a different temp gauge with the 12 o'Clock position now showing 220 degrees, not 200 degrees, added an electric cooling fan inside the engine bay in front of the mechanical fan deep in the shroud for added cooling, AND added the 4 inch flexible rubber extension to the factory 78 chin spoiler for added cooling for the L-82's with heavy duty cooling...Hmmmm...

The issue can be corrected but will take some time, money, and effort. The OEM L-82 and the new L-82 355 both have no cooling issues after my long trek to correct this factory defect...

 

My '78 was (is?) an L82. However the P.O. cooked the motor and replaced the block and pistons, everything else is OEM parts.

Mine is an A/C car, so I have a bit extra restriction. Mine runs 200* on the gauge all day long. I have a IR temp gun, but oddly Ive never checked the Tstat housing with it. I guess I should.

I'm going to pull the a/c rad to allow the extra airflow. A/C isnt working anyway, no compressor. Might be something for you to check on as well.

dodosmike

 

Agree with JB78L82 post.

I owned a black 79 L82 4spd w/AC in 1980 . It was practically new when I got her. Had stock exhaust too.

It was hotter than the throws of hades . Ran 225 *F most of the time or higher when the AC was on.

My sneakers feel like they was gonna melt.

So ....I think I saw few days back, anther guy was asking about the solenoid cooling door that let's additional air from bottom up I and in. Might want to check that deal out. Funny, I never remember that on my car , but I guess it was there.

My 79 had the factory plastic spoiler chin "with" the additional factory rubber air dam . This was riveted on to the plastic regular chin spoiler .
It provide about 4 inches depth more air scooping. And YES it makes a difference. The first ones were used on certain 73-74 LS4 Cars.

These air dams are really low and get torn or battered over time....so you may have had one once apon a time.

I have found washing the fin s out with hose can help, I guess air would work too , to get the dirt and bugs out blocking air flow .the front intake side of the rad.and the condensor coil sits in front of it ....clean that too.

If you can , or permitted ...by your state. .....I'd go with true dual exhaust , non convertor, no smog pump , and use a 180 degree t stat.

The cat convertor and choked pipe though it killed the L 82 breathing.

I did all items above, de smogged , increased the timing retuned ......it probally had 25 -30 more HP with that alone.....stock exhaust manifolds . It ran strong for a basically stock 79.

 

Change that stat to a 160 and go ahead and buy an aluminum Rad and electric fan setup. I did this to my 79 and temps stay cool at all times. I use a 185 temp switch for fan activation too. Good luck

 

After timing and exhaust, aluminum radiator, Stewart aluminum stage 2 water pump (180 Robertshaw modified thermostat), and spoiler extension will solve the problem with a mechanical fan...no need for electric fans.

 

I agree with a 160 T stat, but some go nuts when you suggest that.

 

I like to go back to basics. You changed the thermostat to the stock setting. That's one problem done. As mentioned before, is all the foam and shrouding in place? Then check the obvious. Take the cap off on a cold motor and run in. Watch for the thermostat to open and then water pump circulation. Once that is good. Shut it down and check the clutch fan. Make sure it has a lot of resistance with a hot motor. If it spins easily, it's bad. Then check the cap or squeeze the radiator hose for pressure. You need pressure to drop the boiling point. Last, make sure it's full. I usually point my car on a steep up hill part in my driveway, start the car with the cap off and top it off. If it starts puking, slap the cap on and watch the overflow tank. 9times out of 10 it's one part of the system that's not right. It could even be timing too far retarded. So at idle, no problem with vac advance but put a load on it and the vac advance is no longer present, poof , running hot within a minute.

 

gee mine has always run 200-210

 

Would any 3 row aluminum radiator be fine? Is there any specific one? I have found some for around 180 bucks.

 

The thermostat only controls the minimum temperature and has nothing to do with the maximum temperature because only the fan and radiator controls that. And the L-82's didn't operate at a temperature any higher than any of the other 350's. With the heavy duty 4-tube radiator and 7 blade heavy duty 7-blade clutch fan the normal operating temperature was/is 195 to 200 degrees but will hit 210-215 in stop-and-go traffic with the A/C on just like my '71 with it's 454" and A/C does.

In the 50 years I have been twisting wrenches for a living and for a hobby I have found the usual cause of "overheating" has been the use of a wrong temperature sender.

 

Did you read post #7 and #9?...78/79 L-82's absolutely did NOT run the same temperatures as other 350's including the 78/79 L-48's...not even close from the FACTORY. Not only do I have first hand experience from my 78 L-82 that I have owned for 32 years (25,000 miles used-bought TOTALLY stock in 1983) but also I have known several other 78/79 L-82 owners who had their cars since NEW and the car's normal operating temperature was 220-225 on a COOL day-235-240 on a 90 degree day with the AC on, even with the 4 core brass radiator, auxiliary electric cooling fan, and heavy duty clutch 7 blade mechanical cooling fan .

 

Found out my radiator is bad! For some reason there is a large dent in the lower half restricting flow. Also very dirty and battered up. Going to go pick up a new aluminum one tomorrow and go from there. Ill post when its done!