jbrun

Hello,
In a previous thread I am trying to finish up 3 yr restorationon on 61 but car continues to overheat. It's a fresh rebuild. All new hoses, water pump is pumping good, new expansion tank cap with original expansion tank, radiator is not brand new but was hardly used- flushed radiator, was having trouble with my temp gauge so put temporary new temp gauge in with its own sending unit. New fan clutch. Tried 3 new thermostats so finally took out so its still running hot 210-220 with no thermostat. It has good coolant flow so I'm hoping that engine builder didn't block water jacket with head gasket. Timing was set but am going to double check that. I've been itching to get it on the road but am at a loss as to why its running hot. I've owned the car since 1965 and never had overheating issues. Not sure what to do next.
Thanks for all the posts and info I've got from this forum. I really appreciate it.
John

John S 1961

Really 220 is the upper limit of OK..... But 230 is too hot, If you live in a high ambient temperature environment say plus 90-95 then that may be acceptable. Will it overheat idling or on the road cruising, or running up a hill at 75 or at night when its cool? Describe its behavior for us.

jbrun

I took it out today-nice cool day. It got up to about 195 driving at about 30mph- so turned around and came home. Ran for few minutes in driveway then climbed to around 210. I'm afraid of causing damage if I keep cruising. Should it even get that hot with no thermostat in it?
Thanks,
John

John McGraw

The thermostat does not control the maximum temp, only the minimum temp. A wide open T stat, or a completely missing T stat should be about the same. Have you checked the temp of the T stat housing with a IR gun to assure that it is really running that hot? The sending units from the parts stores are notorious for reading too high. At 220 or 230, you radiator should be boiling over. If you are not boiling over, then it is a pretty safe bet that you are not as hot as your gauge says it is.

Regards, John McGraw

boxster99t

If you haven't already done so, check out John Hinkley's Restorer Article on 63-82 Corvette Cooling System (here is a very slow downloading link to a copy http://www.metroli.org/pdf/WHITE%20P...0Operation.pdf ).

Thermostats (unless they're stuck closed) won't be your issue. It will likely be the radiator, fan clutch, or engine timing issues.

jbrun

John,
I have an IR gun and gauge seems pretty close to what gun is saying. It did spew out expansion tank so I put new cap on. It didn't come out of overflow like it did before when it got to about 210-220.
Really anxious to get it completed.
Thanks,
John

jbrun

Boxster99t,
Thanks for info. I will check it out.
John

boxster99t

John M., I agree on checking with an IR gun, but not on boiling over.

Unpressurized water boils at 212 degrees and a 15# radiator cap should raise the boiling point roughly 45 degrees to 250 plus degrees.

It should not boilover at 220 or 230 unless the cap's not holding pressure.

Sky65

Please give us your engine timing process and current setting specs. Manifold or ported vacuum source, vac advance, mechanical advance and initial advance setting. Not saying you did it wrong but it is amazing how much timing affects engine temp.

Tom

Vet65te

When it hits the 220 mark, does it stop there because you shut it off or do you get the feeling that it would continue to rise if it continued running? Also, is this a slow, steady climb or does it quickly come up?
The list of 'suspects' is long and it sounds like you're checking out the easy to deal with items first. Do you know someone with a cooling system pressure tester? Good kit to have to verify radiator caps (although you've already replaced yours and that didn't seem to make a difference). Hooked up to the expansion tank, you might see some indication that you've got combustion gases present from the recent rebuild. There is a relatively cheap way to check for combustion gases and that's to pick up this kit from your local NAPA store. Test fluid is a dark blue to begin with. If after a minute of drawing up the vapors from your radiator/expansion tank (with coolant level dropped so there is no splash to contaminate the test results), you see the fluid turn yellow then that's usually in indication that you've got a compromise somewhere.

Mike T.

midyearvette

best post so far.....

56Heap

Also verify that what you're using for TDC is actually TDC. Your dampener may have spun or you have the wrong one.

jtranger

If you are still running a copper or brass radiator it is probably the culprit.
Get an IR temp gun if you do not have one and see how hot the radiator and other points are heating up.

I had the same problem with my '61, spent money and pulled out my hair doing everything except replacing the radiator. Put a Dewitts radiator in for about $500.00 and now the car barely gets to 180*.

Best money spent especially if you have a new motor like I did. The cost of the motor is much more than the radiator.

Good Luck

jbrun

Jtranger,
I've been using IR gun to make sure gauge is accurate. My radiator is aluminum however it was not a brand new one. I put clear hose on upper radiator to make sure I had good flow of coolant. It was pumping good. Maybe it is radiator. I checked Dewitt's site and may try that.
Thanks,
John

Redbird

Expansion tank should not be over half full.

kabong

This is exactly what I did. I fought cooling problems for years and then I bought a DeWitts and problem solved. I get caught in traffic and it doesn't ever overheat.

BobT59

I, too, wrestled with a severe overheating problem in my 59 (w/327ci)for years....made it undriveable... finally spend the $$ on a Dewitts. It might now reach 180 on a hot day....

SS409

Now that's a clever idea. I'll have to remember that.

AZDoug

Clogged radiator doesn't mean it won't flow good.

What is means is that the water is just going down one narrow channel from one corner to the other, and bypassing 80% of the rest of the radiator.

Doug

Chuck Gongloff

That's a point that MANY people don't understand.

Also, because it doesn't leak, it must be good.

Chuck