1976 Eldorado Convertible - Engine Temp

[MIKE2CADDIES]

I have a 76 Eldo Conv and was wondering what the correct operating engine temperature should be ? Had engine rebuilt and radiator ( 3 core ) is fine, fan clutch fine , thermostat is fine but overheating ?? Going over 260 and baffled. Mechanic who had engine rebuilt said I need high efficiency radiator since rebuild increased hp.

[Scot Minesinger]

Well no confidence in that mechanic.  For overheating:

1.  Fairly certain you should have a 4 row radiator, not 3.
2.  The thermostat should be checked to make sure it is good.
3.  Make sure timing is properly set, the distributor could be a tooth off too.
4.  Make sure exhaust heat riser is open after warm up
5.  Make sure snorkel damper is open to draw air not across exhaust manifold
6.  Be sure exhaust is not plugged - they can look fine on outside - take vacuum measurement

Betting it is items 3 or 6 based on rebuilt engine, and of course for sure item 1.

[Jeff Rosansky CLC #28373]

How and where are you measuring the temp? Other than something telling you it is hot, are there any other symptoms?
There should be some sort of baffeling to direct the airflow thru the radiator. Is it all there?
Jeff

[MIKE2CADDIES]

I had a temperature gauge installed and it is in the glove box. It was all the way at the end ,which is 260, and the engine block - radiator - radiator hose and overflow tank where boiling like a tea kettle.

[m-mman]

First and easiest check.
Car warmed up and running. (but not at 260 degrees) Remove radiator cap. Look into radiator
1. Can you see any water/coolant? Was it filled properly and had all the air bleed out?
2. With engine running water/coolant should be squirting/flowing freely out of the tubes that are the radiator.

If you cant see water FLOWING (maybe the radiator is filled to the brim), as you increase the RPM slightly it will draw more water in and lower the level enough to see the tubes and check for flow.

No flow? stuck thermostat is the likely culprit. But tell us what you are seeing.

[Jeff Rosansky CLC #28373]

I know this may sound simple, but check your radiator cap. I did my engine, accessories, etc----but forgot my cap.
Jeff

[Steve Lomas]

I had a temperature gauge installed and it is in the glove box. It was all the way at the end ,which is 260, and the engine block - radiator - radiator hose and overflow tank where boiling like a tea kettle.

Does the 'coolant temp' light come on? Does the reservoir overflow?

I've driven these cars frequently for a couple of decades.. I've never know the radiator hose NOT to boil on turn off, after anything more than a couple of miles on a cool day.

[TJ Hopland]

I've driven these cars frequently for a couple of decades.. I've never know the radiator hose NOT to boil on turn off, after anything more than a couple of miles on a cool day.

Interesting statement.   I have only had it happen when there is some sort of leak and the system is not holding pressure.  Gas boiling out of the carb, that was often a problem.    I was just screwing around with my 73 last week in the driveway and noticed the gauge pegged at 260.  Ran it at high idle for a minute or so and it started to drop but stalled due to a wiring issue.   I was poking around under the hood right after it shut down and after the AC quit hissing there was nothing but some metal expanding noises.    I really expected to hear some coolant like noises but it was quiet.   50/50 at 14-16  psi should boil in that 260-275 range.   

[Steve Lomas]

Interesting statement.   I have only had it happen when there is some sort of leak and the system is not holding pressure.  Gas boiling out of the carb, that was often a problem.    I was just screwing around with my 73 last week in the driveway and noticed the gauge pegged at 260.  Ran it at high idle for a minute or so and it started to drop but stalled due to a wiring issue.   I was poking around under the hood right after it shut down and after the AC quit hissing there was nothing but some metal expanding noises.    I really expected to hear some coolant like noises but it was quiet.   50/50 at 14-16  psi should boil in that 260-275 range.

I don't have a leak as far as I know, but whether everything else is working as it should...  I'm not entirely sure all my vacuum lines are good and connected properly so it could be something is off,  but both my Eldorados- a 75 and 76 always did this throughout all kinds of tinkering.

Gas boiling out of the carb is something I'm wondering about..  The 76 always started right up, but the 75 I have now takes a lot of cranking. I did a rebuild on the carb, and two attempts at sealing the plugs, with no effect. So maybe I should be looking at running temp more and trying to get that down.

[TJ Hopland]

Its your 75 carb the one with the 6 jets?   Those are supposedly extra prone to issues and were only used part of the year on some models.   I don't think that would have much to do with the boiling so its mostly a curiosity question.  My all stock 75 with that carb would get almost 20 mpg which seemed crazy, the 73 won't do that going down hill. 

At 14-16 psi a 50/50 mix should not boil till the 260-275 range so if everything is good and running in the 200-220 range you got another 40 degrees to go with 'heat soak' when you shut down before you should be boiling.   The mix effects the boiling point but not as much as the pressure does.  Obviously at 0 pressure you are going to be in the 212 range which gives you pretty much no headroom since the minimum temp is going to be around 200.  It could be as simple as a bad cap or corrosion at the filler neck so a new cap is the easiest thing to try.  If the cap is bad be ready to find other leaks when it finally builds full pressure.  When checking and replacing hoses don't forget about the shot piece on the back passenger side head that goes from the head to the water control valve.  It often gets missed because on the RWD cars its totally hidden and hard to access.  The Eldo's its a little better because the engine sits higher and more forward.

The fuel boiling is a combination of today's typical fuels and age just pushing underhood temps up a couple degrees.   When these cars were new they were probably not too far from having the issue so it didn't take much of a change to push things over the edge.  Best thing you can do is everything you can to lower under hood temps.  Make sure your radiator is clean and in good working order.  Make sure you fan clutch is working if you have one.  Make sure you don't have a stuck heat riser valve or other exhaust restriction.   

I had found on mine if I used non ethanol fuel it didn't do it unless it was really hot out.   Also found if I just popped the hood enough to clear the second catch when I parked it didn't usually do it.   That let enough enough air escape to keep the temps down.   Finding non ethanol fuel became a challenge so I got the idea of an electric fan in front of the radiator hooked to a mechanical bathroom fan timer.   When I parked hot I just gave it 5-10 mins and that was enough to keep the temps down.    Worked great for over 10 years of driving.  Went EFI so no longer a problem.   

[Jeff Rosansky CLC #28373]

Mine boiled like a tea kettle just backing out of the garage (ok, not quite). Replaced the cap and all is well.
Jeff