1967 Overheating Issue

[dn010]

James - you note that the radiator has been flushed and pressure tested, but what about the entire system (engine, heater core, etc.), have those been flushed as well? Do you recall what color the fluid was when flushed?

[cadillacmike68]

Isn't there supposed to be a cover over the radiator top??

Have you tried running it with the cap OFF to observe when the t-stat opens and the coolant starts to flow?

You should see it coming across top top few tubes and running down into the bottom of the return tank as soon as it gets up to  operating temp. If the level starts rising up on you too fast (a sure sign of overheating somewhere in the engine), just shut it off and cap it.

Get a digital thermo gun and check the temp of the the block where the upper hose comes out of the block, where the upper hose goes into the diver side radiator tank and where the coolant is on the passenger side tank. The first two should be very close or the same. The right side should be 15-25 degrees cooler, once it is up to temp.

[Snibbor]

Thanx Mike. Will do. Would having a 170 vs. a 190 Thermostat be a source of the overheating issue? And if so I assume the 190 would be the ONLY one to have...Anyone know the answer on the Thermostat?

[dn010]

I believe the standard temp thermostat for that engine was 180. You won't overheat by using a 190. You can get thermostats between 160-205 degrees for that engine, none will cause it to overheat - they will just allow the engine to begin cooling at lower or higher temp depending on what you want. Now if the thermostat is defective and doesn't want to open at all or partially, that is another story.

[Snibbor]

Thanks DN. I had a 180 installed and it is in good working order. Still have the gradual temp rising issue though. Gonna get a compression test later this week. Lord this issue has been perplexing.

[Jeff Rosansky CLC #28373]

We just did the water pump on our 55. When I had it all apart, I went ahead and verified the thermostat's operation. Just stuck it in my wife's favorite saucepan and a candy thermometer. Started opening 180 and fully open just over 200. Just like the specs say.
Maybe you could just remove the thermostat and see if your problem persists. That would eliminate the thermostat question altogether.
Jeff R

[Snibbor]

I might try that. Has anyone heard of "rodding out" the radiator?

[V63]

A problem cylinder taking water will have a steam cleaned spark plug. Maybe check your spark plugs?

If a head removal is eminent... A cracked head is more 'probable'. Be sure to get the heads tested before reassembly.

Ridding a radiator is the process of removing the end tank and running a rod thru each tube to clean out deposits.

[dn010]

For whatever reason, the jury still seems to be out whether the entire cooling system was cleaned/flushed and pressure tested, or if it is just the radiator that was flushed and tested. With all the replacement parts and checks thus far, my money is still on buildup of sludge around the cylinders in the water jacket, especially if your fluid is going in green and coming out brownish looking.

[Snibbor]

Compression test will rule in/out head gasket correct? Then I'll go back and do the coolant reflux again (assuming they were deficient on the first coolant flush)....

[Jeff Rosansky CLC #28373]

especially if your fluid is going in green and coming out brownish looking.

I flushed the crap out of ours. On the 79, I drained and filled until it was clear. Then filled it with water, drove it to get it hot, and then drained again. Did that 9x until the water was clear.
Did the same on our 55 when we got it 5 years ago. Just did the water pump a few weeks ago and had to heavily flush it again.
So I would say if you are still getting brown out of it, then there is still gunk in there.
Jeff R

[Snibbor]

Ok it seems the temp gauge stays at about 1/2way (shortly above.I know these dash gauges are inexact at best but will be adding one under the hood soon) on small drives but inches up and up at idle when parked. I have to wait to take her into the only real Cadillac repair shop here in my metro...gotta wait until 07-27. Worth the wait to get this finally resolved.

[The Tassie Devil(le)]

Engines were never designed to be idled for extended periods.

You have to remember that the critical part of the oiling system is lubricating the Cam Lobes and Lifter Bases.   This is accomplished by oil being thrown at the underside of them by crankshaft rotation, with the outflow of oil from the big ends being thrown around the crankcase, and striking the lobes and lifters.   There is no oil galleries to perform this function.

Plus, the cylinder bores, that is the area under the piston is sprayed by oil from the opposite big end, squirting out to the side and up under the Piston to lubricate the Gudgeon Pins.

Oil is not just for lubrication, but also cooling as well.

An idling engine suffers from decreased air flow through the radiator, and one of the reasons why engineers build idle "increases" for want of another term, when the AC is on.   Raising engine speed assists in cooling.

Plus, idling with the hood open allows the air that is supposed to be flowing through the radiator, to come in the easy way, from the sides, avoiding the constrictions of the Radiator and AC Condenser.

Bruce.

[Snibbor]

Thanks Bruce,

One more important question. If the car temp cools down (whenever I go at speeds in excess of 25-30mph) does this discount a blown head gasket (as the temp would rise REGARDLESS if it were a blown head gasket)?

I just cannot sit a stop light (or group of lights) for any period of time without it inching up (ALBEIT SLOWLY) and up to excessive temps...

[The Tassie Devil(le)]

James,

As has been mentioned before, without knowing what the actual temperature readings are, it is hard to know.

Don't forget that there are many things than can be wrong with a "blown" head gasket.   Where is the compromise?   The head Gasket performs many tasks.   Keeping the coolant separate from the oil.   Keeping the Compression contained within the big ring, and away from the coolant and oil, maintaining the correct distance between the head and the block.

As the engine heats up, everything expands as it gets hotter.   Head Bolts stretch, Heads and blocks expand, and this poor Head Gasket still is expected to seal everything without leaking in any direction.

With your description of temperatures rising when not moving, but cooling down when moving, it really sounds like an air-flow problem, or it could be a coolant flow problem, or even a combination of more things that I cannot think of at the moment.

Driving hard up a hill, the temperatures will rise, because the engine is working hard, then after going over the top, and less pressure on the engine, the temperatures will cool down.   An out-of-tune engine will run hotter due to the fact that it is not performing as it was designed to.

A lean engine will run hotter than a rich engine.

Bruce.

PS.   You really have to get an accurate temperature measuring device to know what the temperatures are. 

[Jeff Rosansky CLC #28373]

Put some monster fans on front of the radiator blowing serious air into the grill and let her idle. See what the temp does with it idling with the air moving then you can rule airflow in/out of the equation.
Jeff R

[Snibbor]

Thanks again for all the input. I'll circle back later this month when the experts finally get a crack at my coolant issue.

[Snibbor]

All,

I finally got my caddy back after 3 weeks. They solved the problem with a new (aluminum) radiator..The diagnosis was that the lower part of the radiator was clogged and generally corroded. It was the original copper radiator. The fan clutch was removed and replaced with a CORRECT (non-Chinese) fan clutch... Alls well that ends well.

Thanks again to Bruce and everyone else's all the input. I love this place. I love my CDV!

[The Tassie Devil(le)]

G'day James,

Congratulations on getting the problem fixed, and thanks for letting us know what the problem was.

Bruce.

[79 Eldorado]

I just started reading through this thread today. Some of the OE service replacements by the end of CuBr production at Harrison Radiator had extremely low gauge air centers. I had a radiator on my daily driver which started causing cooling issues in less than one year but including one WNY salty road season. I had just changed the radiator and so I checked it off as not a possible cause. The car had a completely rebuilt engine within the prior couple of years and all parts including the heater were new parts. Finally I took a close look at the radiator and the entire lower half appeared to be colored differently due to corrosion. I touched some of the fins and they disintegrated with a light touch. The problem started prior to a year aftewr replacing the radiator but because I thought it was inconceivable it could be the radiator it was a few months later when I finally fixed the issue with a new radiator.

A couple of other comments:
-Someone commented on spark plug color to check to see if there were signs indicating a head gasket issue. I thought that was a good idea but I don't think there was a reply to that.
-I never saw a reply to whether or not there should be a "close-out" seal/panel over the heat exchangers. If there should be and it's missing you may have idle air recirculation, meaning hot air may be getting sucked from inside the engine compartment to the entrance side of the radiator.
-I never saw any comment suggesting checking the condenser condition for damage or plugging with debris. Even if the AC is not running the air still needs to get through the condenser. If there is excessive fin damage or there is a lot of debris it can reduce airflow and the added restriction can encourage an recirculation situation.

Scott