A friend has run across a cosmetically excellent 50,000 mile 85 Eldo Conv. It starts and runs great and everything works but after 10-15 minutes of running it begins to overheat. I am 1000 miles from the car so I cant put hands on it and was wondering if this is a common problem or if it means a shot 4100. Both oil and coolant appear free of each other and I was wondering if could be as simple as a thermostat, water pump or clogged radiator or if this is an early sign of catastrophic failure in a 4100?
Ummmmmmmmm........ I think you know the answer, but it could be a simple fix.
Time for some coolant checks.
Bruce. >:D
Bruce is as usual, is on target, yes the 4100 was a " torture chamber" but overheating was not high on the list, all the things mentioned are average issues with any older car , 25 years could produce anything. Head gaskets were not common.
The oil and coolant mix I think came from an intake gasket issue. With age and low mileage I would be concerned with a major sludge build up in the cooling system from regular age and the over use of the special pellets. Problem with ANY aluminum engine is when you get em good and warm you end up with head gasket issues. When you had all cast iron they could take it for a while, start mixing em or all aluminum and you got problems. Every head gasket issue I ever heard of was 'it overheated a few times' or 'the light came on but I made it home'. A common way to test for a head gasket problem is to take to a shop that has a exhaust sniffer and instead of sticking it in the exhaust pipe they put it to the radiator cap, if it 'smells' exhaust you got a head gasket problem. If its bad enough a cooling system pressure test will show it also but at first the minor leaks start by leaking exhaust into the cooling system rather than coolant into the cylinders. The reason it overheats from that is the air bubbles get into the water pump stall the flow or get around the T stat and dont allow it to open, either one of those issues causes lots of hot spots which causes more boiling and bubbles. If you are lucky the radiator cap will push it into the overflow, not lucky it will blow the radiator or hoses.
Jim,
I wouldn't start and guess at the most catastrophic possibilities, if this was my car I would start with a check of the pressure cap, followed by an inspection of the hoses to make sure they were not collapsing, followed by having the radiator flushed out.
You did not say whether the car was loosing coolant or whether the overheating was while in traffic or on the road.
Air across the radiator is a necessity and checking the fans, fan motors and radiator fins for debris would be next.
After I had done all the above I would begin to look deeper.
Greg
Question: Do you have heat from the heater core? One of the service issues with that vintage of Eldorado had to do with the service fill of coolant. The heater core was high and to the rear and fed from a small hose at the back of the block (strange little pre-formed hose). After filling coolant, the engine has to be rev'd up to at least 2500 to 3000 rpm for a minute or more with the radiator cap off for the waterpump to get enough pressure to purge through heater the core. Sometimes it takes several purge cycles to get enough coolant into the system. Filling with out doing the purge can leave air pockets in the cooling system that can give the engine overheat condition. Cadillacs have two different "hot" sensors one is coolant temperature, the other is metal temperature. If the coolant level is not totally purged that sensor will not register coolant temp correctly as it actually is measuring "air" temperature in a pocket, it is only after running for a while with the low coolant that the metal temp sensor finally comes on.
Last time I had the system open on my 80 after doing the traditional warm up with cap off and topping off the radiator off each of the next 3 mornings the overflow bottle was empty and needed to be refilled. After those 3 times its stable. I have flushed the thing 3 times now and I still get brown slime floating on top of the coolant. Other than age the water pump and radiator looked fairly new when I bought it so I suspect that at some point in the last 30 years someone dumped a lot of stop leak in it.
Why hasn't someone already checked the thermostat, water pump or if it's a clog radiator? Before you jump the gun checked these basic areas out FIRST of course. EAM
About the sealer, all those HT engines had the "horse pellets" from day one and they need to be put back in after coolant flushes, this was to help seal the cylinder sleeves.