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85 Eldo Overheating

Started by okccadman, December 09, 2010, 06:10:28 PM

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okccadman

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?
Jim Jordan CLC# 5374
Oklahoma City, OK

55 Series 62 Sedan
56 Series 62 Coupe
56 Fleetwood 75 Derham Limo
59 Fleetwood Sixty Special
66 Fleetwood Brougham
66 Superior Hearse/Ambulance
67 Fleetwood Sixty Special
68 Fleetwood Eldorado
76 Coupe de Ville d'Elegance
90 Brougham
92 Fleetwood Coupe
93 Allante
94 Fleetwood Brougham
02 Eldorado Commemorative Edition

The Tassie Devil(le)

Ummmmmmmmm........ I think you know the answer, but it could be a simple fix.

Time for some coolant checks.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Dave Shepherd

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.

TJ Hopland

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.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364


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
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Tim Pawl CLC#4383

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.

TJ Hopland

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.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

EAM 17806

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
Ev Marabian

1976 Cadillac Coupe DeVille, 1989 Chevrolet Caprice Classic, 1990 Pontiac Bonneville and 1996 Buick Skylark

Dave Shepherd

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.