1993 Cadillac Eldorado ETC (4.6L Northstar V8 - VIN 9)

I have a demon in my cooling system. I bought this car from a man who claimed that the vehicle had a blown head gasket.
The car drives just fine, no smoke, no rough running...but I do have an antifreeze leak.
I can smell it in the engine compartment, but not in the exhaust.
This morning, the coolant temperature shot up to over 255 degrees Farenheit and subsequently switched to "Limp Home Mode"
I felt that the leak could be in the heater core, dropping all my coolant and then overheating the engine, so today I bypassed the core.
Coolant Temp. is fine until hitting heavy traffic and I noticed that the fans may not be switching on.
Anyone know what's going on? Is it a bad sending unit? Is the sending unit in the heater box somewhere? Bad fan clutch? Who else has had this problem?

 

well judging by the year, that thing should have over 100k miles. that is a small project. the correct thing to do is check the cooling system completely, but do to the high milage, you might as well start replacing all the worn parts. turn on your ac, if the fans come on then there is a problem with the cooling fan circuit. ionly things that could be at fault: (from lesser to greater) temp sensor, or related wiring. cooling fan motors, or related wiring, fan control module (4 relays found in the underhood block) or related wiring. PCM or related wiring. those things work with four relyas wired in series. this allows the fans to work at different speeds.

if you smell coolant there is a leak. the northstar has a couple of hidden hoses about 2 inches in length found around the egr valve. they are the hd green type hose used on police cars. you have to remove the tb assembly to replace them. they also have a couple or 3/8's hoses that feed the throttle body, the upper and lower hose, the heater hoses by the coolant tank, a 5/8's pipe that runs behind the rear valve cover, and a 3/8's pipe that feeds the throttle body from the coolant tank. check all these things. it becomes easier to access the rear valve cover by loosening the front two cradle bolts and lowering the front slightly. also check for any contamination, some people only run straight water which corrodes and clogs up the system, also the water pump on the right side leaks from the o-ring.

the water pump could be bad, or it's belt. it's a small project, but it's very important to the northstar. if you overheat u run the risk of blowing a headgasket(s) cracking a head, or worse warping the block (throw away)

 

Okay, took it to the dealer and they replaced my PCM (unrelated to the cooling issues), water pump, and thermostat. Said it overheated no longer and that they saw no leaks. They tested the block before and after the service and said that it was fine.
It's been five days now since I picked it up. Last night, the "CHECK COOLANT LEVEL" light came on.
The coolant temperature has shot up to 230 and 243 degrees a few times since I got the car back, but it always manages to find its way back down. I figured that there were air bubbles in the system that still needed to be worked out. I think I was wrong. this happens more often in traffic, however, it also occurs if I get on the throttle, to.
This morning I let the car idle and brought the engine speed up to 3000rpm to help the temperature rise and I noticed that the fans still wouldn't engage at 225 degrees. I turned on the AC and the temperature went up to 243 degrees before stablizing at 216 or so.

Now you say there are four fan relays wired in sequence under the hood. How do I find out if they are part of the problem?

 

Nice forum if you would like information on any ofthe cars and troubleshooting, fixits or owners and service manuals on CD like the professional use and what you get with a new car, you can click the link underneath. Leroy

 

interesting post since my wife just bought a 1990 ElD from a friend, it does a similiar thing but I noticed the overflow is missing. Have you looked at the radiator cap? if the pressure on the cap spring has changed at all the water will not cycle back and forth between the tank and radiator, also you dont say whether the main fan turns on High speed when the car reaches 240.

You could also have a 180 degree thermo installed to start full flow earlier.

 

bottom rad hoses collapse at high flow, air in the system creates pump cavitation,
Dex-Cool gels blocks passages, hot exhaust leaking into cooling system boils coolant,
stuck thermostats stop flow, backwards thermostats prevent flow, and the best ?
water pump impelelrs installed BACKWARDS dont pump well - yes, the assy people do screw up.

have you tried block & check?

https://www.cadillacforum.com/m_7193/tm.htm

 

I am new to this site and as of yet have not figured out how to post a thread. So I am relying to this one. I just purchased a 93 Allante and would like to change the coolant as a as preventive maintenance. Should it be flushed, or drained? If it should be flushed how is that performed? Does it need the GM tablets crushed up and added with the new coolant? Is there any kind of coolant that I should use? One more thing how do I post a thread on this site? Thanks!