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98 Eldo overheats at idle


mrgot2hav

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Here's my story...

My 95,000mi Eldorado overheated coming off the x-way and I shut it down at about 253deg. let it cool a few hrs. drove it 2miles home and bearly made it before the idle engine message.

I notice a few days before it happened my temp would rise (228-231deg)on the x-way and also at stop lights. After checking the thermostat, radator and plugs I flushed the system and filled with coolant. I began overheating after idling for about 20mins from a cold start so I burped it a few times and still the same.... overheats with fans on high at idle.

Car got roof damaged in a storm just before this so I had to do something to get it to the bodyshop because the insurance Co. was bugging me to death. So bought the "miracle juice" (K&W Nano head gasket repair) that I swore I'd never use in the pass or would even care to think of just to see if it would get the car to the shop and back. Temp is back to normal 190-202degs.

Anyone here seen the head gasket cause this at idle? I though it was just under power or coolant usage. It doesn't use any coolant at all.

I think I may have to do to whole timesert gasket job when it gets out the shop though I didn't check the purge line for a plug.

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Usually head gasket leakage doesn't manifest itself at idle or light engine load until it gets really bad, and that can be many months after the first symptoms -- coolant usage, then overheating after topping a hill or passing a car on the highway, etc. Overheating at idle strikes me as being something else.

You've already verified that the fans are operating normally. Did you get a Delco thermostat and radiator cap made for your car? Does the cooling system hold pressure overnight? Did you add the pellets to the lower radiator hose when you refilled the cooling system? If so, and if you don't have any codes, the next place to look would be the water pump belt.

My overheating experience (with Northstars) is limited to a head gasket problem last year. Others with cooling system problem experience will have more to add here.

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Check your cap

Pressure test your system for pressure leaks

Check your water pump belt and tensioner

Check the purge line air in the system might cause problems at idle

Check for a air blockage or restriction through the radiator

Check your coolant concentration

Did you change your thermostat?

This does not sound like head gasket problems, you were not loosing coolant

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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Thanks.

Got the car back, and.. they towed it for me overheating at idle again. Spent last nite working in 90degs temps Whew hot out! Fans are working, I didn't check the manual to see when the low fan comes on but I know the high fans comes on when it's not too far pass the middle of the gauge, I forget the exact temp but i'll check after work tonite. High fans stay on and temp never comes down, will overheat if I let it with fans on.

Now here's the dumb mistake I found, I put my press tester on it to see if it would build press right at start up or all of a sudden after a certain temp to kinda see if the cylinder was pressuring the system and it doesnt, but what I did notice is with the tester on it temp stayed at 208... put the a/c low to let it cycle the fans just to see what would happen and it holds at 196degs. hmm now back to what I should have did 1st instead being N* headgasket worried.

Checked the cap and it doesn't hold for even .5 sec leaks right down. Bought the car used my 1st N* it has a normal silver 15psi cap on it. Is that correct? I didn't realized how picky the N* cooling are. Worked as a tech at Ford dealer years ago and never seen a cap cause overheating though I know higher press give you a higher boiling temp, but that was before modular engines lol.

All I had at time time was green antifreeze so I used that because I figured it would be getting flushed out later anyway, ran out of time but today i'll...

Buy cap, dexcool, pallets and thermostat too be safe.

Let it idle with the a/c on and check the low fan on temp. Have to find specs.

I'll report the findings.

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Sounds like you found the culprit. I believe a 15# cap is correct. Our old Guru (GM powertrain engineer) always told us that once you go green, you have to stick with 2 yr coolant changes. I have heard others say that is not true. That said, (before I knew better) I once put green in my wifes '96 Bonneville. It was only in for a day before I switched back to Dex. I asked him if I was OK with that and he said it was not in long enough. Not sure what to think, but I have had no problems. Just to be on the safe side, I'd flush it ASAP.

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I wouldn't label the engine as picky - you had a defective component (the cap) and the cooling system could not build pressure. I'd get that green coolant out of there asap! Drain it and measure the amount drained so you know how much water will be left in the system after flushing. That way, you can get the DexCool coolant concentration as close to 50/50 as possible.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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No the NS isn't picky, this is SCIENCE at work here. Water/coolant under pressure boils at a higher temp than water/coolant not under pressure. Loose coolant and temp goes up, the reason you had a problem at idle is because your coolant was LOW and the pump probably cavitated at low RPM or the coolant boiled due to the reduced air through the radiator

THAT is the reason I said CHECK THE CAP first. darn I'm good :lol: if its fixed, I'll send you the address to send money to...I'll take 50% of what the dealer would have charged, :lol:

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thanks guys, didn't mean picky in a negative way, I love the car and powertrain. Being the 2nd owner I really don't know the coolant history so i'll be changing the dex-cool often anyway. I dont have the manual with me at work but I kinda remember, a TSB or something saying if you have green in the system go with a 60/40 mix and change it soon (I forget how soon). It talked about the corrosion inhibitors get neutralized or somethingwhen green is put in. Anyway to be safe it will be changed often in the future.

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Thanks guys, didn't mean picky in a negative way, I love the car and powertrain. Being the 2nd owner I really don't know the coolant history so i'll be changing the dex-cool often anyway. I dont have the manual with me at work but I kinda remember, a TSB or something saying if you have green in the system go with a 60/40 mix and change it soon (I forget how soon). It talked about the corrosion inhibitors get neutralized or somethingwhen green is put in. Anyway to be safe it will be changed often in the future.

Dexcool should be used with a 50/50 concentration unless you live in an unusually coold climate. If you measure the amount of coolant drained from the radiator, you will know how much coolant to use and the amount of extra water to add. Mix the Dexcool with water (preferrably distilled) prior to adding it to the system. After you drive the car for a few days, use a coolant tester (or better yer, a coolant refractometer) to verify the coolant is at 50% concentration. Adjust as necessary. If you use one of the Prestone testers, verify the tester with a 50/50 dexcool water mix - it should read -34 degrees. If not, note the position of the needle when you test your car's coolant.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Found out that my low fans don't come on, the high works right to the specs. Manual says low fans ON@223degs / OFF@217degs. High fan ON@234degs / OFF@223degs. Because of the NBA game didn't get my meter out to check fuses or voltages. Will look for DTCs 1st I'm thinking this should flag a code. Even after running high it doesn't drop down to low instead the fans just turn off at 223degs.

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It was the fan relay #2. Took the relay apart the normally closed contacts was pitted abit causing low fan to work erratic. WHEW!!! cheap fix, overheating solved by rad. cap and fan relay. By the way the relay set no DTCs, I thought it should but maybe it was because it had a "low" voltage connection thru the bad contacts.

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