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My Overheating problem...


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Down a qt of coolant is not a good sign, BUT it could be from clearing the heater core IF it was air bound. About the only thing that could have blocked the core was air or sealant tab residue. If it was the latter it will just get circulated and the water pump impeller will take care of it.

Might there be an issue with how the coolant is added back to the system after a flush, that leads to an air lock in the hoses feeding and exiting the heater?

No, there is only one way to add coolant and as long as the purge line is clear it will purge itself.

If there was something blocking the exit hose from the heater at the "T" below the surge tank, wouldn't you at least have heat from the coolant just sitting there in the core?

Yes, but only until that coolant in the core cools off. It must have flow (a constant supply of hot coolant).

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Not impressed with the high running temperature of the 94 STS I just purchased. I noticed the high temp as I blew the rad hose not once but twice. Okay when on the highway but when stopped in traffic it would clime beyond 230 and although it seemed to be a normal thing??? Also normal was blown head gaskets. Thinking that the hot running could be a contributor to the loss of head gaskets, oil cooler seals, etc. Decided to see if I could reduce the running temperature the backyard way. As the fans seem to turn on at much too high of a temperature, I decided to run one of the fans all the time. I took a relay and the fan connector from another Cadillac and wired the fan in front of of the motor to run when the ignition is on. Now the highest its climbed to is 212. Something else I noticed by doing this, the pump is a slacker when idling. When idling the temp rises, soon as the engine is revved up, the temp goes down. Anyway this worked very well for my issue and hopefully will postpone a head gasket failure "forever would be nice".

Love this car.

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Not impressed with the high running temperature of the 94 STS I just purchased. I noticed the high temp as I blew the rad hose not once but twice. Okay when on the highway but when stopped in traffic it would clime beyond 230 and although it seemed to be a normal thing??? Also normal was blown head gaskets. Thinking that the hot running could be a contributor to the loss of head gaskets, oil cooler seals, etc. Decided to see if I could reduce the running temperature the backyard way. As the fans seem to turn on at much too high of a temperature, I decided to run one of the fans all the time. I took a relay and the fan connector from another Cadillac and wired the fan in front of of the motor to run when the ignition is on. Now the highest its climbed to is 212. Something else I noticed by doing this, the pump is a slacker when idling. When idling the temp rises, soon as the engine is revved up, the temp goes down. Anyway this worked very well for my issue and hopefully will postpone a head gasket failure "forever would be nice".

Love this car.

This is your second post. There is so much wrong in this post.

WHO SAID GOING TO BEYOND 230 IN TRAFFIC IS NORMAL? I have seen 235 in AUGUST, IN TRAFFIC, and after a LONG RUN. BUT, 235 is NOT normal as a daily temp, not at all, occasional with a good cooling system only.

Secondly, overheating does not cause blown head gaskets,

If the head gaskets are breached, you do not fix them by revving the engine or hot wiring the fans

The pump does pump less at idle that is no secret.

If your cooling system is not working properly, ie holding pressure, flowing correct, purging air, you will run hotter, untill you renovate your cooling system

Fix your cooling system, that is your problem, pressure test it, check the cap, check for it purging air, check the radiator for flowing, check the thermostat, etc. Blowing the radiator hose off twice does not make sense, something is wrong

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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It does not indicate a block at the water pump, it indicates a block at the "bolt with a hole in it"

Trace the purge line across to the engine, and it will end up around the throttle body, remove the hose from that nipple at the "bolt with a hole in it" and use a 15 mm wrench to remove the "bolt with a hold in it" and clear it out with a drill bit or something.

DO NOT, I repeat DO NOT, blow air through the purge line from the coolant tank to clear it, you will only temporarily dislodge it. The clog MUST be removed by hand

Here is a photo of the bolt with a hole in it from a 96, this hole MUST be clear to allow air out of the system or the engine will overheat, as you will not be able to get enough coolant in and the water pump will cavitate....

Boltwithaholeinit.jpg

Thanks for your input.

I found the connection you have pictured, but now I need to ask a few stupid "I'm not a mechanic" questions:

Is that a re-usable hose clamp that's on there? Looks like it requires a special tool to tighten or loosen.

Your clamp may or may not be like that. Kinda depends on if it has ever been removed before.

If you do not have the special "Hose Clamp Pliers".. you may be able to get it with a small pair of Channel Lock pliers.

If I destroy it taking it off, can I use a screw hose clamp to replace it?

Yes...

The "bolt with a hole in it" will come off counter-clockwise?

Yes...

I know, dumb questions, but I've never done much mechanically on any car, other than add fluids or change windshield wipers! I think I can handle this with a little more direction.

Thanks, John

is the connection in the pic u put on here, also the same in a 98 4.6 northstar?

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Not 100% sure, have a look it will look pretty much the same and it should be located near the throttle body

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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