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Okay so i've had this deville for a little over 2 years, I purchased it driving an non over heating. A week later i took it on an hour long trip an started over heating. Every since then I have took it to 2 shops one had told me it was a cracked headgasket the other said it was a hole in the radiator changed the radiator an still comtinues to over heat. It was driven everyday for 6 months to an from work 20 mins still overheating. Keep in mind i was told it had a bad headgasket an still a 2 years after driving i have no signs of bad headgasket. No oil an anitfreeze mix. No smoke out the tailpipe. My dad has put a $100 "liquid fix" in it which i heard was not good to do. But im really stumped. Could the internal water ports be clogged ? Need help!!

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:welcomesmiley:

There are a lot of things that can make a car overheat. Changing parts without a diagnosis is... not thoughtful.

You can diagnose, or rule out, head leakage by having your coolant tested for combustion by-products. Since your car has been overheating for some time, you can probably get a good idea yourself. With a cold engine, first thing in the morning, open the radiator cap and sniff the overflow tank. If there is no exhaust-like smell, that's a very good sign. Then start it, let it run for about 30 seconds, then shut it down and go to the rear of the car and see if the exhaust smells of coolant. If it does not, then you are unlikely to have head leakage. To make absolutely sure, have the coolant tested - but make sure that the coolant has not been changed or flushed in at least a week to make sure that the test works.

Radiator fans that don't work will cause overheating in a stationary or slowly moving car. When the A/C is ON, both fans should run in low speed. If not, make sure you can turn both fans easily when the engine is off and cold, and check the fuses. Then get back with us for help in finding electrical problems with the fans.

A common cause of overheating is a clogged bypass hose. This hose goes from the thermostat area to the surge tank. With a cold engine, pull the hose off the surge tank and start the engine while looking at the hose; it should run freely at engine idle. If not, check the fitting at the thermostat end, the "bolt with a hole" first.

Those three things will rule out - or diagnose - head leakage and the most common causes of overheating in Northstars. Get back with us after you look at these things and we will help you fix your car.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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The 2 biggest questions I ask.

Does it have a cold start misfire if it is parked overnight, over the weekend, or over a period of a few days or so?

Does it use coolant?

Welcome to Caddyinfo.

Note A minor HG problem will easily pass the by products test.

Also when you say overheating how hot does it get? (idle engine message, change engine oil, engine overheated, ac off for engine protection, etc...)

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Check the purge line. I had one that was rusted and so clogged with the mechanic-in-a-can that i have to remove the purge line and install 3/8 tranny hose in place of it.

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  • 4 weeks later...

The 2 biggest questions I ask.

Does it have a cold start misfire if it is parked overnight, over the weekend, or over a period of a few days or so?

Does it use coolant?

Welcome to Caddyinfo.

Note A minor HG problem will easily pass the by products test.

Also when you say overheating how hot does it get? (idle engine message, change engine oil, engine overheated, ac off for engine protection, etc...)

The 2 biggest questions I ask.

Does it have a cold start misfire if it is parked overnight, over the weekend, or over a period of a few days or so?

Does it use coolant?

Welcome to Caddyinfo.

Note A minor HG problem will easily pass the by products test.

Also when you say overheating how hot does it get? (idle engine message, change engine oil, engine overheated, ac off for engine protection, etc...)

yes it uses coolant. And yes it had a misfire, but not only on cold start etc. Its only at idle but once you drive it drives smooth as can be. An it gets so hot it say its going to shutdown. But it never has.
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Check the purge line. I had one that was rusted and so clogged with the mechanic-in-a-can that i have to remove the purge line and install 3/8 tranny hose in place of it.

purge line doesnt seem to be the problem, ive cleaned it with weed eater wire before an it was not clogged.
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Pressure test the radiator/surge tank cap. It should hold 15-16 psi if not replace it...

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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So it does have a cold start misfire then?

It clears up as it is driven.

If you try supplement tabs and it cures the misfire for awhile you have a HG leak.

What happens is the coolant will leak into a cylinder and when the car is started next it has to burn off the coolant (does not ignite)

Just throwing that out there.

It is right to the point from what you have posted

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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With a cold car in the morning, start it up for a few seconds, then shut it off and walk around and smell the exhaust. If the exhaust smells like coolant, it has head leakage. Then carefully take off the surge tank cap and smell the surge tank. If the surge tank smells like exhaust, you have head leakage.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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