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1999 Cadillac Deville tons of overheating issues.


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So my Cadillac overheats all of the time for so many reasons. As I'm sure the people who will reply will know, GM used to recommend adding tablets of stopleak into the coolant system in every change. A while back when I had NO idea what I was doing I also added a whole quart of the stuff to my coolant system. Needless to say my system is clogging up everywhere. I flushed the larger part of the system with what I could get at with a garden hose and the upper/lower radiator hoses. I assume there's still some in the heater core and that area that keeps clogging up the smaller tubes including my purge line that I have unclogged twice. My AC/heat system also doesn't work and the fan in my cab does not turn on, when I put it to hi or anything. The AC will turn on (I mean it doesn't do anything because the fan won't turn on, if you could comment on that issue if it's separate or whatever that'd be great too) but it turns off instantly because it's low on refrig. I assume there's probably an issue somewhere so I haven't put any more refrigerant in because there's probably a leak... that being said, when I turn my car on there is a loud squealing sound coming from where my serpentine belt is and I'm going to go out on a whim here and say that's my AC pump? is it completely out? Earlier today my lower radiator hose detached itself... probably from too much pressure or something? I also noticed there is no coil in it... I had replaced that hose a while back, was it supposed to have a coil in it? is it collapsing?
Another thing people keep telling me to do is a block test just to get that out of the way... I'll probably do it eventually but right now... meh... This is my baby. I'm 19 years old and I earned every penny put into this car in acquiring it and fixing it from the ground up and it'd be a terrible shame to have a blown headgasket so I'm trying not to consider that. There is no oil in the antifreeze and no antifreeze in the oil, but I've also been told they do not fail in this way. I also like to think because of the countless other issues it has that it is those that need to be fixed rather than a head gasket.

Anyway... Hope to hear back soon. Cheers!

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If you addtd that much sealant to the system through the surge tank, it may have plugged up the purge line - especially if you added it to the surge tank. The sealant should be added to the lower radiator hose. Also, I believe the hose should have the spring in it to keep it from collapsing. Typically, the spring needs to be transferred to the new hose. In order to get the excess sealant out of the surge tank, you will need to disconnect the hoses and flush it with a garden hose.

Disconnect the purge line at the surge tank - it is the small hose that is near the neck (not the overflow hose). It runs from the surge tank to the throttle body area on the driver's side of the engine. Have someone start the engine. There should be coolant flowing out of the hose. If not, the purge line is plugged and that is the cause of the overheating. You will then need to trace the purge line to where it connects to the water pump crossover and remove the hollow bolt/connecter and clean it.

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

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Mechanic in a can is just another way to shoot yourself in the foot. If you have questions, this is the place to ask.

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Everything you say tells us that a clogged cooling system is your problem. Anyone that is talking blown head gasket is talking about their own head, not your car. But to be absolutely sure for very little time and money, get the coolant tested for combustion products.

Your nose can tell you almost as well as the test kits. If the surge tank smells of exhaust, or if the exhaust smells of coolant, then you have head leakage. The best time to check the exhaust is in the morning; start a cold engine, let it idle for just a few seconds, shut it down and go to the back of the car. If it doesn't smell of coolant, you are likely OK for head leakage. If the cooling system holds pressure, you can check the smell of the surge tank anytime, including in the morning when the engine is cold.

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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I had previously flushed out my cooling system like you had said to. This was about a month ago. My purge line was also clogged, I blew it out with an air compressor. It ran fine for maybe 2 weeks, tt thehen it started overheating again. I flushed the system again, and blew out the purge line, and it ran fine for another week. Now the purge line was clogged again yesterday. So it seems like perhaps there is extra stop leak somewhere in the system that the water from the garden hose just can't get to. So... Perhaps the heater core? What are your thoughts? How exactly do I fix this?

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I had previously flushed out my cooling system like you had said to. This was about a month ago. My purge line was also clogged, I blew it out with an air compressor. It ran fine for maybe 2 weeks, tt thehen it started overheating again. I flushed the system again, and blew out the purge line, and it ran fine for another week. Now the purge line was clogged again yesterday. So it seems like perhaps there is extra stop leak somewhere in the system that the water from the garden hose just can't get to. So... Perhaps the heater core? What are your thoughts? How exactly do I fix this?

If it run fine every time you clear the purge line, everything else is probably OK.

You are going to have to flush the system good enough to get all the stop leak out so the purge line will flow properly.

Anytime the purge line stops up... it WILL overheat.

repeated overheating is very bad... you don't want to be continually overheating it.

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How do I flush it good enough though? I had flushed it twice, one time I had the hose running in it for 40 minutes. It seems as though there's spots it just doesn't have enough pressure to get to or something, where would these be and how specifically do I get to them?
I have not done a block test, but I guess eventually I will when I get around to buying the kit.

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You need to remove the hollow bolt where the purge line connects to the water pump crossover and clean it out. By blowing into the hose with a compressor, you're just pushing the clog back into the cooling system. The car will run OK for awhile until the crud finds its way back into the purge line, then it starts overheating again.

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

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How do I flush it good enough though? I had flushed it twice, one time I had the hose running in it for 40 minutes. It seems as though there's spots it just doesn't have enough pressure to get to or something, where would these be and how specifically do I get to them?

I have not done a block test, but I guess eventually I will when I get around to buying the kit.

I would have a professional radiator shop flush the system. A good one will use special equipment, pressure back-flush of the radiator, block, and heater core, and special solutions, and flush those out before replacing your coolant - and the right amount of sealant. Also, if there are any small leaks, they will either call you about them or, if they are things like seepage at the radiator hose clamps, just fix them. When you are done, you will have a clean cooling system, 50-50 antifreeze coolant, and the right amount of sealant.

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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Im afraid that you may need to get this done professionally. I am always reluctant to take my stuff to someone to have it "professionally" done - but in this case even i would. That stop leak turns into a rubbery substance that can easily dislodge, and clog your purge line over and over. It'll never end, and you will overheat, and warp your heads. Don't be penny wise and dollar foolish.

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