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1997 Cadillac STS
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23 Posts
Discussion Starter #1
i know this prolly gets old telling people the same thing over and over again but i havnt yet found the problem when i searched... any way 97 STS its overheating i have installed a new radiator, new thermostat, new water pump, i can drive for about 20 min and then the level starts to rise and gets to the point where it says to shut down the engine. Sometimes it will go back down to normal and others it doesnt. The block doesnt feel real hot like it should if the temp was reading right....any way after it does this spell it shoots coolant out the overflow tank with alot of pressure and then wants me to fill it up. The tank is holding pressure and shoots out with good force if u open it up. It comes in spurts one day i can drive it and not over heat like a couple days ago it was almost 100 outside and it didnt. but then on other days it just decides f*ck u i am overheating today haha...i am about to go purge the lines and see what happens but any help will be greatly appreciated!
thanks again
Jason
 

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94 ETC,97 STS
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3,531 Posts
Check that the purge line, from the water pump side to the surge tank, is flowing at idle.

Then do the tests Ranger and Krashed suggested.
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #5
Hey guys thanks for all the help. i did the purge test and it is flowing at idle. and its a new cap as well...when it does overeheat thats where the coolant is going is out the overflow it builds up too much pressure and shoots it out the little hose off the resivoir tank. i guess i need to get the cooltant tested...yikes...haha i am not looking forward to a head gasket install!
again thanks and any other tips or sugestions is appreciated!
Jason
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
I once had a hose on my 94 develop a tiny pinprick hole that was not noticeable at all. I stumbled upon it by accident while looking for the cause of an overheating issue that was very similar to yours. And like yours it seemed intermittent... I took 80 mile trips with it and wouldn't have a problem. Then go 15 miles somewhere else and have to stop on the side of the road.


I noticed the temp gauge would do cycles. it would go up to 207 then down to 195 then back up to 214 then down to 200 then up to 225 and back down to 210. Then it would shoot way up over 230 and keep going up untill it overheats.
What I found was the cycles were pretty much like the system breathing in and out. The temp would raise and so would the pressure but the small leak was releasing pressure by letting coolant out. Then enough pressure would be release for the temp to drop. When the temp dropped, the leak reversed and the hole in the hose was sucking air into the system. Then it would start to get hot again and repeat the process. Then when it actually does overheat, the pressure inside is too much for even the cap to handle and so it starts acting like a boiling tea-pot. Once I replaced that hose, all was well.
 

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94 ETC,97 STS
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3,531 Posts
The worst part of overheating on N*'s is so many things give the same symptoms, and they run well except for the overheating!

The exhaust gas test pins it down pretty fast. Just make sure you've driven it awhile with the antifreeze before the test. If you take it in with fresh antifreeze in the surge tank you get a false negative.
 

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1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
Don't waste your money replacing anymore parts, it definetly sounds like a headgasket. Get the coolant tested for exhaust gases.
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #10
hey man you guys rock its nice to hear help from people who actually know something ahaha just off hand does anyone know how much a head gasket install is? I know if i was really serious about it theres a place around here that will install a brand new N* for 6999$ and that may be the best option cus its got 150xxx on it but other tahn that there is no problems the tranny is still perfect... and i love my caddy too much to sell it...any way thanks again guys!
Jason
 

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1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
Its a pretty involved repair, motor and subframe get dropped out the bottom of the car. The headbolts need to be retapped with timeserts as well. Usually anywhere from 2500-3500 dollars.
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #12
i crawled under the car after filling the coolant and letting it sit at a 45 degree incline for about 5 hours and then i noticed a wet spot on the concret coming from somewhere between the oil pan and the transmission so i jacked it up but i really couldnt see anything from the underneath side. i really dont know i got a good mechanic gonna look at it on wednesday so we will just have to see i gues haha cross yor fingers for me!
Jason
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
There are two metal coolant pipes that run around the backside of the engine. They are prone to rust if the paint chips (it did so on mine). usually when they leak it comes out where you described, between the tranny and oil pan. It is an extreme PITA to replace them as they're supposed to come out of the bottom after lowering the cradle a little. Easier said than done. What I did instead of lowering the cradle was I took a hacksaw and cut the pipes in half. Then they were more easily removed. Instead of replacing them with metal pipes I replaced them with heater hose.

You can see them in this pic:
http://www.cadillacforums.com/photopost/showphoto.php/photo/4351/cat/504/ppuser/16457/sl/k

I did have to cut off the "T" from the end of one pipe near the coolant resovoir and leave that on there. After over 5 years of having it like that I've only experienced 1 problem with the setup. The problem was the EGR valve tubing burnt the hose and caused a leak.

You can see how I fixed that here:
http://i29.photobucket.com/albums/c296/Krashed989/100_0904.jpg
http://i29.photobucket.com/albums/c296/Krashed989/100_0905.jpg
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #14
hey thanks man im hopin that thats all my problem is like i said i got a mecahnic gonna look at it on wed. how much of a pain in the ass is it to do what you did with the heater hose?
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
It's actually not that hard to do. Everything can be done from the top. Just know that if you have the heater hose too long it will arch up too high and probably end up with an air pocket blocking the flow. Too high = above the A/C tubing.
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #16
hey man thanks! ill check it out on wednesday see what he says and then i will post back to tell yall the news haha cross your fingers and thanks guys for all the help...
Jas
 

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1997 Cadillac STS
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23 Posts
Discussion Starter #17
So she went to the shop today and good and bad...not the head gasket but it was the coolant cross over i think is what it is called was leaking so 500$ later i get to drive my car home in good condition tomorow plus i have a new water pump and thermostat that i didnt need but the're there now haha thanks guys i hope all is well for everyone else haha later!
Jas
 

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1997 ETC 2007 CTS
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45 Posts
Check that the purge line, from the water pump side to the surge tank, is flowing at idle.

Then do the tests Ranger and Krashed suggested.
My car is now overheating for no apparent reason. I never had a problem before but since I've changed the water pump it overheats, even at idle. Both fans work, but have noticed that the upper rad hose is cool to touch and the lower hose is hot. As for the surge tank line, when I disconnect it I get no coolant flow until the car starts to overheat and then I get flow out of the surge tank. Is this correct? I'm not sure which way the coolant flows, into or out of the tank.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,984 Posts
The purge line flows into the tank. If there is no flow and the top hose is not hot, you have no flow. Check for a stuck thermostat. Incorrect water pump installation. Belt tensioner problem.
 
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