99 deville overheating but don't know where to find thermostat

13536 Views 60 Replies 9 Participants Last post by avatrx, Mar 6, 2011

avatrx

Discussion Starter · Jan 18, 2011

our 99 deville overheats and then makes a terrible noise. the part I don't get is when I slow down it COOLS down, but not to an acceptable level.

when it overheats it throws the coolant out the overflow.

my hubby bought a thermostat but can't determine where it goes. the autozone gave him a diagram but apparently it looks nothing like our car.

what is the temp (F) that this car is supposed to be when OK but not too hot?

I drove it last week and it went to 230+. that's when it started making strange noises. I parked it to let it cool and checked the coolant level. It had blown out all the coolant we had put in it before my 40 mile trip. I added more and 'crippled' it home.

can someone help? I get stuck doing this stuff because my hubby isn't computer savvy, but if you could be specific - I can show that to him. I'm not automotive savvy.

currently this is the only mode of transportation we have and everywhere we go is a trip since we live out in the middle of nowhere.

thank you in advance.
-susie

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Ranger

· #2 · Jan 18, 2011

The thermostat is at the engine side of the lower radiator hose, but I doubt that's your problem. Get a block test kit from Napa or rent one from Autozone and test the surge tank for exhaust gases in the coolant.

P.S. You posted in the "Tech Tips" section. I'll move this to the Deville forum for you.

Ranger

· #3 · Jan 18, 2011

The thermostat is at the engine side of the lower radiator hose, but I doubt that's your problem. Get a block test kit from Napa or rent one from Autozone and test the surge tank for exhaust gases in the coolant.

P.S. You posted in the "Tech Tips" section. I'll move this to the Deville forum for you.

avatrx

Discussion Starter · #4 · Jan 18, 2011

Thanks for the info. curious - how would exhaust gases get into the coolant and what might cause that? a block hose or something?

I don't claim to know alot about cars, but I'm always interested in the 'hows' and 'whys' of something. it never hurts to have information..........

I'll pass your suggestion onto the hubby.

again, thank you.
susie

70cougar

· #5 · Jan 18, 2011

avatrx said:
how would exhaust gases get into the coolant and what might cause that? a block hose or something? susie

Some of these cars, including your year, can have the serious problem of pulled heads bolts that cause the head gaskets (HG) to leak. So exhausts gases from the combustion cylinders get into the coolant. Do a search here on HG and overheating & you'll find many threads about it.

But don't drive yourself crazy - do the test that Ranger suggested & let's hope you get lucky and the tests are negative. Fixing HG's is costly.

Submariner409

· #6 · Jan 18, 2011

Unfortunately, the most common cause of exhaust gases getting into the cooling system and causing overpressure is blown head gasket(s). The 99 Northstars are (unofficially) the worst offenders with 97 and 98 a close second. The problem lies in the cylinder block castings - the head bolt hole threads fail, allowing the cylinder head to move, causing the gasket to fail. You would need to study up on "open deck cylinder block" to learn why ANY loss of head bolt clamping pressure will cause damage.

Given your situation and apparent limited Cadillac Northstar repair expertise, my advice is to get the car to a good auto repair shop - fast. IF the cylinder head bolt(s) have failed, you're in for a $2,000+ repair, and it's at least a 3 day job, even for an experienced shop with all the correct tools: the entire drivetrain needs to come out the bottom of the car.

Ranger's coolant test kit checks the air/gas over the coolant in the reservoir for the presence of exhaust gas. It uses a chemical fluid and vacuum to draw an air sample through a test liquid; if the liquid turns from blue to green to yellow, there's exhaust gas in the coolant.

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iametarq

· #7 · Jan 18, 2011

This should help. I took a video of me using a test kit for this same problem. My Deville is currently having that repair done that I shall not mention.

avatrx

Discussion Starter · #8 · Jan 18, 2011

Dear Sir,

Thank you for your help. I just noticed that you are located in Woodstock, IL. You're just down the road from us. We're in Hebron.

My hubby is calling autozone as I write this and checking into the test kit.

Wish us luck. I think I"d find a different car before spending thousands to fix this one. He has some automotive experience but mainly with the older cars that didn't have all the electronics. I guess he would be classified as a 'shade tree' mechanic. Long past his hobby-stock cars that were more fun to work on for the Lake Geneva track. He really hates working on cars at this point.

-susie

avatrx

Discussion Starter · #9 · Jan 18, 2011

if the liquid turns from blue to green to yellow, there's exhaust gas in the coolant.

if that proves to be the case shall we expect that the problem is indeed with the head gaskets?

I hate the thought. Time for a replacement car. Old is fine. I've currently resurrected my 92 lebaron conv with 108,000 miles on it. Never had issues like this with that one.

you folks are really great. I really do appreciate all the help. I just wish it were the hubby doing the communicating. I'll show him the video when he gets back.

susie

Ranger

· #10 · Jan 18, 2011

I just noticed that you are located in Woodstock, IL. You're just down the road from us. We're in Hebron.

Well HI there neighbor. I was just in Hebron last week. Let me know if you need any help.

I guess he would be classified as a 'shade tree' mechanic.

Welcome to the club.

if the liquid turns from blue to green to yellow, there's exhaust gas in the coolant.
if that proves to be the case shall we expect that the problem is indeed with the head gaskets?

Yes.

Good luck and keep us posted.

avatrx

Discussion Starter · #11 · Jan 19, 2011

Thank you so much for your offer. We may just take you up on that.. Bill is miserably frustrated. He's more than willing to work on the car, he just feels like a fish out of water with the electronic stuff and the cadillac.

Not sure the best way to give you a direct contact number here. We have the silkscreen business on 173 just west of town. we're always willing to swap for services

The autozone in Woodstock didn't have the test kit but the one in McHenry does so I'm headed there this morning to get one. $25 and if you return it (which we will) we get 100% refund.

I'll keep you posted..................
-susie

iametarq

· #12 · Jan 19, 2011

Ranger, we need shirts! :histeric:

Submariner409

· #13 · Jan 19, 2011

iametarq said:
Ranger, we need shirts! :histeric:

Tchirts - Gotta have tchirts - car, boat, submarine - gotta have tchirts !!!

Cadillac Forums - How to fix your boyfriend's pump !

Ranger

· #14 · Jan 19, 2011

avatrx said:
Thank you so much for your offer. We may just take you up on that.. Bill is miserably frustrated. He's more than willing to work on the car, he just feels like a fish out of water with the electronic stuff and the cadillac.

Not sure the best way to give you a direct contact number here. We have the silkscreen business on 173 just west of town. we're always willing to swap for services

The autozone in Woodstock didn't have the test kit but the one in McHenry does so I'm headed there this morning to get one. $25 and if you return it (which we will) we get 100% refund.

I'll keep you posted..................
-susie

Best way is with a PM (personal Message). Just click on my name to send one.

avatrx

Discussion Starter · #15 · Jan 19, 2011

iametarq said:
Ranger, we need shirts! :histeric:

Unfortunately we're the silkscreen people that do everything (almost) BUT textiles. We do signs, some vinyl lettering, mostly point of purchase displays - printing legends on manufactured parts etc. BECAUSE we were mostly in the mfg business, (most of that work left the country or just plain went away over the past 10 years) that's why we're forced to work on our own cars.

I picked up the test kit. of course they didn't tell me I needed some type of fluid to put in first. (I hadn't watched the video yet). another 22 miles back to get the fluid but there is another possibility.

Hubby changed out the thermostat. While checking to see if that made a difference he noticed that the cooling fans were not kicking on until over 222 degrees and not necessarily even then.

Now I'm on to another trip to Advance Auto to pick up a cooling fan sensor.

We're not sure how hot this car should run. I'm quite sure the232+ was too hot, but aside from that I don't really know. I do know that when the fans come on, the car almost instantly cools to 206 - 210, but for some reason they don't come on until a higher temp.

My kingdom for a basic straight 6 engine. no electronics. I don't even need fuel injection since I learned how to drive in the late 60's. I had to teach my son how to start his 77 Corvette which we sold him years ago. Fortunately he's an ex 'NUKE" and he catches on quickly................

-susie

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avatrx

Discussion Starter · #16 · Jan 19, 2011

Ranger said:
Best way is with a PM (personal Message). Just click on my name to send one.

Tried that. Since I haven't been on the forum long enough, they won't let me do that.

susie

Submariner409

· #17 · Jan 19, 2011

Susie, The fans are a two-control process. With NO a/c function called for the fans go to SLOW at ~224 and FAST at ~236. The coolant drops to ~213 and they turn off. In this mode the fans are controlled by the coolant temp sensor, located in an impossible position down low in the rear of the block, a bit in front of your gas pedal foot (for reference). With some A/C or DEFROST function set, the compressor runs and fans run in SLOW all the time, so the temp should sit at 12 o'clock or maybe a needles' width or two past.

In any mode, A/C or not, the car should run at 200 - 206 all day long on the highway, and with A/C OFF it will cycle up and down in traffic.

The proper thermostat is set to begin opening at ~188 and be fully open at ~206.

Nuke, huh ?? Surface or sub ??

avatrx

Discussion Starter · #18 · Jan 20, 2011

The proper thermostat is set to begin opening at ~188 and be fully open at ~206.

Nuke, huh ?? Surface or sub ??[/QUOTE]

Surface - George Washington, but most of his school buddies were sub. one of the guys was in the sub that hit the underground obstruction. A good friend of his died in that........... Luke is now out of the Navy and living in MInnesota. Some of my sons buddies are still in...........

on the car:
So far so good this morning. Bill changed the thermostat yesterday afternoon. the gaskets on it were really goofed up which we surmised could have happened due to an overheating event but the car didn't get over 180 on his 7 mile trip to the shop this morning. He has to go to wonder lake to see if Valentine repair can help him fix his chain saw so he'll check the temp as he comes and goes. We haven't put in the cooling sensor as of this point. just changed the thermostat.

He was easily able to find where the thermostat went with help from all of you. The diagram he had from Autozone was way off but your directions were right on target.

-susie

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Submariner409

· #19 · Jan 20, 2011

Good to go - you mean SAN FRANCISCO ??? Happened on a fast and deep run enroute Guam to Australia. Uncharted seamount. Killed 1 and hurt 40. Made it back to Guam under her own power. She's back in commission, BTW. (Notice the bulge in the outer sheathing, just under where the guy is standing........)

avatrx

Discussion Starter · #20 · Jan 20, 2011

submariner409 said:
Good to go - you mean SAN FRANCISCO ??? Happened on a fast and deep run enroute Guam to Australia. Uncharted seamount. Made it back to Guam under her own power. She's back in commission, BTW.

That would be the one! I remember him telling us when he found he would be stationed in Guam we asked him about the snakes. YUK! Apparently there are lots of them. Not somewhere I'd like to visit...............

I remember seeing that photo and some others. I think, If I remember right, at that point he was sent stateside because of his injuries.........

I come from a long line of Navy. Dad - Navy pilot WWII , Korea, ----Mom - Lt CMNDR - WWII,---- brother - retired CMNDR - Vietnam war era and Lebanon crisis stuff. (now working at an 'I'd tell you what I do but then I'd have to kill you" job in Dallas.) And then, my son - Nuke - only stayed in 6 years and happy to be out.............

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