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41K views 59 replies 15 participants last post by  Paul London 
#1 ·
I bought a 99 seville in Jan. with 108,000 miles. I drove to Kansas City, MO from Wisconsin two days after I bought it (moved). The car drove fine. The first weekend I drove downtown the car overheated. I found some threads online that say it is the head gasket. I brought the car to a cadillac dealership and they said "yes it is the head gasket". I brought the car to another place and they ran a test (mixed some liquid with the coolant and did not see a color change) and found not to be a head gasket. This mechanic stated there is nothing wrong with the head gasket and replaced the fan sensore and sent me on my way. One week later I drove downtown and the temp has from the middle about an 1/8 inch (about 3/4 of the gauge). After it raised it went back down after about a minute. When I pull off from a stop light I can hear air bubbles. I need help and hoping this is an easy fix before I drive it back to WI to the dealership to get fixed.

Any help PLEASE!!!!
 
#33 ·
Re: 1999 Cadillac Seville OVERHEATING :(

I had another die test done and the color did change but it took about 30 minutes. The mechanic told me the reason it took so long is because it is a small leak. Does this sound like an accurate assumption? I am just trying to make sure the guy isn't trying to buffalo me :)
 
#34 ·
Re: 1999 Cadillac Seville OVERHEATING :(

Unfortunately, you have a blown head gasket. I have repaired over 20 of these and all have the same symptoms as yours. I repair these for 1500 + parts, so if they only pay 2500, I could get you repaired for less than that, with a warranty. I'm in Ky, which might pose some issues, but you can email me if you have additional questions about your car. Mikelawson@ctky.com.

Mike
 
#35 ·
Re: 1999 Cadillac Seville OVERHEATING :(

right i just got mine and i just replace the radiator the water pump and the thermostat and its still over heating and when it does get hot i have no hot air or cold neither so i think i have a air pocket in it somewhere but I've tryed bleeding it out is there some other or special way to do so??
 
#36 ·
Re: 1999 Cadillac Seville OVERHEATING :(

right i just got mine
This is a heck of a way to say "Welcome Aboard !!!!!!..............:welcome:"

Before buying the car you needed to do some testing.........You now have a LOT of homework to do. If you have replaced most of the cooling system and the engine still overheats, then you have big problems. 1999 is the worst year for Northstars with blown head gaskets. Where did you buy the car, did you pay close to dealer Blue Book retail for it, and is/was there any warranty ??

Check the purge line for steady flow - with the engine cold, remove the line from the nipple at the reservoir top side and hold it in the open filler neck. Have an assistant start the engine and let it idle. No flow and, YES, you have air trapped in the main cooling system. Clean out the purge line and the metal bolt/nipple at the rear side of the thermostat housing/water pump cover. If the purge line is totally clogged it can be replaced by a proper sized length of reinforced fuel line from any parts store. BUT, if it IS totally clogged, the chances of someone having poured some sort of block sealer in the engine are very good - and that's NOT good for you - $$$$.$$

You should do a cylinder block test for exhaust gas in the airspace over the coolant in the reservoir - proper coolant level is halfway up in the reservoir, cold. www.sjdiscounttools.com/lis75500.html
 
#44 ·
Re: 1999 Cadillac Seville OVERHEATING :(

My shop has successfully repaired 98 Cadillacs with bad head gaskets, most had new water pumps, radiators, hoses, and fans etc etc. by the time they got to me. Unfortunately its usually the head gaskets. I have seen a couple that the test showed good but still had blown head gaskets. I have only tested 5 cars with the test as most are easily diagnosed without the test. Whoever fixes it make sure it gets inserts or studs or it will be time wasted. Not to mention money wasted.:tisk:
 
#46 ·
Re: 1999 Cadillac Seville OVERHEATING :(

My shop has successfully repaired 98 Cadillacs with bad head gaskets, most had new water pumps, radiators, hoses, and fans etc etc. by the time they got to me. Unfortunately its usually the head gaskets. I have seen a couple that the test showed good but still had blown head gaskets. I have only tested 5 cars with the test as most are easily diagnosed without the test. Whoever fixes it make sure it gets inserts or studs or it will be time wasted. Not to mention money wasted.:tisk:
Mine got a new overflow reservoir (the first thing to go)...then a water pump......two hoses.....then radiator.....then heater (a fun and messy failure....)...then another hose......so I didn't bother with the "test"....pulled the engine...and upon pulling the heads, the failure was OBVIOUS.

I think my failure happened over a pretty long period of time...it didn't just fail massively one day.....symptoms just got worse...and worse and worse...
 
#48 ·
Re: 1999 Cadillac Seville OVERHEATING :(

Good evening; Guys i just got threw re-doing a 1999 Cad. Seville STS semi complete cooling system that is redoing the water pump housing gasket, therm. replace, radiator new out the box, coolant temp. sensor,100% antifreeze not 50/50.
But every time i drive it on the highway it shows half gauge, after getting off the highway and driving about 3mins. it starts to climb in temp. 6mins. off highway its running hot, my fan are coming on both of them, but it still rises in temp., but it seems that as long as i'm on the highway it never passes half gauge.
Can someone guide me in the right direction away from the DealerShip?__.:devil:
 
#49 ·
Re: 1999 Cadillac Seville OVERHEATING :(

:welcome:

Guide you to where? Diagnosis or repair?

For diagnosis first check the purge line. If that's clear get a block test kit. You can borrow one from AutoZone. Run the test per the instructions to check for exhaust gases in the surge tank. Being a '99 I would not get my hopes to high though. Unfortunately, like many people you probably wasted a lot of money, time and effort throwing parts at it hoping one will stick.
 
#50 · (Edited)
Re: 1999 Cadillac Seville OVERHEATING :(

.......... and 100% coolant freezes and boils at a lower temperature than the recommended 50/50 mix, and 100% coolant DOES NOT remove as much heat per liquid volume as 50/50. The various "water wetters" will not do a thing for you, so forget that, too.

As Ranger posted, you need to do a thorough cooling system diagnosis and stop throwing parts at it.

Here is approximately the temperatures you're looking at (the tick marks on the earlier 130 degree sweep gauge correspond to the ticks on this gauge). The notations are not applicable to Northstar cooling sysems after 2005.
 

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#52 ·
Re: 1999 Cadillac Seville OVERHEATING :(

Fairly steady flow at idle, increasing in volume as rpm is raised. Spits and sputters that clear up shortly after engine start is a small air pocket being purged. Constant sputtering, with bubbles, is not good. No flow is not good.

A pulsating flow with no bubbles is probably OK, but flow should smooth out as engine rpm is increased.

...........remember - correct coolant level in the surge tank is half full, cold. Don't check/adjust level with the engine any more than barely warm.

Welcome to the Funny Farm!! You must have your site viewing preferences set to "View oldest posts/threads first". This thread had been dead for 4 years.
 
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#54 ·
Re: 1999 Cadillac Seville OVERHEATING :(

Fairly steady flow at idle, increasing in volume as rpm is raised. Spits and sputters that clear up shortly after engine start is a small air pocket being purged. Constant sputtering, with bubbles, is not good. No flow is not good.

A pulsating flow with no bubbles is probably OK, but flow should smooth out as engine rpm is increased.

...........remember - correct coolant level in the surge tank is half full, cold. Don't check/adjust level with the engine any more than barely warm.

Welcome to the Funny Farm!! You must have your site viewing preferences set to "View oldest posts/threads first". This thread had been dead for 4 years.
but there's life in the old thread yet: it's helped me 'cos it gave info. I'd not seen elsewhere.

Replacing the pressure cap (NOT cheap here) stopped the water coming out of the surge tank & then replacing the 'stat meant the bottom hose felt only a little cooler than the top one (whereas before it was barely warm) that leaves the purge line (following Sub's advice elsewhere not to throw money/parts at it) which clearly needs attention: before I did the 'stat it spluttered (like a domestic faucet after the supply been interrupted) but afterwards - nothing! (at least at idle). I know now what I have to do (although removing the airbox &, it seems, the MAF sensor, to get at the "other" end out in the street, in the dark won't be a lot of fun) AND what, having cleared/by-passed any blockage, I should expect.
 
#55 ·
Re: 1999 Cadillac Seville OVERHEATING :(

If your engine has the coolant-heated throttlebody, those are known to clog and cause purge flow issues.

Bypass the TB circuit and replace the entire purge line with proper sized reinforced rubber fuel line from a parts house. Screw-type band clamps. Be careful wth that plastic surge tank nipple.

Coolant heated throttlebody ???? Theory says that, with the throttle blade almost closed - idle speeds - the rapid expansion of the air on the vacuum side of the throttle blade can cause ice formation on cool, humid mornings. Heat the throttle bore. Old carburetor stuff - the heat riser - did that as well as assured cold fuel atomization. But we have port fuel injection. Our throttlebody is bolted to an aluminum water crossover so it naturally heats as the coolant does so. Heated throttlebody = redundant, and it lasted only 2 years or so.
 

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#56 ·
Re: 1999 Cadillac Seville OVERHEATING :(

If your engine has the coolant-heated throttlebody, those are known to clog and cause purge flow issues.

Bypass the TB circuit and replace the entire purge line with proper sized reinforced rubber fuel line from a parts house. Screw-type band clamps. Be careful wth that plastic surge tank nipple.

Coolant heated throttlebody ???? Theory says that, with the throttle blade almost closed - idle speeds - the rapid expansion of the air on the vacuum side of the throttle blade can cause ice formation on cool, humid mornings. Heat the throttle bore. Old carburetor stuff - the heat riser - did that as well as assured cold fuel atomization. But we have port fuel injection. Our throttlebody is bolted to an aluminum water crossover so it naturally heats as the coolant does so. Heated throttlebody = redundant, and it lasted only 2 years or so.
Forum site let me down again, almost finished reply yesterday when it froze - & at about the 3rd attempt to get cursor to move, the site just disappeared off the screen.

Oh well, here we go again: yup, knew that hence the current &, probably, final phase in tackling this problem. Of course you couldn't have known that, so it's not that I'm not grateful.

Had already printed off an enlarged copy of that diagram, to keep by me when I start dismantling. I now know I have the heated TB, because the line from the surge tank ends on a vertical pipe. I now also know where to be looking for the other end, to lead me to the infamous hollow bolt.

Couple of details though, how much pipe do I need to do the bye-pass job? I'd like to get it before I further disable the car & why do you say fuel line? Short of going to a truck dealer I'm going to have difficulty getting some with anything like that i.d. - 8 or 10mm seems to be about the norm here.
 
#57 ·
Re: 1999 Cadillac Seville OVERHEATING :(

Reinforced rubber fuel line comes on large spools in many different ID sizes. Use a length of it - proper ID - and go straight from the hollow bolt/nipple over to the surge tank. Use screw-type band clamps - fuel line size.

Why reinforced fuel line??? Because it is tough and easily withstands any normal cooling system pressure.

5 second quick search ..........

https://www.amazon.com/s/ref=nb_sb_...ld-keywords=automotive+rubbber+fuel+line+hose
 
#58 ·
Re: 1999 Cadillac Seville OVERHEATING :(

As far as I know, it only comes in 6,8 &19mm ID here for automotive use, so, depending on what I can find, it looks like ordinary coolant pipe for me - & I'm certainly not going to buy a spool of it, I begrudge having to buy a metre, but I suspect that's the minimum.

Off to a restoration show in a couple of weeks (poor substitute for a weekend in LA - but there you go) so there'll be a couple of specialist traders there, I can wait that long now, so I'll see what i ca find.

You've mentioned clips before, not a fan of Detroit's staple fitting then (just as BMW & the French are latching on to them)?
 
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