View Full Version : Head Gasket on 99 STS

11-27-05, 12:38 PM
Okay, I've been reading about the head gasket problems on these N*s for a couple of days now since my wife's car overheated the other night after being in some traffic. The car runs great! I've checked the purge line and cleaned out the recovery tank to make sure that's okay. Things are kindof torn apart right now because I've been trying to do a leakdown test but the flexible hose on the typical tool you buy for that doesn't allow you to tighten it enough to avoid leakage at the plug hole. So, I'm off to find a 6" piece of 1/4' pipe for the fitting I bought for it which is too short.

Anyway, I'm thinking that if this car only overheats when it's in heavy traffic, and has only 54K on it, it should be fine to just watch it and use it around town, or even on the freeway as long as it's not stop and go driving for extended periods. I'm thinking it's a shame to spend the money and go to the work of dropping the motor and doing the headbolt thread repair without doing other things that it just isn't ready for yet. It's doesn't sound like a fun enough job to do just for the kicks! Plus, it sounds like you only get two shots at the thread repair and doing it now effectively shortens the life of the block.

I've got a couple of other cars to depend on, just hadn't planned on pressing them into daily "can't get to work if this car doesn't start" mode. I could spend the same money on my truck to act as another backup (I have a forty mile commute each way) if my wife had to resort to driving my Deville every day.

I'm just not excited (and thourougly ticked off) about this kind of failure at this mileage point on a car that I bought so she could be confident whenever she gets in it for many miles to come.

Just wanted your input on the idea of just driving the thing and watching it for a while.

11-27-05, 01:06 PM
Thats a shame. Its a nice car you bought for your wife..i bet its not the gaskets though, couldve just been a fluke thing or even maybe check the thermostat?? My thermostat was bad before, it would go to 280 and say engine hot..a/c off on the DIC. Does the block feel really hot after this, like hotter than normal? These are all dumb questions I know, because you obviously have a lot of mechanic skills if you can do a headgasket job yourself; but just merely pointing it out. :)

11-27-05, 05:14 PM
If it's overheating in traffic the fans may not be working. Check them first. They come on about 220deg or when the AC is on.

Verify water pump belt/tensioner working and purge line is clear.

11-27-05, 05:31 PM
As mentioned, check the thermostat as well as the surge tank cap. If it is bad, it may not be holding enough pressure causing an overheat situation. Good luck and keep us posted.

11-28-05, 12:58 AM
Thanks for the input.

I'm gonna put the thermostat in tomorrow while I've got things torn apart. What I didn't mention in this post was that I had it in the shop for coolant flush after hearing a sloshing sound inside the cabin and was told the system needed to be bled to get rid of air. After getting it out of the shop we still could hear the sound and then it overheated. I took it back in and the technician said he detected hydrocarbons and CO2 in the recovery tank. That's indicative of a head gasket problem. He also said it wouldn't overheat for him and the fans worked for him too.

So, we'll see. I figure for 15 bucks it can't hurt to change the thermostat anyway and finish the leakdown test. Then I'll drive it again and see what happens.

11-28-05, 01:14 AM
I'd only recommend a GM thermostat.

I drill a small hole through the moving disc to reduce the chance of an air pocket (if it doesn't already have one...no bigger than 1/4").

12-28-05, 11:25 AM
Just thought an update was in order.
I put a thermostat from Auto Zone (confirming the design with small hole was the same) in and cleaned out the recovery tank and purge line. Now the car seems to be okay. My wife said she sat in heavy traffic for about 45 minutes yesterday and the temp showed normal. Thank God!! I got a quote from a local former Cad mechanic of $2500 for the gasket job which seemed reasonable to me but I'm glad to not be spending the money especially since I got layed off just about 2 weeks ago.

Thanks for all your input.


12-28-05, 04:07 PM
Great! You got a nice Christmas present.

12-31-05, 05:20 AM
sell it immediately. it will just get worse and stick you with an expensive repair or worthless car. i waited too long on mine and it broke my heart.

Harry Yarnell
12-31-05, 09:46 AM
My wife got stuck in Baltimore traffic a year ago, and the coolant fans didn't come on (blown fuse). Gauge went into the red and the alarm went off. She was wise enough to park the Eldo and call a hook. The gaskets didn't blow. Runs good as we speak.
Oh, another check for a blown gasket is to look at the engine oil on the dipstick. If it's chocolate milk looking; blown headgasket.

12-31-05, 12:40 PM
I think "Rob" had mentioned before that due to the Northstar design, a blown headgasket will rarely, if ever, put coolant into the oil.

STS 310
01-03-06, 05:09 PM
sell it immediately. it will just get worse and stick you with an expensive repair or worthless car. i waited too long on mine and it broke my heart.


Maintain it, drive it, and enjoy it.

Dont get paranoid, its a waste of time.

Harry Yarnell
01-03-06, 05:59 PM
I beg to differ. A blown headgasket will allow coolant into the cylinder(s) and past the rings, into the sump. A blown headgasket PROBABLY woun't let oil into the coolant. Perhaps that's what 'Rob' meant.

01-03-06, 07:06 PM
The design on the N* MINIMIZES the coolant getting into the oil. It is different than older blocks in the oil drainback location and the fact very little oil goes to the heads.

It is me that keeps saying looking for coolant in the oil is not a good indicator on N*'s. Oil holds a certain amount of water before it is obvious as a gooey mess. By the time it gets to that point the gaskets are literally "blown".

Harry Yarnell
01-03-06, 07:28 PM
If you've ever had a Northstar apart, you'll see that the coolant passages are only seperated from the combustion chamber by the 1/8" ring of steel in the headgasket. When it fails, coolant pours into the cylinder; what's not to understand how coolant gets into the oil?

01-03-06, 08:08 PM
I've had several apart and I'm aware of the relationship. When running the majority of the coolant will be expelled with the exhaust. I agree some will get into the crankcase but it will be a relatively small amount. It will not be obvious by looking at the oil.

None of the one's I've seen exhibited any coolant in the oil. Most of the people with head gasket leaks didn't see this unless the leak got extremely bad.

I'm not saying it doesn't happen, just it won't be enough to be a relaible indicator.

01-03-06, 08:11 PM
I think what you're saying is it will get past the rings like blowby? That would be very minimal...

Harry Yarnell
01-03-06, 09:00 PM
The one I'm installing now had two cylinders with bad head seals (headgasket) and the oil was loaded with coolant.

01-03-06, 09:18 PM
Then it probably was driven that way quite a while. Did you buy it that way?

01-04-06, 05:43 PM
Harry, give us some info on the N* your are talking about. Do you know how long gaskets were leaking? When last oil change was done?

Harry Yarnell
01-04-06, 06:43 PM
Don't know the history of this '97 Deville; bought it with a salvage title for $500. Beautiful Polo green and nice interior, but yes, someone apparently drove this rascal for som time with the bad gasket. In an attempt to 'repair' the blown headgasket, they dumped a TON of sealant into the coolant. All that did was plug up everything EXCEPT the headgasket (go figure).
Engine was completely torn down and boiled out. Hone marks are still visible on the cylinders. Bearings were perfect.
I've just finished installing it in the car today. Hopefully it'll be running shortly.

Harry Yarnell
01-04-06, 07:25 PM
Zonie, where in Arizona are you? We're heading to Tucson in a few weeks.

01-04-06, 10:11 PM
North of Phoenix. Doing anything special in Tucson?

We are on the same page on this, some one drove that one a long time without changing oil. My point was you don't see the water in the oil until the gaskets are pretty bad. Not as quickly as in older cars.