: Head vs. intake manifold gasket/overheating

04-06-04, 12:19 PM
I was tempted to attach this to the fascinating thread on head gasket probs but I'll start anew...
Somebody (not the dealer) who's worked on a couple of N*s looked at my disappearing coolant problem (no 'droppings; topping off with a gallon every 2 weeks) and suggested that it might be the intake manifold gasket allowing the fuel injectors to spray fuel into the coolant (and coolant to be burned off). He looked at the clean, clear oil and downplayed head gaskets. This was just a curbside consult cuz I could not leave the car, but he said he'd do a compression check on the head gasket to isolate the prob and that the last N* intake manifold gasket he'd done was about $750
Does this sound reasonable? The car does not run with any loss of power that I can detect, which I would assume would be there due to loss of compression if it were the heads. It does run hot (up to 259 yesterday when I left it idling for 20 minutes after 15 minutes at 60; normally about 204 on my daily 6 mile drive). Coolant was changed last summer with Barsleaks and I added another bottle recently with no noticeable change in behavior. Thanks in advance!

04-06-04, 01:12 PM
Find a new mechanic.

$750 for intake gaskets is a rip. He obviously has never done one.

And there is no coolant around the intake ports or injectors to leak there either.

You should take it to another shop and have the head gaskets checked.

Have you checked the cooling system? Thermostat, radiator, water pump and drive, pressure cap? If it is over heating from one of these things it will loose coolant.

04-06-04, 01:59 PM
When you start the car after sitting all night does it sound and or feel like it is missing at first?

04-06-04, 03:10 PM
Starts and runs like a champ, without missing...the only thing about the running is the sound...it sounds, well, like aluminum--that kind of grating sound...prob more related to the age of the engine than the coolant probs? Would a miss imply the intake gasket prob?

04-06-04, 04:18 PM
It is almost never necessary to replace the Northstar intake gaskets. They are a steel shim type with raised silicone beading on both sides. An exception would be if you removed the intake manifold and bent one, or if you were replacing the head gaskets, I would do them at that time.

It would take about an hour to raise (not remove) the intake, slip out the gaskets, and do a little wiping down. There is no coolant running through the intake on a Northstar, there are no coolant openings under the intake manifold to be exposed by loose inake bolts.

A little sputter after setting overnight or a few hours might indicate coolant in the cylinder. This coolant is rapidly blown out and then the engine will usually run fine.

The coolant is going some place, it does not evaporate in a closed system.

If it is not leaking you are sucking it into the cylinders and it is going through the ignition cycle. It sounds to me like your head gasket(s) are failing. This is an expensive repair. You should get your coolant checked for hydorcarbons and pressure tested to confirm or eliminate this possiblity.

I am replacing head gaskets on one of my 93' STS right now. It gradually started using coolant with no visible signs. Before I tore it down it would go through 2 1/2 gallons of coolant within 20 miles, and still run great; until it went into the limp home mode.

Do yourself a favor and get the checks done before getting stuck somewhere or before damaging the engine.

-Good luck,

04-06-04, 05:08 PM
growe3A little sputter after setting overnight or a few hours might indicate coolant in the cylinder. This coolant is rapidly blown out and then the engine will usually run fine.

The coolant is going some place, it does not evaporate in a closed system.

Yes mine does/did/depends has a miss when it starts after setting for a day especially if its cold. It's not doing so bad now because it's getting warmer. I am currently assembling another engine to swap out the one in my car, along with the torque converter.

04-06-04, 08:35 PM
Well, for a few hours there I was tickled to think maybe I had a problem NOT requiring yanking the motor but you folks have convinced me that it's most likely the head gaskets...I would love to throw this work at a local mechanic just cuz $1-2k means a lot more to him than it does to the dealership (no offense) but I'm coming up empty as far as someone who knows what they're doing AND wants to do it...
Can anybody recommend a shop in the Boston area that could handle this job? I understand Frost Cadillac to be pretty good, but I know how big this job is and $75/hr adds up fast! Thanks, again, to all!

04-07-04, 02:08 PM
And last but not least, a call to Frost Cadillac yields a service manager who tells me he won't even look at it because of the high miles (128k) and couldn't my regular mechanic do it and I should just keep driving it till it dies...Thanks to Growe3--I wasn't aware of the architecture of the engine enough to know there's no water near the intake manifold...guess I'll be driving on Barsleaks and Prestone 50/50 until I get my 7k out of her (about 14,000 miles, and I've already got 6k).