Overheating

k63d400 · #1 (**permalink**) 04-15-07, 05:58 PM

1994 Concours with 156k miles
Today my car began to over heat once again.

It runs fine for 30-40 mins @ 95-100 C then it begins to climb to 125 at which point i shut it off.

The thermostat, surge tank cap and water pump pully are new, as are the hoses. The bypass line going into the surge tank flows freely. The water pump spins free and loose when you turn it by hand.

Today the heater was set to max and when it began over heating it went cold and the coolant temp began to climb.

Could the water pump be bad?
I do not have a spring in the lower radiator hose but the auto store assured me that one was not needed because the new hoses resist collapsing.

misfit6794 · #2 (**permalink**) 04-15-07, 07:04 PM

Yet another northstar overheating issue, someone should write a book. Search the forums for headgasket (s). See if you have any of the signs. ALthough if it were, I think the car would overheat much quicker. It could be on its way to failing tho. Could definetly also be a water pump though. Thats not a fun job either.

**Playdrv4me** · #3 (**permalink**) 04-15-07, 09:40 PM

Odds are not in your favor that it wont be headgaskets, but you got plenty of good miles out of that motor.

Check the surge tank for bubbles, then have a cylinder leak down and exhaust gas test done to the coolant.

lenny lincoln · #4 (**permalink**) 04-15-07, 09:46 PM

I dont know northstar motors , But i do know motors, sounds like a stuck closed thermostat.

**Ranger** · #5 (**permalink**) 04-15-07, 10:07 PM

Could be several things. As mentioned, do a search for overheating.

**Playdrv4me** · #6 (**permalink**) 04-15-07, 10:40 PM

Quote:

Originally Posted by lenny lincoln

I dont know northstar motors , But i do know motors, sounds like a stuck closed thermostat.

Ahh if only it were that easy... If ONLY. Oddly enough the T-stats in the Northstar motors are about as reliable as the headgaskets should be.

k63d400 · #7 (**permalink**) 04-15-07, 10:48 PM

put in a new t-stat tonight.
also trimmed down the lower radiator hose. the one from the auto part store was a bit to long, caused the hose to pinch closed a bit near the bends.
took it for a 1/2 hr test drive, holdin at 92-100C. Maxed at 106C while idling in the drive way but the fans kicked on and it came down, going for an extended test drive tomorrow....

k63d400 · #8 (**permalink**) 04-15-07, 11:05 PM

Well I've had the car for a good 40,000 miles i guess it time to replace it. In the mean time i only need it to last me another 500 or so miles.
Any suggestions on a new caddy? I like the 1999-2002 Seville SLS,STS and 1997-2002 Deville. I have been saving for a new cadillac, i only need to get a dozen or so 26 mile trips out of my current car.

I've seen those liquid head gasket repair solutions you put in the coolant and run through, would that provide a temorary fix for 500-800 miles???

misfit6794 · #9 (**permalink**) 04-15-07, 11:34 PM

I believe the headgasket issue was addressed on the 2003 and newer northstars, might be wrong. Make sure its the headgasket before you write a death sentence for it. Caddy's aren't the best when in comes to resale so you could probably get a good deal if you have the loot to put down.

**Playdrv4me** · #10 (**permalink**) 04-16-07, 12:46 AM

Misfit is right. Lets make absolutely sure your headgasket is gone before you make any major decisions! Sometimes it works out that like the rest of the world, it just happens to be a T-Stat or a bad hose, but unfortunately not usually on N*'s.

Re: the liquid headgasket fixes. From everything Ive seen here not only do they not provide a fix, they barely work at all due to the construction and alloy used in the NS. Surely if you get to that point and youre just gonna get rid of it anyway, wouldnt hurt to throw it in there, but I advise against it in all but the worst case scenario.

Good luck.

k63d400 · #11 (**permalink**) 04-16-07, 08:32 AM

Thanks for all your help guys, i will repost later today when i get a chance to go for a longer test drive. We'll see if it was the t-stat or hose causing the overheat.

k63d400 · #12 (**permalink**) 04-16-07, 04:37 PM

New T-stat and trimmed the lower hose because it was pinching near the curves. The car it running cool now.. Ran it for 3-4 hours. On the highway its between 88-92C While idling it spikes to 108 for a few min then the fans kick on and cool it down.

**Playdrv4me** · #13 (**permalink**) 04-17-07, 02:13 AM

Congrats!

Keep a VERY close eye on both your coolant level and your exhaust and temp for the next two weeks or so. Coolant level more than anything. If it starts to lose coolant youve got a problem.