: Coolant Temperature Problem

12-03-12, 04:33 PM
This is my first question on this Forum, and I'm not quite used to navigating it yet.

I have a 94 SLS Northstar. It had 96k miles when I first got it 4 years ago, and had been VERY well maintained by the second owner, who put most of those miles on it ... but it had a slight leak somewhere in the coolant system, so that every couple of months, the 'add coolant' light would come on, but it never took much water/antifreeze mix to refill it ... maybe a quart each time. Over those four years, I've put another 22k miles on it. I put those little pellets in the radiator maybe 4 different times because it kept leaking, and eventually, six months ago, my water pump gave out. I just got around to changing it yesterday, along with the thermostat and the upper hose. I started it up, and it seemed to warm up normally. (Until the water pump quit, it normally ran in the 182-195 range.) The thermostat appears to be opening, but I drove it on the highway for less than a half mile before it got up to 220, so I turned around and drove back home. I let it idle in the drive until it got to 230, and I shut it off. What could be the problem? Could there be an air bubble, or does it need a flush? Any help would be greatly appreciated.

12-03-12, 04:54 PM
The "purge line" may be plugged with your tablet residue (GM quit using them). The purgeline is the mechanism by which trapped air is removed from the main cooling system and sent to the airspace over the coolant in the reservoir. The line runs from a hollow bolt/nipple at the water crossover near the water pump cover over to a nipple on the upper side of the coolant reservoir. With the engine cold, remove the line from the reservoir nipple, place it in the open reservoir neck, and have an assistant start the car normally. A steady stream of coolant should flow to the reservoir. If it doesn't then either the hollow bolt/nipple is clogged (clean it with a hand-twisted proper sized drill bit - 2.5" deep) or the line itself is clogged. Clean it out. If you cannot clean out the line it may be replaced with a proper sized length of reinforced fuel hose and band clamps from any parts store.

With no A/C function set the cooling fans should go to SLOW at 224 and to fast at 236. With an A/C or DEFROST function set the A/C compressor runs and fans run in SLOW all the time.

12-03-12, 05:10 PM
Submariner, thanks for your quick reply, and for your very specific answer. I could visualize what you were saying. I'm an ex-nuke, but I broke my femur at Sub School, so I wound up on the surface. I don't know if I'll get around to this today, but I will reply with the results when I do. BTW, do you think the system should be flushed? I haven't done so since I've owned it, and I couldn't even find the petcock on the radiator when I changed the water pump. (I'm disabled, so it's difficult for me to get down on the ground, and back UP) If you recommend it, is there a procedure outlined in this forum? Thanks again.

12-03-12, 05:39 PM
For the twisting and rolling you need to do to effectively drain and clean this cooling system, may I suggest you get to a GM dealer and take advantage (???) of a "Fall fluids special" (coolant, brake fluid, P/S fluid, transmission) or at least a total coolant exchange - they use a pressure/vacuum machine that completely exchanges ALL the coolant (you cannot do that in the garage). Yes, the whole package is over $400 and the coolant exchange, separately, will be ~150, but it will be done correctly, with an invoice and service warranty.

Not sure, but there may be a drain valve (for contortionists) under the driver's end of the radiator.

I went through Sub School in 01/58. Diesels, fast attacks, staff, missile boats. Chief Of The Boat in USS SAM HOUSTON (SSBN 609) AND USS JAMES K POLK (SSBN 645). Retired as Command M/C, US Naval Academy in 02/82.

12-03-12, 06:13 PM
U had thermostat out so u lost a lot of coolant. Or rather the system got drained a lot. U can only add so much initially and should do a short trip locally to heat up motor. U may even get a low coolant message. Head home. Wait for it to cool and add more. U can pull lower both rad hoses and flush out rad if u want but it does not hold much.

12-03-12, 06:29 PM
I Sa LUTE you, Master Chief ... lol. Here's the deal, like I said, I'm disabled ... I'm 63 and drawing SSD and a small VA pension. I live in the sticks, 45 miles from the nearest dealer, and my 29 year old sometimes employed son moved back in with me AGAIN almost two years ago ... Times are 'tough' ... lol. I'd just like to get MOST of it out, and then maybe flush and replace the coolant/mix a couple of times in the next year. I was hoping and praying ever since I got it, that that LEAK wasn't from a CRACKED BLOCK ... and I'm HOPING to at least try to baby it until I'M done on this Earth. Can you point me to the petcock, and maybe a step by step list of how to flush it. I was a pretty fair shade tree mechanic back when cars were much simpler. I do have access to some young mechanically inclined neighbors, and I have a decent set of tools.


Submariner, I went to SS in April of '71 in Groton. I broke my femur playing beerball down there below the EM Club. I had orders to the Daniel Boone (can't recall the hull number), but they put a pin in my leg, and I had complications with it, and after it healed and they removed the pin, they decided it would be detrimental to me (AND the crew, I guess) on a Boomer, so they sent me to the surface, and I still never finished Sub School. I was looking forward to it.

12-03-12, 10:40 PM
Can you point me to the petcock

#8. (drivers side) Probably easier access by removing the lower splash shield. Flushing it is pretty hard. You're better off just draining what you can and refilling with 50/50 coolant and distilled water and don't use those tabs any more.


A slow leak might well be a cracked radiator side tank or surge tank (not uncommon on a car that has had many heat/cool cycles).

12-04-12, 12:43 AM
Thanks, Ranger. I guess I didn't see the petcock because I didn't change my lower hose. Since I've already used 50/50 coolant cut a little with regular water, I may hold off on the distilled water mixture for two or three months, and I'll try to flush it then. I'm going to check that purge line tomorrow to see if it's plugged, and I'll report back. Thanks again.


Ranger, what is # 6? Is that a gasket for a 'side tank'? Because I still have a small leak on the passenger side of my radiator, and I haven't determined where it's coming from yet. I'm hoping it dripping from the bottom of the upper hose I changed, and that I may not have tightened down all the way ... because it wasn't leaking there before.

12-04-12, 08:32 AM
The end tanks are crimped to the aluminum core - #6 is the "gasket" between the tank and core edge.

FWIW, rather than attempt to repair an end tank gasket leak (or crack), replace the entire radiator. At this point in time it's cheap insurance.

(How about ENTERPRISE going out of commission ? My son in law was the Engineer (Reactor Division) in her for 3 years, then he went to THEODORE ROOSEVELT. He retired on 22 and now works at supervising essentially the same jobs for NR in NORVA.)(I was a QM except for an early 2.5 years as an IC Electrician)

12-04-12, 08:36 AM
The side tank can crack. It can leak at seal. It can leak at tube/fin point and end up dripping by side tank and appear to be leaking there. If u see coolant u can assume tank is cracked after 18 yrs. u can get new aftermarket rads for 60-125 or spend 225 for a delco. Maybe the delco uses better plastic but I think they still r made in Malaysia? Unless someone here can provide info on delco manufacturing.

12-04-12, 10:35 AM
Ranger, what is # 6? Is that a gasket for a 'side tank'? Because I still have a small leak on the passenger side of my radiator, and I haven't determined where it's coming from yet. I'm hoping it dripping from the bottom of the upper hose I changed, and that I may not have tightened down all the way ... because it wasn't leaking there before.
Sorry, I should have included the part breakdown, but I'd follow Sub's advice on replacement. Chances are the other side is no better.

12-04-12, 12:16 PM
I heard about the Enterprise ... don't even get me STARTED about what's going on with our military right now.


Wow ... actual GM drawings for my specific vehicle ... That's SO much better than a Chilton. Thanks.

12-04-12, 02:46 PM
Bucu, for future reference you can find those diagrams at either of these two sites.

I seem to find this one more accurate. Once you find the car and then the correct section, click on the blue INFO button for the diagram.

This one is almost the same (most of the time), and has the full part numbers.

Chiltons and Haynes are very generic and pretty useless for anything but the most basic things. We always say they are best used for sopping up spilled coolant or trans fluid or lining bird cages (They're too coarse for toilet paper). If you want a REAL Cadillac repair manual, get yourself a FSM by Helm Inc. Ebay is your friend.

12-04-12, 03:46 PM
Thanks Ranger, I wish I had this long ago. I don't want to mess up the coolant system. If I mess up this engine, I might as well weld a tow bar to the front end, and use it for a utility wagon ... of course I won't have anything to PULL it with ... lol.