: Northstar overheating



morerevs
11-24-03, 11:11 AM
I have a '97 Concours with 88K that has overheating problems, I was hoping to get some insight from the loyal Cadillac bretheran. I recently had the water pump housing seal leak, and I replaced it along with the water pump(I also had the fuel rail line pop a pinhole leak, but that's another story!). Upon completion, I refilled the cooling system, but was unaware of the magic pellet requirement. The car performed flawlessly for a week, driving around town(LA). On the weekend I attempted to drive to Vegas for a wedding, and got about 100 miles before the car overheated. I was aware of the 'limp home' mode, so I drove about 4 miles at low speed to get it off the highway. I noticed that despite the coolant blowing out of the overflow hose that the left (exit) side of the radiator was cold. I figured that the thermostat was stuck, so I had it replaced. I also changed out the radiator cap also. The service garage also did a combustion leak check. I'd never seen this test before, they used a clear cylinder with some dye and placed it over the filler neck while the coolant was hot and boiling over. They had it on for about 30 seconds, and the dye didn't change color, indicating there wasn't a combustion leak. Was this enough time to tell? I am not sure, I've never seen the test before. Anyway, we replaced the 'stat and the car still overheated. To get it home, we gutted the old 'stat and drove very slowly, keeping the temp at mid-gauge. I didn't get any smoke out of the exhaust on restarts. My gut feeling is that the rad is gunked up, maybe due to my not adding the pellets. So, my question is, does anyone else have any insight or suggestions, and if my rad is gunked up, what is the best way to clean it out? Thanks in advance.

zonie77
11-24-03, 12:45 PM
When my brothers N* started having problems he did a lot of coolant repairs before the coolant leak test and it turned out most of them were a waste. Which is why I keep telling people to have the test done early in the process.

The last time he drove it far was to Vegas and he wound up getting towed halfway back!

One thing we thought of doing, but didn't get to, was to put in a section of clear tubing in the upper rad hose to check coolant flow. He did put a new radiator in which did not fix the problem.

The pellets (Bars leak) helps seal small leaks and should not clog the radiator if used in small amounts and you occasionally flush the coolant. Not putting them in will not clog the radiator.

I don't want to waste your time or money but it would be interesting to redo the test after the coolant was in it a while to see if it shows positive.

Another thing is when the gaskets first start leaking they seem to be inconsistent. They'll seal awhile, then under the same driving conditions they won't and cause overheating.

When you got home were you low on coolant?

morerevs
11-24-03, 01:00 PM
Thanks for responding to my post. To answer your question, I can't be sure if the car lost coolant on the way home, because the car overheated climbing a hill right at the end of the trip. For 75 fairly flat miles the car was fine, right at mid-gauge. It's possible it could have been leaking then, or, it could have just blown out at the very end. When the car was overheating, I looked under the car and couldn't find any signs of coolant drips.
I wasn't aware that the pellets were merely 'bars leak'. I thought they were something special for aluminum engines, some sort of special lubrication. I also did not install the factory coolant, having read on the Prestone bottles that they were approved for all engines, including aluminum. I was thinking that this, along with the lack of pellets were causing the problem, since there was also a mention in the owner's manual that using non-factory coolants could cook the engine(checked the manual too late!).
thanks,

Martin

zonie77
11-24-03, 07:53 PM
You're welcome.
Good Luck and let us know what fixes your car.

baconn_1
03-12-04, 06:53 PM
You have described the same problem that I am having with my 97 Deville. The 100 miles, the overflow boiling over, etc. Any resolutions? the dealer is trying a stat right now. Doesn't sound like the problem.

Was the radiator the issue?

TIA

jb

BeelzeBob
03-17-04, 10:56 PM
I have a '97 Concours with 88K that has overheating problems, I was hoping to get some insight from the loyal Cadillac bretheran. I recently had the water pump housing seal leak, and I replaced it along with the water pump(I also had the fuel rail line pop a pinhole leak, but that's another story!). Upon completion, I refilled the cooling system, but was unaware of the magic pellet requirement. The car performed flawlessly for a week, driving around town(LA). On the weekend I attempted to drive to Vegas for a wedding, and got about 100 miles before the car overheated. I was aware of the 'limp home' mode, so I drove about 4 miles at low speed to get it off the highway. I noticed that despite the coolant blowing out of the overflow hose that the left (exit) side of the radiator was cold. I figured that the thermostat was stuck, so I had it replaced. I also changed out the radiator cap also. The service garage also did a combustion leak check. I'd never seen this test before, they used a clear cylinder with some dye and placed it over the filler neck while the coolant was hot and boiling over. They had it on for about 30 seconds, and the dye didn't change color, indicating there wasn't a combustion leak. Was this enough time to tell? I am not sure, I've never seen the test before. Anyway, we replaced the 'stat and the car still overheated. To get it home, we gutted the old 'stat and drove very slowly, keeping the temp at mid-gauge. I didn't get any smoke out of the exhaust on restarts. My gut feeling is that the rad is gunked up, maybe due to my not adding the pellets. So, my question is, does anyone else have any insight or suggestions, and if my rad is gunked up, what is the best way to clean it out? Thanks in advance.

Are you positive that you have a 50/50 coolant/distilled water mix in the system...??? Check the coolant concentration with an accurate tester to be positive. I have heard of several overheating problems where the problem was traced to a "weak" coolant mix. If the system is not filled with 50/50 (protected to -40 freezing on the tester) then it can boil prematurely within the normal operating range of the system IF it had 50/50 in it. This premature boiling appears as an overheat but it is simply the weak coolant boiling well below the point that it should.

A 15 PSI pressurized system with 50/50 coolant/water mix can operate to 265 F before it boils over....so if yours was not that hot then it shouldn't have boiled......

The other thing to check is for an obstructed vapor vent line from the water pump. If you look at the upper radiator hose at the engine end you will see a nipple with a 3/8 hose immediately beside the rad hose. With the system cold, take the 3/8 hose off and start the engine. You should observe a steady stream of coolant out the nipple on the engine. The nipple is really a hollow bolt...if coolant is NOT peeing out the nipple when the engine is idling then remove the bolt and determine what is plugged up. Possibly a piece of debris or sealant got lodged in the orifice when the previous repair was made. If the water pump cannot vent actively it will develop a vapor pocket and stall the pump. If coolant pees out the nipple then reinstall the hose and go to the pressurized surge tank. Find the 3/8 hose connected to the surge tank. Take it off. Start the engine again. Coolant should stream out of the hose....if not, the circuit from the engine to the surge tank is plugged up somewhere. Find and repair.

morerevs
03-18-04, 01:12 PM
Thanks for taking the time to send such a clear and detailed response. That info would have helped greatly when I was diagnosing my problem. Hopefully someone else can benefit from your suggestion. Unfortunately, my car had a combustion gas leak------>head gasket.
Thanks again