View Full Version : 1999 DeVille Coolant leak

05-03-09, 09:21 PM
I have a 1999 DeVille with 156,000 miles on the car. Last winter I had a coolant leak that turned out to be the water pump. I had the water pump and the small belt replaced. That took care of the problem for approx. 6 months. I now have a coolant leak that has no visible signs of the leak. The coolant level is getting worse loosing about 1/2 gal. a day with normal driving habits. The oil does not have any traces of coolant and the coolant reservoir does not have any traces of oil. The exhaust does not smoke or steam. Not sure what to look for, could this be the head gasket? Any help or ideas would be appreciated. Thank You!

05-03-09, 09:27 PM
Yes, it could be a head gasket. Northstars will rarely put coolant in the oil. The pipes will not steam in the early stages either. Best thing to do is have the coolant tested for exhaust gases or get a test kit from Napa and test it yourself.

05-04-09, 12:43 PM
Where is the leak coming from? Driver's side or passenger's side?

05-04-09, 05:14 PM
Thanks for the info, I will do a little more research regarding the possibility of the head gasket being the culprit. Again there are no visible signs of an external leak. What can I expect for a price range and difficulty for a head gasket replacement? Can a good back yard mechanic handle this job? Thank You for any information regarding this matter

05-04-09, 06:04 PM
Yes, a GOOD backyard mechanic can do it. Tateos has done it and can tell you more.

05-04-09, 08:30 PM
Thanks again Ranger. I have been looking at some other post in the forum related to head gasket replacement. This procedure can have many problems arise if not done correctly. Again Thanks for the assistance I will look into the possibility of my 1999 DeVille having a blown head gasket. Unfortunately at this time that appears to be the case. Thank You!

05-05-09, 09:49 PM
A blown HG will frequently evidence itself by blowing coolant out of the surge tank - on the passenger side on your car, I think.

05-17-09, 06:09 PM
Well I had the mechanic look at the car today to diagnose the issue with the coolant leak. Since the first post the car has started to run rough with a slight miss. The mechanic has told me that the miss is due to a bad spark plug wire. This is possible because the wire and plugs are original. On the coolant leak he says that #2 cylinder is the problem. Replace the head gaskets He wants to drill and tap the block and use larger grade #8 bolts and hardened washers. He has done one Northstar with this technique before with success. He says why put inserts in when the won't use a fraction of the bolts threads for holding power. What is your thoughts on this and do you have any pointers for the labor process and what to buy and or replace while doing the head gaskets? Thank You!

05-17-09, 08:38 PM
If you let him do it I would insist on inserts or Jake's stud kit unless he is going to warranty it for as long as you own the car.

He has done one Northstar with this technique before with success.
One? Not much of a track record. Define success? I know of a guy on the other Caddy board who did not Timesert (he didn't know any better), studs where not available then . He had success.......... for 10,000 miles. Then he did it again.

11-30-09, 05:26 PM
Ya i had this issue During the summer and it turned out yo be the water pump.

11-30-09, 05:50 PM
The OP had a blown head gasket on the front bank. Fixed 6 months ago. If your problem was the water pump, then it was leaking and losing coolant or overheating the engine and blowing coolant out the reservoir cap. The OP had no leaks.