: 97 Y NorthStar backfire



jwaynes
03-15-04, 11:39 PM
My 97 DeVille will backfire when starting if you don't crank the engine long enough.

Now, I have a blown head gasket.

Does anyone know if the two problems are related?
Is a backfiring problem common on the 97 Northstar engines?

eldorado1
03-16-04, 12:10 AM
I'm just gonna throw this out there... I'm not a ASE certified mechanic by any means, but I've worked on a few cars. It's possible that after the headgasket went, a cylinder filled up partially with coolant, and when you started it next, the timing chain jumped a notch. Cars do not backfire unless there is a problem with fuel getting into the intake manifold somehow, or the timing is off (either spark or valve).

Logandiagnostic
03-16-04, 12:34 AM
Are u sure your head gasket is blown? Hmmm

Backfires on the Northstars are often caused by a leaking fuel pressure regulator. Bad enough it can blow the intake safety valve.

Something to look at....

Logan
www.airbagcrash.com
www.logandiagnostic.com

jwaynes
03-16-04, 07:47 PM
It's possible that after the headgasket went....
It had the backfiring problem first. I bought the car in September of 2002 and it has always had a backfiring problem when starting if I release the starter too soon. The blown head gasket occurred in January 2004.

BeelzeBob
03-17-04, 04:17 PM
It had the backfiring problem first. I bought the car in September of 2002 and it has always had a backfiring problem when starting if I release the starter too soon. The blown head gasket occurred in January 2004.

"backfiring" has nothing to do with a blown head gasket..or vice versa. If you are thinking that the "backfire" caused the head gasket to blow then forget that idea. As loud as a "backfire" sounds it is nowhere near the pressure that is in the cylinder each time the spark plug ignites the mixture. A backfire will not blow a head gasket.

Usually, a repetative backfire is caused by a leaking fuel pressure regulator or a dripping/leaking injector. Not too difficult to diagnose. If it did it for that long why didn't you get it diagnosed and fixed instead of just letting it backfire that long....???

How do you know a head gasket is "blown" and/or what makes you think this? If it is blown I would doubt seriously that the two events are related.

jwaynes
03-17-04, 11:41 PM
If it did it for that long why didn't you get it diagnosed and fixed instead of just letting it backfire that long....???

How do you know a head gasket is "blown" and/or what makes you think this? If it is blown I would doubt seriously that the two events are related.
I didn't get it fixed right away because (1) I've been out of work and (2) didn't think it was harming anything.

The LasVegas dealer said a test of the radiator overflow for hydrocarbons showed I needed a head gasket replaced.

Lawrence
03-19-04, 12:32 PM
Are you loosing coolant? Or overheating?

BeelzeBob
03-19-04, 01:15 PM
I didn't get it fixed right away because (1) I've been out of work and (2) didn't think it was harming anything.

The LasVegas dealer said a test of the radiator overflow for hydrocarbons showed I needed a head gasket replaced.

Drain and refill the system with fresh DexCool to make sure the corrosion inhibitors are up to full strength in the coolant. When the system is drained disconnect the radiator hose and install 6 of the GM coolant supplement pellets/2 tubes of the BarsLeaks "golden seal" powder to make sure any incidental coolant seepages are sealed. Drive it and see how it acts.

Is the system overheating or something??? I assume there must have been some symptoms that caused the HC check of the coolant...???? That test is pretty inconclusive in my opinion so if that is the only thing indicating a "blown head gasket" I would ignore it.....

jwaynes
03-23-04, 10:40 PM
Is the system overheating or something??? I assume there must have been some symptoms that caused the HC check of the coolant...????
Bob and Lawrence, here is the chronology of the symptoms.

Sept 2002 - purchased the 97 Deville N* used with 111000 miles on the odometer.

June 2003 - drained, and refilled the coolant with DexCool. The local dealer said they don't put the sealant tablets in any more. However, I added 3 tablets, incorrectly in the overflow. (Doh!)

January 2004

Friday - driving from SLC UT to Las Vegas, the coolant low indicator came on. We were 180 miles from home and 180 miles from Las Vegas so we decided to go on with one eye on the temp. About 60 miles from Las Vegas the temp began to climb rapidly so we pulled off at the first exit and let the engine cool down. There were no signs of leaks. We topped off with water and grabbed a spare can with 5 gallon of water. We nursed the car into Las Vegas after several stops to top off the radiator. The last mile or so it went into overheat limp along mode.

Saturday - Called a local mech on wheels to check it out. He replaced the water pump and said it all checked out okay. Maintaining constant temperature for 45 minutes.

Sunday - Left Vegas for home. Got 20 miles out of town before it overheated. Spent 4 hours nursing it back into town. In the process, we changed the radiator cap and gutted the thermostat. Neither helped.

Monday - Las Vegas East Cadillac dealer diagnosed the system and said it was a blown head gasket because it showed hydrocarbons in the overflow. They quoted me $3900 to repair the head gaskets and probable head bolt problems. We gave up, flew home and later went back to tow it home.

March 2004 - Checked the bypass tube and it passes fluid. Also checked the tube going into the top of the overflow tank and it passes fluid easily. Drained the water and refilled with 50/50 cheap coolant. (If all goes well, I'll replace with DexCool.) Still have no thermostat. Drove 12 miles and the temp fluctuated from 190 to 212 once it warmed up. Need to try a little uphill drive and see how it reacts.

So, to answer your questions. Yes, it loses coolant through the overflow hose. And yes, it overheats in a rather odd way. Things all seem normal during warm up but when the engine is loaded such as going uphill and the temp climbs passed 220 then the temperature rockets on up to 260 and there isn't much you can do to stop it other than shutting down.

BeelzeBob
03-23-04, 11:00 PM
Bob and Lawrence, here is the chronology of the symptoms.

Sept 2002 - purchased the 97 Deville N* used with 111000 miles on the odometer.

June 2003 - drained, and refilled the coolant with DexCool. The local dealer said they don't put the sealant tablets in any more. However, I added 3 tablets, incorrectly in the overflow. (Doh!)

January 2004

Friday - driving from SLC UT to Las Vegas, the coolant low indicator came on. We were 180 miles from home and 180 miles from Las Vegas so we decided to go on with one eye on the temp. About 60 miles from Las Vegas the temp began to climb rapidly so we pulled off at the first exit and let the engine cool down. There were no signs of leaks. We topped off with water and grabbed a spare can with 5 gallon of water. We nursed the car into Las Vegas after several stops to top off the radiator. The last mile or so it went into overheat limp along mode.

Saturday - Called a local mech on wheels to check it out. He replaced the water pump and said it all checked out okay. Maintaining constant temperature for 45 minutes.

Sunday - Left Vegas for home. Got 20 miles out of town before it overheated. Spent 4 hours nursing it back into town. In the process, we changed the radiator cap and gutted the thermostat. Neither helped.

Monday - Las Vegas East Cadillac dealer diagnosed the system and said it was a blown head gasket because it showed hydrocarbons in the overflow. They quoted me $3900 to repair the head gaskets and probable head bolt problems. We gave up, flew home and later went back to tow it home.

March 2004 - Checked the bypass tube and it passes fluid. Also checked the tube going into the top of the overflow tank and it passes fluid easily. Drained the water and refilled with 50/50 cheap coolant. (If all goes well, I'll replace with DexCool.) Still have no thermostat. Drove 12 miles and the temp fluctuated from 190 to 212 once it warmed up. Need to try a little uphill drive and see how it reacts.

So, to answer your questions. Yes, it loses coolant through the overflow hose. And yes, it overheats in a rather odd way. Things all seem normal during warm up but when the engine is loaded such as going uphill and the temp climbs passed 220 then the temperature rockets on up to 260 and there isn't much you can do to stop it other than shutting down.

First thing is to PUT THE THERMOSTAT BACK IN. The Northstar uses an inlet side stat the also controls the bypass flow inside the water crossover and the block. Without the stat in place and operating correctly the system will not cool the engine and any results are inconclusive.

Now that you put the "cheap" coolant into the sytem (I assume you mean the green, silicated coolant) there is little or no point in returning to the DexCool. The system will be contaminate with silicates from the green coolant and the long life feature of the DexCool (which is what DexCool is all about....) is rendered moot. So, just keep on using the green coolant and change it frequently...you'll have to change the DexCool anyway as it will not last very long with the silicate contamination.

I would dose the system with the Gm coolant supplement heavily to make sure that there is no internal leak somewhere. Put at least 6 of the GM coolant supplement pellets or 2 tubes of the BarsLeaks "golden seal" powder into the RADIATOR HOSE this time. Putting it into the pressurized surge tank is useless.

Double check that the water pump drive belt is good and that the tensioner on the water pump drive belt is tensioning the belt and not stuck. Replace the radiator cap with a new or known good one. Make sure it is the correct one for the Northstar engine...there are different types of radiator/pressure caps. If the cap is not sealing or is failed the system can boil prematurely.