Northstar Coolant Loss

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Northstar Coolant Loss

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Cadillac >> General Technical Section >> Engine Specific >> Aluminum Block V8s >> Northstar Coolant Loss

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Northstar Coolant Loss - 5/22/2007 3:35:01 PM

dyates773

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Many thanks to all of you who have repeatibly posted your comments on the well known issue of Northstar headbolts losing thread integrity in the block leading to head gasket issues. I own a 1998 Seville STS with 194,000 miles. The car is in excellent condition except...... at sustained highway speeds the coolant is forced out of the coolant tank cap. The car will overheat when the level drops enough to stop flowing or gets "air bound". This car is in good enough condition to drive everyday, runs great, but cannot be driven at sustained speeds over 60 mph. Its age and condition does not warrant installing a long block or a major teardown on such a high mileage engine, the cost alone would be more than the car is worth. For those of you in my situation I have engineered a less than perfect but workable solution. My thinking was how to vent the exhaust gas and pressure to prevent forcing out the coolant. Being a Chemical Engineer I'm very familar with industrial hot water systems. Many of these systems cannot tolerate air in the piping. Most of them have air vents in the piping system. They are high pressure and high temperature. I have installed a 1/2" NPT float type air vent into one of the cooling system bypass hoses that now vents the trapped combustion gases. The vent is rated at 50 PSI and 250'F. It has worked for over 1000 miles in the last month. It does not pass liquid, only air. Today I drove home on the Interstate at 70MPH for over 40 miles with an outside temperature over 80 degrees. No overheating. I will post a picture if there is any interest. Good luck.

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RE: Northstar Coolant Loss - 5/22/2007 3:57:18 PM

Stealth

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PLEASE .... POST the pictures, all you got.
this is a huge problem going by the number of complaints on this site alone.

thanks

(in reply to dyates773)

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RE: Northstar Coolant Loss - 5/23/2007 2:59:28 PM

FLCaddytech

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quote:

at sustained highway speeds the coolant is forced out of the coolant tank cap. The car will overheat when the level drops enough to stop flowing or gets "air bound".

This does not seem like the typical head bolt issue.
Usually the engine will overtemp without even being low on coolant and no visible signs of coolant loss are evident.

I would suspect a faulty cap if coolant is being lost from the reservoir before the engine overheats.
Also cracks in the reservoir have been found from time to time causing a leak in that area.

I'm not trying to take away from your possible bandaid but the head bolt issue if let go will lead to eventual gasket failure.

(in reply to Stealth)

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RE: Northstar Coolant Loss - 5/23/2007 4:25:48 PM

dyates773

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I've attached a couple pictures. As I stated in my initial post this is not a perfect solution but will keep my car driveable for I hope a good period of time. I'm assuming gasket failure is in my future but this is a third car for the wife and I and I love it.

I would recommend anyone who trys this to be creative. I tapped into the coolant port on the thermostat housing out of convenience. There may be a better location.

Any hot water system air vent will most likely work if you pay attention to size, pressure rating, and temperature rating. The unit I used in the picture came out of the scrap metal bin at work and all I did was clean it and paint it. They are simple devices. I recommend a float type air vent.

I'll help anyone who is interested in extendeding the life of their engine.

Attachment (1)

(in reply to Stealth)

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RE: Northstar Coolant Loss - 5/23/2007 4:33:46 PM

dyates773

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An additional comment. I agree that the engine can overheat without coolant loss. The very first time my car overheated I saw the antifreeze all around the tank and immediately changed the cap. The next time it got hot there was no fluid loss but the tank was completely full. High temperature without loss of coolant in my opinion is caused by loss of flow due to the high pressure gas bubble in the coolant system., what I call being "airbound".

Attachment (1)

(in reply to FLCaddytech)

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RE: Northstar Coolant Loss - 6/22/2007 9:32:51 AM

Stealth

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dyates,

any gas/air in the sytem can cavitate the pump and stop flow.
if you keep getting gas/air, i can only think of one reason.

i looked at your pic and not sure i know what i am looking at,
i wil revisit later when i got mroe time.

for cars that arent worth the cost of a teardown, do consider the resin solution
that others have used. it seems to work in most every car. it extends the life of
the engine when the issue is the headgaskets.

keep us posted ....

< Message edited by Stealth -- 6/23/2007 11:11:21 PM >

Post #: 6