cylinder heads

[turk1124]

i have a 98 deville that i think has bad head gaskets on the 4.6 northstar, what i need to know is if it is possible to remove the heads with the engine in the car, and if there are any suggesstions on the procedures to change the gaskets?

[KHE]

If you have a '91 DeVille, you have the 4.9 engine, not the Northstar. Head gaskets are a very rare failure in the 4.9 engine. A much more likely suspect is the intake manifold gasket which can be replaced with the engine in the car.

What are the symptoms?

[turk1124]

If you have a '91 DeVille, you have the 4.9 engine, not the Northstar. Head gaskets are a very rare failure in the 4.9 engine. A much more likely suspect is the intake manifold gasket which can be replaced with the engine in the car.

What are the symptoms?

sorry , i missed the proper year , it is a 98, the symptoms are that it runs normally during normal driving, the temp runs between 198 degrees up to about 223, then the fans kick in and cools back to 198, but if you drive it on the highway pulling a hill , the temp rises to about 250, then comes back down after you crest the hill also , when the temp rises to 250, it starts blowing out the rad cap, . the systems been flushed, thermostat changed, water pump changed, and made sure the antifreeze(dex-cool) was at the proper mixture and at the right level, pressure checked the system for leaks, what is the proper system pressure ?

[JimD]

Your maximum pressure will be 16 psi. As in the cap will start to relieve pressure at 16 psi.

There are several more tests before you condemn the head gaskets.

Are you losing coolant other than the amount that spills out when the cap relieves pressure?

Test the coolant for presence of exhaust gases; DIY with test strips or have a radiator shop test it for you. Not 100% accurate.

Do a cylinder leak test with shop air through each spark hole while you listen for bubbling in the cooling system. Closer to 100% accurate.

The easiest way to repair head gaskets (if that turns out to be your problem) is to drop the engine cradle. Folks have done them with the engine in the car, but the right bank (firewall) is a back breaker to get to.

[zonie77]

Have a radiator shop do an exhaust gas (combustion byproduct) test on the coolant. Rad shop is usually MUCH faster and cheaper than having a mechanic do it.

If it's positive then you know it's HG's. Negative and you can pursue normal overheating fixes.

As scary as dropping the cradle looks it is not that bad and can be done using an engine hoist to raise the body. Once the cradle is out everything is easier to get to.

Here's some more info:

http://www.cadillacforums.com/forums/cadil...?highlight=5052

[Bruce Nunnally]

photo essay here on Caddyinfo showing head gasket repair with the engine out of the Cadillac:

http://www.caddyinfo.com/howto/nsrepair.htm

Lots of discussion can be found also using the 'search' to the upper right.

[Ranger]

Don't forget to check the purge line to be sure it is clear and flows coolant.

[BigCat83]

I finished Timeserting the block in my '97 Eldorado a coupla months ago. I dropped the cradle onto 4 jack stands, raised the front of the body with my engine hoist and "had at it". Car runs better now than it has in a long time. A real PIA but it can be done.

[turk1124]

Have a radiator shop do an exhaust gas (combustion byproduct) test on the coolant. Rad shop is usually MUCH faster and cheaper than having a mechanic do it.

If it's positive then you know it's HG's. Negative and you can pursue normal overheating fixes.

As scary as dropping the cradle looks it is not that bad and can be done using an engine hoist to raise the body. Once the cradle is out everything is easier to get to.

Here's some more info:

http://www.cadillacforums.com/forums/cadil...?highlight=5052

Have a radiator shop do an exhaust gas (combustion byproduct) test on the coolant. Rad shop is usually MUCH faster and cheaper than having a mechanic do it.

If it's positive then you know it's HG's. Negative and you can pursue normal overheating fixes.

As scary as dropping the cradle looks it is not that bad and can be done using an engine hoist to raise the body. Once the cradle is out everything is easier to get to.

Here's some more info:

http://www.cadillacforums.com/forums/cadil...?highlight=5052

thanks for the info so far , now i have another question, i have a factory manual on the way ,but until it gets here , what i have run into now is that im almost ready to drop the engine cradle , but i also have the abs module thats bolteded to the cradle also , do i have to dissconnect the abs, or will the module stay in place and hang there while the cradle is lowered?

[KHE]

With the engine cold, disconnect the purge line from the surge tank (it's the line that goes to the thermostat housing by way of the throttle body circuit. Have a helper start the engine and verify that coolant flows out the hose. If not, then you've found the problem.

Dropping the cradle may be premature without performing the troubleshooting techniques mentioned by others in this thread.

[zonie77]

Dropping the cradle may be premature without performing the troubleshooting techniques mentioned by others in this thread.

KHE is correct, have you had the combustion byproduct test done??

You can drop the cradle without disconnecting the brakes. (At least on a Seville) Everything stays with the body...the calipers hang from the fenderwells. Did you read the links?