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Discussion Starter · #1 ·
I'm working with my brother on his 1997 Caddy DeVille Concours. It has the 300 HP Northstar engine. It consumes coolant without any apparent leaks. I read that these engines blow head gaskets and the coolant is forced out of the engine. We did a compression check on the easy cylinders 2, 4, 6, 8. Cylinders 2 and 8 are approximately 120lbs. Cylinders 4 and 6 are near 100lbs. Does anyone know what the healthy pressure should be. This engine has approximately 135,000 miles on it. The car is in very good shape and we would like to repair it. Thanks.
 

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I don't know what the pressures should be, but a good rule of thumb is if the pressures are within roughly 10% of each other, they are OK. Now you need to go check that other side.

BTW - is there white smoke coming out of the exhaust? Does the oil/coolant look normal? Two other things to check if you suspect coolant is going where it shouldn't be.
 

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If you have a 1997 Northstar that's consuming coolant you have a head gasket problem.. No iffs ands or butts.

You can do a test for exhaust gas in the coolant... But sadly it will come back positive.

GM has some issues with the 1997/98 & 99 Northstars and their head gaskets.

The really bad news is that the way this engine is packaged in the car you need to LIFT THE CAR off of the engine.

How to do this is documented here:
Link to timesert job

and here (also with pictures)
Link 2

As you will note, GM used similar bolts in the 97/98/99 Northstar as they did in the Quad 4... Sadly they have proven to be too short with too fine a pitch. When they are removed they will damage the block to a point where the block will not hold the replacement bolts.

You need to get either a TIMESERT kit or a NORMSERT kit
THESE ARE THE ONLY ONES THAT WILL HOLD
Helicoils or other insert will not hold for any length of time

(BTW GM sorta fixed this in 2000 with longer head bolts... and then made the fix permanent in 2004 with new head bolts that are similar to the LS1/2 engine)

The good news is that if you have the tools and the skills to do this... This can and has been done by several DIY types for <$1000 (in tools and parts)
The Timesert kit will cost about $400 new (cheaper on ebay) and you should replace the water pump, the motor mounts and reseal the bottom end of the motor while it is all apart.

Good Luck
 

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Discussion Starter · #4 ·
Thanks, I think you have confirmed what we were thinking. There has been the smell of coolant coming from the exhaust but other than that no trace of leaking. We have already replaced the water pump, radiator and the radiator cap. The repair looks like a chore of a job.
 

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Yup...

Most dealers will charge between $4,000 and $5,000 depending on their "door rate"
 

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No problem..

On issue you need to watch for... When you drill out the threads for the Timeserts (or Norm's inserts) you need to get "good" metal chips... Nice strong shinny ones... If the come out in a grey power the block is toast. Unfortunaly from what I hear you have a 50/50 chance that the block will produce "powder"...

AND BEWARD of 97-99 wrecker NorthStars... make sure you see the car that the engine comes out of... If there is no collision damage then you can be sure you are buying an engine out of a car that went to the wrecker because they wouldn't pay the dealer $4,000 to fix the blown engine...

Link to Norm Inserts

You might want to investigate "Norm Inserts" (link above) they are apparently stronger and cheaper then Timeserts...

And one last thought... The lastest trend is to use 2004 and newer inserts (and head bolts) in the 1997-99 blocks... The bolts are longer, stronger and have a better pitch for aluminum blocks...

You'll find all about this at
http://www.cadillacforums.com
 

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i have a 99 sts.. i bought in knowing the headsgaskets needed to be done and soon found out why everyone says these things are a nightmare.. i read that using inserts instead of helis was the way to go.. unfortunatly the timesert kit is 500bucks plus another thirty or so for the extra inserts.. i would need to get them shipped from arizona off ebay bc of the very rare thread pattern 11m x 1.5,that these come with (no wonder most ppl take them to gm and pay the ridulous 150 or so an hour for them to do the work ) . however i found that there is STUDS that arent listed as caddy parts but are the same thread pattern they are a vw stud but will work on one condition. u must take them to a good machinest and add an extra 35mm of lenghth to the studs. or call apr and ask if they can customize it. I was than able to use the cheaper but still rare 11m x 1.5heli coils, by the time i was done with the helis i found out i should of gone with the much easier to install timeserts, the helis will work with STUDS not bolts. but the time it takes to install the cheaper helis, wich are faaaar more difficult and finniky to install, i should have just bought the timesert kit, and make it that much more reliable.. oh well hinesight i guess.. it has been a time consuming fix to say the least.. but if you learn from my mistakes and by the timerts with the studs instead of bolts just to make it that much stronger, and follow these steps.. 1. get your studs threaded so total thread is 49 or 50mm deep 2. make sure you use timerts and install them CORRECTLY. 3. check your block to make sure your drill shavings arent powedery. u will save sum more time than i did, and you should have a good fix.! GOOD LUCK STAY CALM!LOL
 
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