: Problems with N* motor

07-23-07, 01:09 PM
Hello i am new to this forum and drive a Seville with N* Motor (240000 kilometers). I am from Germany and so you have to apologize my poor grammar :-)
I recognized a high oil consumption (2/L on 1000km) , very poor fuel economy (40/L on 230km) and a lot of blue smoke out of the exhaust when i start my car or kicking the gas pedal to the bottom, so i took my car to service.My first idea was that the cylinder head gasket needs to be repaired. After a compression test the result was that at cylinder no. 7 was no/very little compression but all other cylinders have values within the tolerance. I have read some time ago about a leak down test in this forum,...so i have just tried to find some car service point who will make a leak down test. Its really hard to find in Germany somebody who have ever heared of of a "leak down test". All mechanics wanted to make a compression test and i have to explain how a leak down test will made. After that most of them said sorry we cannot make this. At last i found someone who make a leak-down-test to check if the cylinder head gasket is not working( i have expected to hear some bubbling water if cylinder head gasket ist blown),....but no noise in the cooling water. The mechanic said that low compression can caused by not correct working exhaust valves (he said that they maybe not close tightly).
Could this be the reason for the sympthoms? Is it possible to change these valves without unmounting the whole motor with transmission?
I would be very glad if someone can give me some hints ,.....its really very difficult to get qualified mechanics in germany which can repair us-cars. I asked at cadillac europe and they said : " A repair of this motor is not possible (at a normal price) , what about buyin a new cadillac? "
At least i found a mechanic who will try to fix the problem , but he is only experienced with modells of chrysler , so he will need a lot of hints ;-)

07-23-07, 02:02 PM
Blue smoke and oil consumption is not likely a head gasket. We rarely hear of valve problems either. I would guess that you are suffering from stuck rings. Go to the top left of this page and click on the Technical Archives. Read up on "Full Throttle Acceleration" aka WOT (Wide Open Throttle) and Northstar Oil Consumption. You may find your cure there. It is cheap and fun. Best of luck and keep us updated.

07-23-07, 02:37 PM
I agree -- the problem appears to be piston ring-related, especially if it's just one cylinder and the car doesn't otherwise use any coolant.

07-23-07, 07:56 PM
Kingbruce, it appears you are all by yourself with your Cadillac / Northstar engine.

May I strongly suggest you buy the complete Factory service manuals?

They are 2 "telephone book" sized books that can help you, and your local friendly mechanic.

I replaced my Northstar engine all by myself using these books. They also tell you everything you need to know about your car.

They are about $80.00 US dollars. Worth every penny.

07-23-07, 09:04 PM
You can do the cylinder pressure test by making an adapter from an old spark plug or a compression tester plug. You put at least 100psi air pressure into each cylinder with the piston at TDC and the valves closed. If you get bubbles or movement in the coolant you know the HG's are bad. If you have bad valves you will hear the leakage either into the intake manifold or exhaust pipe. If the piston rings are stuck you will hear the leakage at the oil fill opening.

Here's a link with info on doing the HG repair. Show it to your mechanic.


There is no part 2...

08-14-07, 05:15 AM
Thank you all very much for tipps and hints,....
The new mechanic is trying to open the engine without unmounting the whole engine/transmission. Bu it seems it is not possible to reach every screw when the engine is still installed (there are some metal pipes in the back part which are running over the screws wich had to be opened. :rant2:
The price of unmounting everything and buy the needed parts + labour would be around 4000$ :eek:
These costs are definitly toooooo much ,.....(i am still a student)
I think i will try some WOTīs and if this does not help i have to sell my car. My heart is bleeding but there is nothing else to do.

08-15-07, 03:42 PM
Update: The "new" mechanic in the service point said that is impossible/too much work to take the engine out. He also said that a lot of special tools are needed like a tool to disconnect the fuel pipes and he have none. Can somebody give me a list which "special" tools are needed to unmount a N*? Also some www adresses where to get the parts? We also had a funny discussion with him. He said it is impossible to open the rear valve cover when the engine is still in the car. My opinion was it is possible. So i pulled of my jacket got some tools and after 3 hours of work and 5 broken fingers :-) i got all screws for the rear-cover off. Funny was that it was still not possible to take cover off because i could not lift the cover high enough :-(
Tommorow i will mount on all engine parts again and will search for a new service point (the next one will be the 4th i think). I would be very glad if someone could say me which tools are needed. Thx @ all

09-22-07, 03:37 PM
Update: Now my Caddy is running fine. At least i found a mechanik who located the problem and fixed it. It was a burned exhaust valve. I think i am the first User in this Forum who had this problem :)
Here a picture of the burned valve and its neigbhour:
http://www.abload.de/thumb/pic02890x2t.jpg (http://www.abload.de/image.php?img=pic02890x2t.jpg)

But after the reapair my cruise control isnt working any more. Do someone have Ideas what can cause this? I think its possible that the mecanic has forgotten to plug a switch in the right place. Does anyone know where the "plugs" for cruise control are located?

Thanks for your help

09-22-07, 04:23 PM
Holy burnt valve Batman! Never seen that before. Any idea what caused it?

Does anyone know where the "plugs" for cruise control are located?
Model & year?

09-22-07, 04:28 PM
Holy burnt valve Batman! Never seen that before. Any idea what caused it?

As far as the burnt valve, something held it off the seat. Could be slightly
bent or stuck in the guide from sitting. Once its off the seat it can't
transfer heat and starts to burn like it has a torch on it.

09-23-07, 06:01 AM
Holy burnt valve Batman! Never seen that before. Any idea what caused it?

Model & year?

Itīs a 96 Seville STS. No errors on Onboard diagnostics expect TC0045 & PC1520. The TC Code is caused by a bad ABS Sensor on front right. No idea why a PC1520 is stored (car is still shifting very smooth).

09-24-07, 02:44 AM
Looks like debris got into it while it closed. They don't usually burn that deeply otherwise, usually more following the circular shape of the valve.

09-24-07, 07:24 AM
Is this a 99 and prior car?
What number cylinder are the valves from?

09-24-07, 06:17 PM
@AJxtcman: It was cylinder no 7. By the way the car is from 1996 with 240K Kilometers on it.