: Zero Oil Pressure!! HELP!!



brad3378
06-26-04, 01:11 PM
1998 Deville Northstar 130,000 miles

I replaced both headgaskets so the oil pump was off to set the timing.
I hate to admit when I make a mistake, but the oil pressure was fine until I worked on it.
I have verified that there really is a low oil pressure condition with a handheld gage.


There is a bushing with 2 flat sides that fits between the Pump and the crankshaft. Here is what I don't understand: How does the bushing attach to the crankshaft snout? On the outside of the bushing there are 2 flat sides. On the surfaces where the crank & bushing mate, there are no splines, so I'm assuming there is supposed to be a press fit but the bushing spins freely on the crankshaft, so I'm not sure what's going on. My best guess is that I lost an important part somewhere in there.

I'm totally baffled!!!
I hope my pictures below help.

By the way, what is that odd keyway cut at a strange angle on the end of the crankshaft?


http://us.f1f.yahoofs.com/bc/3f8b6987_1868b/bc/cadillac/DCP_0017.jpg?bf.xf3AB6TbJASFG[/url]


[url="http://us.f1.yahoofs.com/users/f009524/bc/a448/__sr_/162d.jpg?phSGb3ABuK3Aopvc"] http://us.f1f.yahoofs.com/bc/3f8b6987_1868b/bc/cadillac/DCP_0020.jpg?bf.xf3AB0mWOm60W (http://us.f1.yahoofs.com/users/f009524/bc/a448/__sr_/26fb.jpg?phSGb3ABL8sOaGUY)

growe3
06-26-04, 07:50 PM
The "bushing" is the oil pump DRIVE SPACER. The two flats engage the inner gear of the oil pump. The Drive Spacer simply plips in place.

I believe the properly torqued vibration dampener is what locks it to the crankshaft to spin the inner gear.

For the 93' Northstar, yours should be the same, the dampener must be tightened down with 105 ft. lbs. of force.

Then mark the crankshaft bolt, not the washer, with chalk at one of the three spokes of the dampener. Rotate the chalk mark on the bolt 120 degrees to the next spoke, for its final tightened position.

-George

brad3378
06-27-04, 02:22 PM
Fixed!!!!!!!!!!

YAY!!!!

George - you were right on the money!!!
The Drive spacer is designed to be axially pinched between the shoulder on the crank snout and the harmonic balancer. I didn't find this very instinctive, but it fixed the problem and YOU probably saved my engine!

You guys are GREAT!!!!
You saved me A LOT of aggrevation -
3 cheers for George!!! :)

Thanks man!!!

CAJUN-Z
06-27-04, 07:07 PM
Since you seem to know about the Northstar engines, is there any truth that if you lost all coolant, you could still drive the vehicle for a number of miles without damage? Just curious if you heard something along those lines...

Ranger
06-27-04, 08:59 PM
Cajun,
Yes it is true. The Northstar is designed to run about 50 miles with no coolant. When the engine temp reaches about 260 degrees the PCM will go into the "limp home mode". It will alerternately shut down ijectors to 4 cylinders and use the intake air (without combustion) to help cool the engine.
(without engine damage)


Since you seem to know about the Northstar engines, is there any truth that if you lost all coolant, you could still drive the vehicle for a number of miles without damage? Just curious if you heard something along those lines...

BeelzeBob
06-27-04, 09:57 PM
George is correct in his explaination....but....that damper bolt takes a LOT more than 105 ft.lbs. .... Way more.... I would say that it takes closer to 300 ft. lbs. to get the correct tension on the damper bolt. 105 ft.lbs. is definitely way low and not nearly enough torque. The spec for the damper bolt is to first tighten the bolt to 37 ft.lb. then give it an additional 120 degrees of angle. This will take a lot of torque to go 120 degrees.


To make sure the damper is seated I would torque to the above spec, loosen the bolt and then retorque it.

Hopefully you pulled the damper on with a proper puller and did not pull it on with the production bolt. If you did the bolt may be damaged and it should removed and replaced. Pulling the damper on with the bolt will often stretch the end of the bolt or distort the end threads causing false torque readings and an improperly tensioned bolt.

BeelzeBob
06-27-04, 10:09 PM
Cajun,
Yes it is true. The Northstar is designed to run about 50 miles with no coolant. When the engine temp reaches about 260 degrees the PCM will go into the "limp home mode". It will alerternately shut down ijectors to 4 cylinders and use the intake air (without combustion) to help cool the engine.
(without engine damage)

Close.....

The limp home mode will automatically engage if the coolant temp sensor reads a temperature of 132 degrees C or about 270 degrees F. When the cylinder head goes dry (due to continued boiling or a catostrophic coolant loss) the coolant sensor in the cylinder head is influenced by the exhaust port wall temp and will rapidly reach 132 C and surpass the limp home threshold.

260 is hot...but not hot enough to enable the limp home. A 50/50 coolant mix at 14 PSI will not boil until 265 F....so 260 is not yet at boiling and well below the temp the cylinder head would reach even if wet and boiling.

Once the limp home mode engages the PCM automatically shuts off a group of 4 cylinders (1-7-4-6 or 2-3-5-8) by disabling the fuel injector. The dead cylinders pump air for a period of time and then that group of cylinders turns back on and the other group of cylinders is disabled to pump air and cool themselves)

The engine obviously runs rough and is way down on power but it can safely negotiate 50 miles like this with no engine damage to enable the driver to reach a safe place in the event of a catostrophic cooling system failure.

brad3378
06-27-04, 10:12 PM
It is DEFINITELY more than 105 foot lbs once you add that extra 120 Degrees. I'm guessing it's well over 300.


As a test to see if the Drive Spacer was being locked to the crankshaft, I reassembled without the oil pump and without the front cover.....
.... assembled with only the drive spacer and pulley.

The drive spacer was already too tight to turn by hand with only the initial 105 foot lbs. (I then removed the pulley and reassembled with the oil pump & front cover). The extra 120 degrees of torque is CRUCIAL and I admit I took a shortcut and assumed I could just put this back together (without torquing) with my 1/2 inch impact. Boy was I wrong!

I always find it hard to torque crankshaft pulleys because the crankshaft wants to spin and it's sometimes hard to hold the flywheel. A trick that I used this time was to hold the crank pulley with a cheap Coil spring compressor tool. One end hooked around the crank pulley while the other hooked arround the convieniently located front sway bar. It worked like a charm!

Thanks again to everybody!
Now I just gotta figure out my charging system and I'll be all set :)

BeelzeBob
06-27-04, 10:22 PM
If you pulled the damper on with the bolt and your impact the bolt is almost certainly distorted and should definitely be removed and replaced......


It is also easy to make a small tool that hooks to the teeth of the flexplate to hold the crank to keep it from turning.

brad3378
06-27-04, 10:32 PM
I appreciate the warning, but I'm safe this time (only because my regular puller was broken and had to borrow a tool)
I used a slide hammer with a 3 jaw attachment.

I'll tell ya man.......
......I sure can learn a lot from you guys!

BeelzeBob
06-27-04, 10:48 PM
A slide hammer....????....to remove/install a harmonic damper.


Now I will tell you that you need to replace the damper itself.


You should NEVER hammer or use any sort of impact load (like a slide hammer) to remove or install a harmonic damper. Axial hammer blows like that will destroy the elastomeric bond between the hub and the outer ring. The damper functions by having a center hub that is completely separate from the outer ring by an elastomeric layer that is designed to abosrb torsional vibrations in shear. Hammering or striking the damper axially will bread the outer ring loose from the hub and cause it to walk off the hub.


If you used a slide hammer on the damper I would strongly recommend replacing the damper at your earliest convenience. Otherwise the outer ring may just come adrift and sail thru the radiator...or worse.....


I thought that was the first lesson in autoshop 101.....never hammer on a harmonic damper.....

brad3378
06-27-04, 11:33 PM
Yeah - it wasn't my first choice to use a slide hammer, but I'm safe.

I attached a 3 jaw clamp to a slide hammer at the center hub of the harmonic balancer - there was definitely no stress put on the outer ring or elastomer material, although I admit I panicked and 2nd guessed myself when I got your response. I just came back from the garage with a giant sigh of relief when I double checked to see that the elastomer was at the outer perimeter of the damper.

Thanks again guys!

brad3378
06-27-04, 11:35 PM
by the way........the slide hammer did a lousy job compared to the traditional method of a puller. I just used what I had available since it's the weekend. :hide:

growe3
06-28-04, 08:15 AM
George is correct in his explaination....but....that damper bolt takes a LOT more than 105 ft.lbs. .... Way more.... I would say that it takes closer to 300 ft. lbs. to get the correct tension on the damper bolt. 105 ft.lbs. is definitely way low and not nearly enough torque. The spec for the damper bolt is to first tighten the bolt to 37 ft.lb. then give it an additional 120 degrees of angle. This will take a lot of torque to go 120 degrees.


Hi bbobynski,
According to my Helms service manual, Page 6A2-53, Bolt Torque Specifications; the Torsional Damper torques to 105 ft. lb. plus 120 degrees. I have bulit both of my engines with this spec and they are both working fine.

Is the manual in error?

-George

growe3
06-28-04, 08:17 AM
Brad, Glad to be of help.

-George

brad3378
06-28-04, 11:35 AM
The Manual is not in Error - I was.

I'm ashamed to admit that I only used my impact to tighten the
harmonic damper bolt because I was too lazy to do it by hand. I didn't believe that it was that critical until you guys explained how this is essentially what drives the oil pump.

My Chilton's Manual shows the same spec:
105 ft. Lbs plus 120 degrees.
I'm estimating that I only had about 100 ft lbs on mine, which I'm sure is way less than half of what's needed after you add that extra 120 degrees rotation.

BeelzeBob
06-28-04, 12:02 PM
The crank damper bolt changed over the years.....

The early engines had a much larger bolt in the crank damper which required the 105 ft.lb. of initial torque plus the 120 degrees of angle.

The 105 ft.lb.spec is good for the 93/94/95 engines I believe. Starting in 96 the crank damper bolt is much smaller and takes less initial torque before starting the 120 degrees. The spec for the 96 and later is the 37 ft.lb. plus 120 degrees becuase of the smaller diameter bolt.

George, I just wanted to make sure that your spec was not misread as "only" 105 ft.lbs. without the angle. The angle was covered in the next paragraph but it might have been missed if someone saw the spec of 105 ft.lb. (without the angle being called out) and stopped reading.

While much of the Northstar engine remained carryover over the years from 93-99 things like the crank damper bolt were changed so it is not a good idea to quote specs from different years of engines without knowing that the parts are the same. The manual is correct for the early engines that it was written for. My 96 manual is also correct for a 96 with 37 ft.lb. plus 120 degrees....

BeelzeBob
06-28-04, 12:08 PM
Yeah - it wasn't my first choice to use a slide hammer, but I'm safe.

I attached a 3 jaw clamp to a slide hammer at the center hub of the harmonic balancer - there was definitely no stress put on the outer ring or elastomer material, although I admit I panicked and 2nd guessed myself when I got your response. I just came back from the garage with a giant sigh of relief when I double checked to see that the elastomer was at the outer perimeter of the damper.

Thanks again guys!


Uh....NO YOU ARE NOT SAFE.

If you used a slide hammer on the hub OR the outer ring then the elastomeric bond in the damper is likely damaged and will fail. Putting the stress of an axial shock load onto the damper thru the hub or the outer ring is basically the same thing...it will fail the elastomeric bond. You have to apply a pretty good shock load to move the damper on a Northstar due to the press load of the damper hub onto the crank. That kind of shock load in an axial fashion will damage the elastomeric bond between the hub and the outer ring. Period. Seen it happen many times. Never Never Never hammer on a harmonic damper to install or remove it....Never. Yours should be replaced.

growe3
06-28-04, 03:22 PM
The crank damper bolt changed over the years.....

The early engines had a much larger bolt in the crank damper which required the 105 ft.lb. of initial torque plus the 120 degrees of angle.

The 105 ft.lb.spec is good for the 93/94/95 engines I believe. Starting in 96 the crank damper bolt is much smaller and takes less initial torque before starting the 120 degrees. The spec for the 96 and later is the 37 ft.lb. plus 120 degrees becuase of the smaller diameter bolt.

George, I just wanted to make sure that your spec was not misread as "only" 105 ft.lbs. without the angle. The angle was covered in the next paragraph but it might have been missed if someone saw the spec of 105 ft.lb. (without the angle being called out) and stopped reading.

While much of the Northstar engine remained carryover over the years from 93-99 things like the crank damper bolt were changed so it is not a good idea to quote specs from different years of engines without knowing that the parts are the same. The manual is correct for the early engines that it was written for. My 96 manual is also correct for a 96 with 37 ft.lb. plus 120 degrees....
Hi Bbobynski,
I noted the 120 degree additional rotation in my original note to Brad, but I was not aware of the difference in bolt diameters. Thanks :) for clearing up the difference between the years.

-George