IMS bearing change question

[harmonyroadporsche]

When doing the IMS replacement procedure is it OK to completely remove the Main and 1-3 tensioners? I've read that you should just loosen them but I've also heard that you should remove them. Also, is loosening or removing the 4-6 tensioner necessary? Since the engine is coming out and the AC compressor will be out of the way it is easy to access it however if it isn't necessary to remove it I'd rather leave it alone. Thanks in advance for any advice you can give me.

Thanks!

J

[j_beede]

Are you replacing your IMS bearing with the factory part, or upgrading to a non-sealed bearing?

...j

[logray]

The answer is it depends on the year.

5 chain models you can get away with just REMOVING the main IMS tensioner and the 1-3 tensioner. Locking the cams is recommended but the procedure can be successful without. Removing 4-6 tensioner is also recommended, however the procedure can be successful without doing this.

With 3 chain models, you want to lock the cams in place with a lock tool, and have as much insurance as possible, including loosening or removing the tensioner.

ON a different note, Wayne at pelican has pioneered and ingenious method of doing this which doesn't require locking cams, and just using a set screws in place of the IMS flange bolts to pin the ims so it won't move.

Loosening the tensioners is also talked about in some DIYs and some have had success with doing this, however IIRC the "official" procedure is to remove them completely.

As always, after performing an IMS retrofit, verifying timing is highly recommended and cheap and easy insurance (new cam caps) to validate the car won't explodo when you starto.

Edited June 29, 2011 by logray

[harmonyroadporsche]

I will be upgrading to the non-sealed bearing using the LN kit.

Since the LN kit comes with the two fly wheel locks I'll go with that method and I'll remove all three tensioners to be safe. It would be nice if I could lock the IMS sprocket with the set screws as well but that may not be possible at TDC. Do you remove the tensioners in a particular order starting the with the Main and following with 1-3 and 4-6? Do you know what the tightening torque is when reinstalling the tensioners?

[logray]

...Since the LN kit comes with the two fly wheel locks I'll go with that method and I'll remove all three tensioners to be safe. It would be nice if I could lock the IMS sprocket with the set screws as well but that may not be possible at TDC. Do you remove the tensioners in a particular order starting the with the Main and following with 1-3 and 4-6? Do you know what the tightening torque is when reinstalling the tensioners?

Good choice to be safe as possible. If you didn't follow those steps and a chain skipped, which is more common on 3 chain cars - it would mean a lot more dis assembly to get it right again (cam covers, etc.).

Wayne's pionneering approach actually has you perform the procedure with the engine NOT at TDC. However if you are using the cam locks then I would advise you to follow the LN procedure.

You can find out more information about the procedure from his write up. It is a good read.

http://www.pelicanparts.com/techarticles/Boxster_Tech/14-ENGINE-Intermediate_Shaft_Bearing/14-ENGINE-Intermediate_Shaft_Bearing.htm

As per the procedure, you should relieve tension on the camshaft chain tensioners before loosening the IMS tensioner.

The torque value for the tensioners is 59 ft lbs.

[harmonyroadporsche]

I had previously read Wayne's IMS article. It looks like he's updated it in the last few days as it now says the tensioners should be removed completely versus loosened.

So the loosening should be:

1-3 camshaft tensioner

4-6 camshaft tensioner (optional on 5 chain engines - 2002 or earlier)

Main IMS tensioner

Tightening the above tensioners in reverse order to 59 ft-lb (80 Nm) after the bearing and bearing cover are back in place. Tighten the bearing cover bolts down to 8 ft-lbs (11 Nm). And then torque down the 12 point nut to 24 ft-lbs (32.5 Nm). Button the whole thing up, check timing to ensure no valve on piston contact and then drive with confidence.

Thanks for your help!

[logray]

Yep, you've got it right.

For what it's worth, I don't think the order of 1-3 or 4-6 tensioner matters if you are going to do both, but 1-3 is certainly easier to access and is a must since it's on the flywheel side where the bearing is.

The revised 4-6 tensioner under the A/C has an allen head and if I remember right can be loosened and possibly removed from at least the threads with a long hex driver and likely without removing the A/C.

Also check to make sure the new IMS flange doesn't contact the flywheel teeth.