Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

Ims advice please and help

Can only be done with your gearbox & clutch off but with engine in. Just wait till you have access there for a clutch, etc.
 
alex yates said:
Can only be done with your gearbox & clutch off but with engine in. Just wait till you have access there for a clutch, etc.
Thanks, Alex. As it's only done 30k I think a new clutch is some way off.
 
1st new clutch on mine was around 40k.
 
alex yates said:
1st new clutch on mine was around 40k.
About two years to go for me then :D
 
Hooner said:
my car i a 99 3.4 which has the dual row bearing now clocking on 100k the rms is leaking so in the winter i am thinking of changing it, if the ims looks dodgy what could i replace it with? as the dual bearings are no longer available.

You can fit a standard single row bearing and make up a spacer athough I like the look of this dual row bearing which should be better (although maybe not as good as the original dual row bearing :dont know: I've not heard of anyone fitting it so I think you should be the guinea pig).

https://www.onlinebearings.co.uk/32...ular-Contact-Ball-Bearing-Polyamide-Cage.html
 
The difficulty here is that some bearings were fitted a bit tighter than others (usual manufacturers tolerance build up) and these generated more minute running in metallic particles that mixed with grease and formed grinding paste that prematurely damaged some bearings.

Most however were OK.

The grease gradually escaped because when hot it is very thin and at that point it depends how worn the seal is as to how much engine oil can seep back in to protect the bearing.

This is why they either seem to fail early (under 45K) or last well over 100K.

Unfortunately the small spindle shaft that holds it all together has a machined recess in it for an "O" ring and this makes it weak in bending.

When you remove the spider to inspect or remove and replace the bearing - even with the chain tensioners removed at the right crankshaft angle to avoid chain timing slip - the tension in the chain makes the bearing sit out of line with the hole it has to fit into and the sideways pressure needed to align it is often applied by bending loads on that weak spindle making it likely to metal fatigue in the future.

Furthermore the bearing hole will have picked up metallic deposits (compaction) so after removing the old bearing it may not be perfectly round so this needs inspecting and measuring before a re-fit and if unsuitable remedial work may be needed.

Because most early failures have already occurred by now and because it can do more damage by trying to replace a bearing - the statistics show absolutely that leaving it alone is p roving a cheaper option than trying to replace it in situ.

This will of course not stop a small number of unfortunate owners still having a failure but it is better overall for us to give advice that applies to and benefits the vast majority than that which would make more of them suffer as a result.

The bearing size of the small bearing is basically to small for the job and whether it is a single or double ball bearing, or a roller bearing (that will not resists the significant side loading that chain flap causes) the only reliable alternative to fit in situ is a solid bearing with separate oil supply.

Since many engines will need a rebuild at higher mileages and we can then fit the larger bearing (without seal) either a Porsche one or our own remanufactured version (which is made with both Hivo and roller chain drives so suits older cars as well) this adds to the advice that generally and statistically it might be better to leave alone than try and inspect it (unless there are obvious signs of failure of course).

If there are obvious signs that something needs to be done and the owner cannot afford an engine rebuild then the risk of replacing the bearing in situ has to be born and in those cases we have an alternative available.

We have had to replace many other "replacement" designs that had grand claims associated with them but never a solid bearing version (although they are much more expensive).

It is sad that less help was not forthcoming from Porsche and the many independents that have tried their best in good faith to provide a solution should not be berated if they do not always work as well as they hoped. If Porsche could not get it right it is a bit much to expect small independents to.

A single bearing has just as much load rating as a double row because the internal tracks are narrower in a double row and so either are similar in rating.

There are different ball bearing types and suppliers and they come in different specifications and tolerances and the right one to use relates to the original clearances and tolerances Porsche made the parts to and should allow for age deformation of the bearing housing and compaction etc.

My own personal view is that with all older Porsche's following the traditional trend of eventually increasing in value and with less petrol sports cars likely to be around in years to come and with properly rebuilt engines (and properly designed and developed oversized versions becoming available) it might be better to consider that route and fix the IMS problem at the same time and for posterity.

Sorry to repeat that none of this advice will prevent some poor soul somewhere having a failure - it is a small risk factor that was not caused by the independents and there are plenty of alternatives to consider.

Sorry there is not a simple solution.

Baz
 
Excellent post Baz - I think we all appreciate your input.

I for one am following your advice (am on 80k and original IMS - as far as I know). I accept the risk (small) I am running, based on the statistics.
 
I have gotten hold of a nos double row ims bearing and am wondering if there is a stronger shaft it sits on available any where? or a new one incase it breaks whilst trying to remove it. :?:
 
You must be crackers removing a good bearimg and fitting an unknown dual row. The failures were mainly due to bearing tolerances. You NOS bearing may be one of the ones that go pop.
 
alex yates said:
You must be crackers removing a good bearimg and fitting an unknown dual row. The failures were mainly due to bearing tolerances. You NOS bearing may be one of the ones that go pop.

im not removing it yet, i'm gathering parts for a future overall the new on will be fitted without the oil seals if and when required. I new stronger retaining shaft would be fitted too if i can locate one?
 
Hooner said:
alex yates said:
You must be crackers removing a good bearimg and fitting an unknown dual row. The failures were mainly due to bearing tolerances. You NOS bearing may be one of the ones that go pop.

im not removing it yet, i'm gathering parts for a future overall the new on will be fitted without the oil seals if and when required. I new stronger retaining shaft would be fitted too if i can locate one?

Have to agree with Alex here - did you read Baz's point below?

The bearing size of the small bearing is basically to small for the job and whether it is a single or double ball bearing, or a roller bearing (that will not resists the significant side loading that chain flap causes) the only reliable alternative to fit in situ is a solid bearing with separate oil supply.
 
Still crackers fitting a bearing with a known manufacturing defect when the one already in is fine.
 
If you are doing an engine rebuild, go for the larger bearing option Hartech offer.
 
Baz states that the retaining shafts are weak due to the oil seal in it, and can snap or fracture on removing them is a new one available? the new bearing without the seals no doubt will be fine as we know failures of these are quite rare.
 
To quote:

bazhart said:
The difficulty here is that some bearings were fitted a bit tighter than others (usual manufacturers tolerance build up) and these generated more minute running in metallic particles that mixed with grease and formed grinding paste that prematurely damaged some bearings.

This is why they either seem to fail early (under 45K) or last well over 100K.

Baz

Fitting a NOS sticks you right in the middle of this ball(bearing) park.
 

New Threads

Forum statistics

Threads
124,354
Messages
1,439,461
Members
48,713
Latest member
3sp1f8
Back
Top