Big end bearings replacement

[itchyfeet]

Although they do specify that it's particularly good for measuring large bearings such as in marine applications.

Anybody know whats acceptable for crank to rod bearing clearance?
Can't see anything in bentley.

Looking at this thread from an Aircooled....0.15mm sounds alot?

http://www.volkszone.co.uk/VZi/showthread.php?p=8928666" onclick="window.open(this.href);return false;

Radial wear is the other thing referred to - that I'm guessing that means actual movement between the big end bearing and the crankshaft - so movement in line with the conn rod - and the target for a new part is stated as .0008" to .0027" (0.02mm to 0.07mm) and a wear limit of .006" (0.15mm).
By hand, I can feel no movement in line with the conn rod.

[Mr Bean]

Just bare in mind that at these comparatively close fits any residual cold oil will act as a damper and will need considerable force to displace. Plus the width to diameter ratio of the journal necessitates that the rod be held at perfect right angle to the crank pin axis. Nonetheless this is viable test.
CS

[itchyfeet]

Any test needs pass of fail limits or it's pointless, we don't have them?

[Mohamster]

Any test needs pass of fail limits or it's pointless, we don't have them?

From watching this video it seems that Plastiguage can be used to test against defined wear limits ...

https://www.youtube.com/watch?v=q3pHb-qXZc8" onclick="window.open(this.href);return false;

Just bare in mind that at these comparatively close fits any residual cold oil will act as a damper and will need considerable force to displace. Plus the width to diameter ratio of the journal necessitates that the rod be held at perfect right angle to the crank pin axis. Nonetheless this is viable test.

Just to add, also something I learnt from the video, it needs to be done at room temperature in order for the result of the material compression to be comparable to the reference card.

I'm not replacing no bearings this time around though .. instead I've bought an oil guage and will use that to monitor wear and to therefore plan another engine removal. That said I will definitely do what Itchy, and others it seems, suggest and find a spare engine to build up so as to minimise off the road time

[itchyfeet]

Any test needs pass of fail limits or it's pointless, we don't have them?

From watching this video it seems that Plastiguage can be used to test against defined wear limits ...

https://www.youtube.com/watch?v=q3pHb-qXZc8" onclick="window.open(this.href);return false;

yes

and the defined limits for a WBX are what?

[Mr Bean]

By the way when I got my van about ten years ago the oil light used to flicker on at tick over when the engine was very hot. I didn't fancy a rebuild at the time so along with an oil change and filter I fitted a Kenlowe oil cooler, oil temp thermostat and a couple of PC fans. I got nearly two years out of it before they gave out. I kept it in when the recon engine was fitted and it does sometimes cut in under very extreme conditions. Yes I know its overkill but....
CS

[itchyfeet]

Nobody knows the limits for WBX then?

[Mr Bean]

My criteria is simple:
If an engine has clean oil of the correct specification at the correct pressure and it doesn't rattle or knok then it doesn't need fixing. i.e if it isn't broke don't fix it. Of course once you have it in bits...
CS

[Mohamster]

Nobody knows the limits for WBX then?

Hmmm ... I feel like this is a trick question

[itchyfeet]

Not at all, I genuinely want to know because it's not in the workshop manual

I have seen this quoted for other VW engines so may be a general VW spec, who knows?
http://uk-mkivs.net/topic/329297-18t-cr ... ?p=3193313" onclick="window.open(this.href);return false;

My point is plastguage is not a valid test if limits are not known.

Radial wear ... the target for a new part is stated as 0.02mm to 0.07mm and a wear limit of 0.15mm

[Jawin89]

Not sure if this helps but Bentley shows this for Aircooled



I think i have seen something in the Haynes manual about this but would need to check later.

[itchyfeet]

^^^side clearance, not the same, we are talking bearing to crank clearance and wear limits.

Crank diameters from factory are listed with tolerance range but not what the clearance to bearing is or wear limits

Not in Haynes either.

[Jawin89]

I have never seen any information on the wear tolerances for bearings. I would assume that the bearing shells are all produced to a standard size specification and the lateral movement measurement is all that is required to test the tolerances of these. Maybe measure new bearings and then measure some used bearing and see what the difference is. If the journal size is within spec and new bearing are bought then the tolerance would be the difference between the lower journal limit and the internal diameter of the new bearing.

Just a thought.