02M gearbox housing corrosion

[Willie]

Well had a pretty frustrating weekend, for some reason there seems to be a large amount of corrosion underneath the mounting bolt heads for the gearbox to clutch connection. I found this when I was servicing my 2003 LCR.

Need advice ASAP about mine or Seats liability for fixing/replacing this.
I have spoke to Seat customer services and the car is booked into local Seat dealership tomorrow 08.30.
Will the fact that the car is out of warrenty effect this?

 

[Willie]

Bump for people just getting home from work

 

[Willie]

Well car was into Seat this morning, they said they haven't see this before, took pictures and sent these to Seat technical to annalise these to see what will be done.
I'm hoping they'll replace the box as it seems like the drive shaft seals are leaking too.
Hopefully they can change the sump at the same time

 

[DPJ]

I'd be looking at an external source being the cause of that, Willie. I think you could rule out faults with the metals............

 

[Willie]

But theres no pattern to it like a leaking coolant line dripping onto to specific bolts, its all of them that its happening to and one of the clutch housing aswell.

 

[DPJ]

But theres no pattern to it like a leaking coolant line dripping onto to specific bolts, its all of them that its happening to and one of the clutch housing aswell.

I'm thinking something splashed up on them from the ground, or chemicals in the air near where it's parked, etc..........

 

[Willie]

I know what your saying but with the under tray I doubt this.
I hope Seat don't look at it this way.
As far as I'm concerned if there was a recommended service/cleaning or checks for the out side of this piece and i didn't do this then far enough, but theres nothing and as far as I'm concerned I've done no wrong, why should i pay for it
But what could it be if it was chemicals and how do I prove or disprove this??

 

[DPJ]

I've see that kind of corrosion on older ally blocks and components before...

I think it could be down to electrolytic action between different metals - but conditions damp etc can accelerate it. Do you live near the sea? (salty damp air).

 

[Willie]

Not really Dave, closest I've stayed was 3 miles for about 2 years and now 15 miles from the sea.
I was thinking it was more like a reaction between the two metals or perhaps a grease or sealant they use has accelerated the corrosion process
I'm really surprised there was nothing else came up when googling this problem

 

[UncleFester]

15 miles would be considered close unfortunately, close enough for the salt air to have a go at things - doesn't take long either, 3 miles away is certainly close enough. Once the damage was done it would eat away at the surface leaving it vulnerable to further damage.

That said it looks like surface only so if you're really bothered, just change the bolts and put fresh ones in - give them a nice coating of waxoyl to keep the elements at bay and if you pressure wash the engine area - STOP IT Dirt can be a good thing especially layers of it

 

[DPJ]

The corrosion resistance of aluminum is dependent upon a protective oxide film. This film is stable in aqueous media when the pH is between about 4.0 and 8.5. The oxide film is naturally self-renewing and accidental abrasion or other mechanical damage of the surface film is rapidly repaired. The conditions that promote corrosion of aluminum and its alloys, therefore, must be those that continuously abrade the film mechanically or promote conditions that locally degrade the protective oxide film and minimize the availability of oxygen to rebuild it. A modern and comprehensive document on the subject is the second edition of the classic CORROSION BASICS textbook. Some excerpts of that document are used here.

The acidity or alkalinity of the environment significantly affects the corrosion behavior of aluminum alloys. At lower and higher pH, aluminum is more likely to corrode but by no means always does so. For example, aluminum is quite resistant to concentrated nitric acid. When aluminum is exposed to alkaline conditions corrosion may occur, and when the oxide film is perforated locally, accelerated attack occurs because aluminum is attacked more rapidly than its oxide under alkaline conditions. The result is pitting. In acidic conditions, the oxide is more rapidly attacked than aluminum, and more general attack should result.

.............

 

[Willie]

My problem is that the bolts will no longer be at the torque setting as they were installed with as they don't have the same face contect they had originally.
If the sea salt was a problem why has this never been discussed either on here or the www?
I'm sure this cannot be the answer

 

[Willie]

Cheers Dave, have to get my Chemistry Higher books out for that one

 

[UncleFester]

What i would suspect is that most people don't own their cars long enough to notice it or simply never remove the lower tray to spot or inspect the damage. Every car I owned in Newcastle and then Hull suffered from this, Milton Keynes is the only place it hasn't happened

 

[DPJ]

My problem is that the bolts will no longer be at the torque setting as they were installed with as they don't have the same face contect they had originally.
If the sea salt was a problem why has this never been discussed either on here or the www?
I'm sure this cannot be the answer

I doubt there is any corrosion (or very negligible) where there is no air contact, so the mating surfaces (behind bolt heads) will be unaffected.

 

[Muttley]

My guess would be that the gearbox has been on and off the car several times, (you have aftermarket clutch and flywheel fitted, for a start) and perhaps this was done in a hamfisted way, which would crack off the aluminium oxide layer and expose it to further corrosion. It looks like the metal has fretted away a little under the bolt heads.

Does your single mass flywheel vibrate more than the standard one? Vibrations will make any tendency to fret worse, although I'd not expect to see these kind of results unless the bolts were not torqued down properly.

The torque settings shouldn't have been affected as long as there is still metal under most of the bolt head. Torque settings are calculated to give a certain amount of stretch to the bolt, ensuring that it stays done up. This stretch will only change if the bolt seat corrodes away completely underneath the bolt head, allowing the bolt to settle.

If you're really worried, remove one bolt at a time, inspect the aluminium underneath and if it looks bad, fit a steel washer and torque it up again.

I've just had a squint at mine (51 plate TDI Toledo), and there is no evidence of any damage.

Pressure-washing the engine would make any tendency to corrosion worse.

 

[Willie]

The stretch on the bolt heads is due to the forces excerted by the bolt head against the face of the housing, less face = less contact = less force. I'm 100% sure if I tried to torque these bolts to there make up torque the these would move due to less face to face contact.

I have had this car since mile 1, the clutch and fly wheel change doesn't involve these bolts as they are only holding the gearbox to the clutch housing, its the clutch housing to engine connection that gets split when the clutch is changed.
The engine has never been jet washed, this is seriously not advisable, lots of delicate sensor going about

 

[Willie]

What i would suspect is that most people don't own their cars long enough to notice it or simply never remove the lower tray to spot or inspect the damage. Every car I owned in Newcastle and then Hull suffered from this, Milton Keynes is the only place it hasn't happened

what did you do about about the corrosion, sell on?

 

[DPJ]

Does the car stand unused for long periods, Willie?

 

[Willie]

No, car used every day
Has done 85,000 miles in 5 years, FSH too