General 2001 2.8JTD, braking vibration/disc runout.

[BGD]

(Year 2001 Fiat Ducato 2.8JTD motorhome).

Around a couple of years ago, immediately after I bought the motorhome (which had only done about 40,000kms) , I had both skimmed front discs, which totally cured the quite severe “pumping” and vibration it exhibited when braking. I had the whole front brakes overhauled/lubed/cleaned at the same time.

Now, a couple of years, and maybe 25,000 kms later, I can feel that the pumping/vibration is gradually starting to return when braking, especially when braking from higher speeds, say above maybe 80kmph. It is only very gradually getting more noticeable, and is certainly still miles less pronounced than previously.

I'm guessing that disc runout is still the problem, and I'm thus getting high spots gradually developing in one/both discs once again.

When they skimmed the discs before, I recall that the passenger side (it's LHD) wasn't bad at all, but the drivers side one had become quite a long way out of true.

I do also remember them mentioning at the time that there was a lot of play in the wheel bearings, particularly on the drivers side I think.



I've had a good wade through various Ducato internet forums to see what I can find.
Apparently there is indeed supposed to be some play in the wheel bearings – they say the Ducato ones should run somewhat more 'loosely' than most others...and sometimes people/mechanics have thought this was a mistake and have overtightened the bearing nut and then the nearing has failed from being too tight.

I haven't got a full workshop manual for the 2001 2.8JTD, but the Fiat forum says the Front wheelbearing nut torque: (for a 2004 Ducato 2.8JTD, which I'm guessing is the same):

The Fiat recommendation for 33mm nut is 40 to 44 da Nm or 288 to 316 ft lb.
The Fiat recommendation for 28mm nut is 35.2 to 38.8da Nm or 253.44 ft lb to 279.36 ft lb.
I haven't got a decent torque wrench so can't check the torques here at home.




Skimming the discs certainly totally removed the symptoms of the problem, but seems not to have actually cured the problem itself.

So I'm wondering what could be the root cause? Loose wheel bearings? Wheels not perfectly balanced? Some problem with tracking; etc etc?


Have any of you come across such problems in the past with other Ducato front brakes?
What could you recommend, as well as skimming the discs again, to try to permanently cure the problem?

Any advice most gratefully received.

 

[moodrater]

The root cause with motorhomes it staying idle for several months of the year, capillary action holds water between the pad and disk and you get a spot of heavy corrosion there approximately the size of the pad. This rough part of the disc will grab when braking.

 

[BGD]

Thanks for the idea - but I suspect that isn't the root cause in ours case: we use the motorhome a LOT. Last year away for maybe 20 weeks in total, and so far this year we've already been away for 9 weeks. And on those tours we don't stay in one place for more than a few days.
In between touring, I generally drive the MH locally at least weekly.
Over 25,000 kms in a little under two years is tiny by white-van standards, but I suspect it's a lot more than most MH's.

Also, as we live on the Eastern side of Spain the weather is generally very warm and dry indeed. Very little rain, and very low humidity.


I'm thinking maybe it's a loose bearing, or tracking/castor angle or even suspension issue, as the brakes are fully serviced and perfect.

 

[moodrater]

Unlikely to be rust in your case most motorhomes are standing from november to march always the same things every year handbrake rusted on, leisure battery kackered,boiler valve damaged, front discs rusted, caliper pins seized.
Easy to check wheelbearings, jack the van hold wheel at top and bottom and see how much play there is. Spurious discs are about £30 I'd just change them.