Dealer misdiagnosis

[8bit]

A few weeks back we had a stuck brake on my wife's ML320 (2008, approved-used warranty in place). We had the Mercedes Assist guy come out as we were concerned it may not be safe to drive on. Chap arrived, had a good look, said the piston in the caliper was very hard to move.

Car was recovered to the local Merc dealer who said "no, it just needs a clean up and bit of grease" even after reiterating the road-side guy's diagnosis. They were adamant, did what they said, charged us about £150 and sent us on our way.

Weekend before last the same caliper starts sticking again. Took it in yesterday and now they're saying - you guessed it - the piston in the caliper is stuck. A bit of to-and-fro with the warranty company and they got approval to do that on warranty.

So, going back to the previous visit. As I see it, the dealer tech misdiagnosed the issue the first time round so in my view we should be entitled to a refund. They are, of course, just claiming that that was all it needed at the time and this is a new issue, but I fail to see how a caliper piston can go from working properly to corroded to the point where it's seized up in the space of four weeks.

Where do we stand on this?

[8bit]

kapiteinlangzaam said:

How did you pay for the first transaction?

Do you care if you piss the dealer off (i.e. is there an alternative one in the area for future work)?

First time was paid by credit card. Next nearest dealer is over an hour away - I think I see where you're going with this but we'd rather keep them on side.

aka_kerrly said:

Dealer can't win can it?!

What if warranty company said no to a new caliper as it is strictly a wear an tear item? Then you'd be thinking the dealer was great for trying to fix it for £150 rather than tell you simply splash XXX on a new caliper when the issue is only a new piston being required.

But that's not the case is it. To expand upon yesterday's visit, they initially said the piston was corroded and the warranty company refused the claim because they don't cover corrosion. I went back and asked them to have a close look at the piston seal and they discovered it had perished, thus causing water ingress. This then meant the warranty claim was valid as the corrosion was a symptom of the failure of a covered part.

So to summarise, they failed to diagnose the issue the first time round and didn't fully diagnose it the second. So your "poor dealer" rubbish doesn't apply here.

[8bit]

aka_kerrly said:

xxChrisxx said:

What...

If a piston is corroded enough to seize, the caliper needs rebuilding. As pistons don't just seize for no reason on a daily driver. It's almost always a fked seal. What the dealer did is called 'a bodge' not a fix.

Warranty companies are also pains for misapprehending words like 'corrosion' and 'wear' as a way to get out of paying. Even if its not a consumable or service item.

I accept your point regarding warranty companies. However since 8bit said the dealer explained that

8bit said:

"no, it just needs a clean up and bit of grease"

If a caliper rebuild is done thoroughly then yes new piston(s), new dust seal, new bleed nipple and some paint would be what I expect. However on a 7 year old part if there are no obvious signs of the seals being destroyed taking it all apart, cleaning/greasing and reassembling is hardly a bodge.

So put it this way. We have an initial brake problem, diagnosed by the Mercedes Assist technician as a stuck piston. We take it to the dealer who dismiss this outright, perform what they claim is a fix and send us on our way, £150 lighter. A matter of a few weeks later the same fault reoccurs. Dealer now concurs with the original diagnosis by the Mercedes Assist driver. Fault is covered under warranty. You really think it's unreasonable of us to feel unhappy with the dealer's conduct and diagnosis and expect that they refund us for the ineffective work they carried out first time round?

At no point during the original visit did the dealer say anything like "we think it might just need a clean up, if you want then we can try that first at a cost of £150 to you and see how it goes and if it fails again we'll look into it further." If they had I'd have declined and asked them to look into it properly in the first place. If they'd done that then they'd have correctly diagnosed the issue first time round and none of this would be happening now.

[8bit]

ging84 said:

if i had a caliper that was ceasing i would always have a go at cleaning and greasing it, would never go straight to replacing it.

If it was my own car then this - I don't have warranty on mine any more, it's a weekend car so I'm happy to do this stuff on it because I don't need it on a day to day basis. The Merc is my wife's car and this is what gets her to and from work, carts our 1 year-old son around, etc. etc., hence why we keep the warranty on this one as we get courtesy car cover if we need it too.

[8bit]

xxChrisxx said:

If it's been sticking on and getting hot, I'd watch out for them saying you need new discs and pads at the back.

Funny you should say that. First time it was in, when they said it just needed cleaned up, they said it needed a new disc on that corner, but not pads. They said the disc was scored on the outside and rusted on the inside. I declined, partly because I wasn't convinced of their diagnosis and partly because they didn't think it needed pads as well and I've always been told to change pads when changing discs. I fail to see how a disc could be corroded on one side if the caliper was stuck on, too.

Glad we didn't pay for that now. Funnily enough, this time round they didn't seem to think there was anything wrong with the disc.

Given that this shower are the only dealer any less than an hour's drive away (on a good day) I think we can safely say this'll be the last Mercedes we ever own.

[8bit]

ging84 said:

I don't understand why you needed to pay for them to repair a caliper, but the replacement was covered under warranty

We didn't, that's the whole point. Read my original post again.

[8bit]

UPDATE - Wife called the service manager at lunchtime and he didn't even try to argue, just agreed to refund the cost for the ineffective "repair" in full. We're happy with that, glad the dealer has done the right thing on this occasion.