Faulty inlet manifold found after DPF replaced. Did the DPF need to be replaced?

[Charlotte60s]

I have an MB 250cdi Estate elegance (5yrs old, L reg). I took my car into the Salisbury MB dealership with the engine light on (not the DPF light) and loss of power - it had gone into limp mode. I'd called the AA and they said it could be the a faulty EGR and a blocked DPF, but that a garage would need to check the fault codes - P227985, P00B092, P246397, P226300 and P047164.

MB said that I needed a new DPF as they couldn't regenerate it. I asked them what had made it not regenerate. (Details of their email to me below). I paid £1136.00 for a new DPF to be fitted. Then I picked up my car and took it home. The next day I drove it, the engine light came on and I noticed the car was still in limp mode, so the problem hadn't been fixed. MB picked it up and took over a week to diagnosis (detailed in the email from MB) what was wrong. They said it was a cracked manifold and that it would cost another £825.20. They insisted that the DPF had needed replacing and that the manifold wouldn't have affected regenerating the DPF.

Email from Martyn Lewis at Salisbury MB Dealership:
Good morning.

In response to our phone conversation last night I have contacted our dealer principle and informed him of the situation he is currently away until Friday afternoon at which point he will be more than happy to contact you and speak with you.In the meantime please find below a detailed description of the faults and diagnosis on your vehicle from the initial visit to present day:

Week beginning 3rd August

Vehicle recovered into us from another garage with a diesel particulate filter fault and a loss of power. Initial short test dated 3-8-15 only shows fault:

P246397 – The soot content of the diesel particulate filter is not ok the system is restricted.

As part of the diagnosis we checked the history of regeneration of the diesel particulate filter that showed there to be unsuccessful regeneration cycles of the filter. The actual values of the filter show the fill level of the filter to be 400% the specified limit should be under 200%.The soot content is too high preventing the regeneration.

This fault showed an occurrence of 21 times.

No other faults with engine as per Quick test result

Following Mercedes Benz Technical document for this vehicle with this fault code the following steps were carried out:

- Acquisition of diagnostic performance data - ok

- Plausibility check of component B28/8 (DPF differential pressure sensor) - ok

- Compression test- ok

- Check installation height of fuel injectors - ok

- Check charge air system for leaks – ok - Via DAS pressure sensor feedback – see attachments

- Check exhaust system for leaks - ok

- Plausibility check of temperature sensors in exhaust system – ok actual values all ok

- Check electrical lines and connectors for emission sensor system – ok

- Perform wipe test on the exhaust system – ok

- Remove and inspect Diesel Particulate Filter – ok


Carry out forced regeneration of DPF fill level of particulate still too high at 250.7%

As stated in the attached documentation and test results a replacement Diesel Particulate Filter is required. We replaced the filter as per your authority and taught in the filter adaptation values and carried out the software update required in the teach in process. Clear fault memory at 10:33 on the 7/8/15 – Road tested vehicle and repeated quick test at 12:46 7/8/15 with no further faults in the system. During road test the car performed ok with no signs of loss of power no warning light came on.

Visit starting 13th August 2015 after vehicle collected 12th pm

Initial short test shows fault code:

P00b092 Boost pressure control – B has a malfunction – function or the instruction is faulty - STORED
P226300 The boost pressure deviates from the specified value – STORED

No other faults stored in engine control unit. Check wiring to charge system sensors – all ok
Following TIPS document GI5418p057924 check harness for chafing only found marks on outer loom insulation – strip and check internal wires all ok – re insulate harness. Clear fault memory and road test vehicle – loss of power experienced vehicle returned to work shop – Short test revealed several stored faults in the engine control unit –various faults in system checked all wiring to sensors all ok.

Check charge system pressure sensors with engine at standstill as per test instructions actual values ok. Test vacuum system that controls boost pressure all ok.
Test turbo charge air system with special adapter from Poole. Test result not ok found inlet manifold leaking. Traced air leak to inlet manifold below fuel filter. This leak results in a loss of power being experienced when the vehicle is driven each time. The only remedy to this is to replace the inlet manifold, if left the car will lose power in the same way it did on the way to the airport.

It is impossible to determine when this has occurred however there was no trace of this fault on the initial visit for the DPF fault as the vehicle was driven multiple times once the repair was carried out with no loss of power of faults displayed.

The cost to rectify this is £825.20 incorporating the discount for the age of your vehicle. The manifold itself is available for Friday along with the seals associated with the repair. I have ordered these in as precaution. if you would like me to continue with the repair please let me know I have not started stripping the vehicle as the message I received first thing left me with doubt as to your intentions.

Kind regards

Martyn

Martyn Lewis
Service Team leader
Mercedes-Benz of Salisbury
Sandown Group
SP1 2JS
Main number: 01722 411555
Direct Dial: 01722
www.sandown-group.co.uk

My next move was:
I received this email on 20th August, Thursday 1pm he'd sent it as I walked into the dealership to pick up my car. I took my car home as I didn't trust them. Martyn didn't even introduce himself to me as I politely asked for my car, I asked him for his name when he returned my key and that's when he said he'd emailed me. The dealer principal left me a message on 21st August, Friday 2.30pm to call him on Martyn's phone - he left no other number and I've not heard back from him. A BMW specialist (the garage my partner uses in Newbury) fixed my car replacing the inlet manifold (that I bought a replacement part on ebay for £60) that wasn't cracked but blown. This took another 10 days as he was busy.

I tweeted MB twice and neither times have they called me. I sent MB HQ an email requesting all the paperwork on my car for August to their customer service, who rang me and after 2 days and sent my request back to Salisbury MB Dealership. I received a voice message from Mark Lynch, Service Manager to say that I'd receive the paperwork as soon as possible. After 10 days, I rang Mark and asked him when he was going to email the paperwork and he replied 'what car are we talking about?' 'Who?' He knew who I was as I'd been put through to him by the PA and he was not wanting to help. I again asked him for the paperwork and he said it'll take 2 days. 15 minutes after the call he sent through the same email that Martyn Lewis sent me (above) on 20th August. This is now 22nd September! I replied to his email that this wasn't all the paperwork as there are a few pages saying 1 of 2 and only one is attached and that the dates and times don't add up. Within the hour I received another email with 2 pdfs saying this should be all I need. - Basically saying this is all I'm getting. I've not heard back from MB HQ customer services to see if I've got everything. I don't see any point wasting any more of my time asking MB HQ to check either.

I've kept the manifold part as I want to see if I can get my money back from MB as I believe, after speaking to other garages that they misdiagnosed my car with needing to replace the DPF. Especially as Martyn admitted to me that they were unable to diagnosis the faulty manifold for 10 days because they needed to wait for a special diagnostic machine from Poole to check the faults and they didn't have this when my car was first looked at to diagnosis the DPF needed replacing.

I wonder if the manifold hadn't been blown would the DPF regeneration have worked?

Are there any MB specialists that could give me their opinion please?
Supposedly, I have all the paperwork with the details from the MB Star system, if anyone is able to help me and look through the pdfs they've sent me and give me their opinion, please?

Thank you for reading this. I'm exasperated with my experience from both the MB Dealer and the MB head office customer service! I do hope someone can help.

Kind regards,
Charlotte

 

[Pookis Dad]

In my experience, it is quite difficult to diagnose something that the computer "insists" is something else.

Some of these guys are simply fitters as opposed to good old fashioned mechanics....

A few years ago, a friend of a friend had (the last of that model) a Vectra turbo diesel and it had been going into limp home.

They diagnosed a MAF (Mass Air Flow) problem and it had been replaced twice.

However, it didn't fix the fault, so I was called.

I looked into the Air Flow side of things and figured the intercooler had to be the problem. Reason being, it affected the "Air Flow" into the inlet.

I found a small hole that didn't affect normal running, but when full boost was demanded (throttle wide open), full boost wasn't being delivered.

New intercooler fixed the problem, but the dealer had printed out the MAF problem.

Sometimes you just have to dig a little deeper and have some prior knowledge of what "might" be the cause....

So back to the problem at hand. If the diagnosis flagged up a DPF fault, they went with that.

Likely because the DPF sensor wasn't receiving the full signal (not enough pressure because of the leak) so it decided the DPF was, in fact, blocked (which would present the same symptoms).

I understand exactly why you are mad, but in my humble opinion, they simply could not have second guessed the computer in this instance.

However, I would perhaps write to them and tell them what I have stated and suggest they could look for this as a cause in future and maybe even return some of your hard earned.

Very best of luck.

 

[star]

Sometimes a fault can cause the dpf not to regenerate and so blocks. they are prone to blocking even without faults. It is then difficult to determine what was the original fault was.

 

[Pookis Dad]

Sometimes a fault can cause the dpf not to regenerate and so blocks. they are prone to blocking even without faults. It's difficult to determine what was the original fault.

Which is my point.

If there is not enough pressure (the crack or gasket leak allows pressure to bleed off) the DPF pressure sensor will not detect sufficient build up of pressure (obviously) so no regeneration can actually occur.

Which leads us back to a leak BEFORE the DPF....

DPF is a good idea in theory, but excrement in actual working vehicles