Mercedes A-Class 2001 diesel engine injectors

The information on this page has been supplied along with the photographs by Rick Horden (rickbenz) with a view to enlightening owners of Mercedes-Benz Diesel powered vehicles of a problem on the fuel injector system on the 'A' Class A170CDI, this problem may also apply to other Mercedes diesel fuelled vehicles.
Please note that the photographs are added for interest but do not necessarily relate to the adjacent paragraph.

History

When Rick bought his Mercedes 'A' Class in February 2005 he was well impressed and being a 2001 A170CDI he knew that he was not only benefit from the economy of the diesel but also the torque. He had bought the car from a Subaru Garage, Lucas of Mansfield and as well as having been told it had been subject to a 121 point inspection and safety check also made sure that the car would be covered by a warrantee period, which was
three months even though the car had only covered 38000 miles. One could ask at this point, with belt and braces how could he go wrong?
Rick drove his prize possession home, and like

many of us did his own inspection producing a
list of defects as long as your arm, which
included steering column, front brake discs,
blown bulbs and even white indicator bulbs in
white reflector housings. The garage supplying
the vehicle took all this onboard and the work
was carried out at a Mercedes Garage.

Some six weeks later after having done several long runs Rick became aware of a problem which initially appeared to be either an oil or brake fluid leak which he spotted on his driveway, his inspection revealed that the under-body panel was also covered in an oily residue, as a result it went back to the retailer again. This problem led to the car going back a total of seven
times before the fault was located,

a leaking injector was the cause of the problem.

After the final visit and some 5 months later the problem appeared to have been corrected and Rick got on with life and the pleasures of driving his Mercedes, by this time the car had covered 45000 miles.

However this was relatively short lived when after covering only another 6000 miles during which time the car had run well, Rick suffered the experience of having an injector blow on his engine, an experience he would not want repeated, the engine sounded and ran like

a tractor rather than a Mercedes-Benz and the incident could well have caused a serious accident.

It now appears that the garage where it took 5 months, and 7 visits to locate a leak on an injector, instead of doing a professional job had merely applied more pressure to the injector retaining bolts (torque bolt and claw) and in doing so had stripped or severally weakened the threads by over tightening.

(Another good reason for always using a torque wrench, not just to ensure that bolts are tightened but also not over-tightened.)

On close inspection it was obvious that it was
this that had led to the injector being blown from

its seating. By this time the car was out of the retailer's warrantee period for the work that had been carried out and of course the garage would not admit to having bodged the job anyway he also realised now that it was a total waste of time taking it to this particular garage, if they had bodged the job once then there was every chance they would do it again. And as Rick himself says "he would rather let a Typhoo Tea chimp work on it than take it back to that garage" a little unfair to chimp's but I can appreciate his sentiment.

Rick now being confronted by a very large bill if Mercedes undertook the work, of not only the

engine problem but also rear springs, which also needed replacing, had to make some decisions as the car was now a non runner, after some thought he decided to investigate the possibilities of doing the job's himself.

Like the rest of us he found that his problem was exacerbated by the fact that there is very little information available on the car and that no Haynes manual exists, however e-mails that run into double figures to and from lofty resulted in him having sufficient information to assess the situation, and as a result he started the job.

His first major problem was getting the stripped thread replaced and a new bolt of the correct

length and thread provided, this could not be a standard Mercedes replacement bolt as the head of the engine had to be re-tapped (drilled and re-threaded) to replace the damaged thread, this resulted in using an 8mm diameter bolt, but the mechanic contracted to undertake this work cut a number 1 pitch thread (fine thread) so as to afford more torque, as is the case with the Mercedes thread, although this was a sound idea in theory it proved the cause of yet more problems as that thread value was not available, off the shelf on an 8mm bolt, which is normally 1.25 pitch, so Rick had to get the bolt made. Never the less undaunted he managed to find a company that was able to supply the bolt, in fact he ordered two. The injector that had been released/blown from its housed position due to the defective bolt was
re-usable but Rick had cut the retaining claw away to enable him to remove it, one more component that would have to be replaced, however the blown injector was salvaged.

Next problem, close inspection revealed the neighbouring injector held by the same claw and bolt had either leaked or was subject to heavy carbon deposits from the original or recent leak,

this needed to be checked out, Rick knew he was wasting his time if he just ignored it and so he decided to remove this second injector.

This however was easier said than done as it turned out the second injector was well and truly stuck which was why Rick had been compelled to cut the claw away, it appeared at this point that nothing was going to move it.
Rick spent a great deal of time struggling to remove this injector and tried all manner of things including soaking the area with solvents to try and break the seal of the baked carbon deposits, he did manage after a considerable period of time to move it slightly but that was it. Rick was in a catch 22 situation he really needed
to remove the camshaft cover to be able

to get at the injector but the injector had to be removed before the cover could be removed.
Rick was aware that in the process of working on this difficult injector he would cause some
minor damage to the cover and so had decided
to replace it anyway, he therefore broke the
cover away to provide him with the space he
needed.

Further attempts at its removal still failed and so Rick decided to confront the situation head on, a drastic situation calls for drastic measures, he decided to weld, yes weld a socket to the head

of the injector; this would enable him to attach a ¾ drive bar to the injector, that along with an extension bar did the job and the injector much to Rick's relief was out. One point to mention ,when turning the injector, rotate it clockwise or as happened with Rick the injector base will unscrew from the injector body and remain inside the injector housing. In Rick's case he lubricated the injector body ,replaced it back in the engine and was lucky enough to engage the threaded base withdrawing it complete on the next attempt.
This injector along with the camshaft cover, & claw would need to be replaced and so he ordered the these items from Mercedes, the injector was ordered from United Diesel
www.uniteddiesel.co.uk at a cost of £150.00

who offered a refund on undamaged injectors, next day delivery, albeit the refund aspect wasn't going to be applicable in Rick's case, as his stuck injector still had his socket welded to the top of it.
However the price was only half of the Mercedes parts price, even without the
refund and although the one purchased was reconditioned it had got a brand new Mercedes head on it.
Rick removed the two remaining injectors without incident, and these cleaned and coated with copper slip grease (MB Special grease) before being replaced and tightened down with the claw and torque bolt.

Regrettably, the replacement re-tapped hole and the newly sited stud did not hold and on road test failed quite quickly. Rick was now having to re-think the whole problem 24 hours further down the line and he had to re-tap the head again, this is the third time, the last twice he has done it himself, the first time he had it done professionally at a cost him £100.00 Rick is firmly of the belief that most owners will not be confronted by the stripped thread problem, that's unless they try tightening the claw and torque nut to cure the leak on injectors which will almost certainly not be effective in the long term

They may well be faced by the stuck injector and it is hoped that it is those owners this page will assist in overcoming the problem.

The fitting in the photo opposite is the one that failed.

Rick had to resolve this problem or he was going to need a new head which would of course mean removing the engine, this is something that is normally beyond even the most persistent owner as the engine obviously has to be dropped down rather than lifted out as with many vehicles . He had come up with yet one more idea, and he would tackle the job himself this time without the outside support of a professional whose charges were considerable even for the smallest of job.

He would get a stepped adaptor made up, In fact he had two made before achieving the fitting he wanted. It should be born in mind the the claw has to be positioned on the injectors and then slid over the stud and moved into position which is why Rick had the thread removed from the outer end of the stud this was to avoid damage to the thread and to make it easier to locate the claw. With the original bolt the injectors and claw could be manoeuvred into position and the the bolt fitted, which was an easier process.
The adaptor was made up with the smaller thread of 8mm, and a larger 14mm diameter thread, this screwed into the head, which Rick had again re-tapped. He was aware that the thread depth only needed to be 1.5 times the diameter
of the stud, as mechanically nothing is gained in the strength by increased thread depth beyond that rule.
The adaptors were made at a local engineering workshop and fitted by Rick. Using this method the hole in the centre of the claw which holds the injectors did not have to be enlarged and was not therefore weakened in the process.

He did of course have to allow a length of thread/stud long enough to cater for the claw and nut, this he did and everything fitted well.
Rick completed assembling all the components and with a little trepidation road tested the car, all went well and this fitting has held.

The problem of stuck injectors is apparently a common one on Mercedes-Benz diesel engines and can result in extreme cases of a replacement engine having to be fitted, the labour charge of trying to remove these stuck injectors being the prohibiting factor. One owner who has got two injectors gone at low mileage has managed to get MB to pay half of the £1200.00 quoted for replacing them, he is of

course still faced with a bill of some £600.00, no doubt plus VAT.
The owner of this car has also confirmed that Mercedes-Benz also encountered a stuck injector on his car "the likes of which they had not encountered before" "I wonder" they had this customers car for two days before returning the car in running condition.

The problem of the stripped thread is not to my knowledge a common problem BUT if you do not use the correct torque on bolts and nuts when carrying out repairs there is every chance that you will suffer the same problem , and remember like Rick it may not be you who caused the initial problem, your just left to pick up the pieces.

If there is anything that Mercedes-Benz diesel owners can learn from this experience its that if you see even a suggestion of a leak on an injector or under the car, not to be confused with water dripping of the air conditioning pipe-work, then get it sorted and soon. If you have unexplained oil deposits on the your drive or garage floor check it out, it could well be a diesel leak that has so far gone undetected. That way you will possibly avoid the experience that Rick encountered.

The other lesson than can be learned from Rick's experience is, if you have a leak on an injector do NOT just tighten the torque bolts and claw , you could well finish up with the same problem as Rick.

Remember there is no substitute for a replacement seal on the injector, which would not be a difficult job to replace on its own. Only when the leak is ignored for a period of time or the wrong action taken to correct it will problems of the type encountered by Rick be experienced.

No doubt some of you are left wondering what happened about the rear Springs on Rick's car, well he fitted them without problem while waiting for the spares from Mercedes-parts and United Diesel such was the complexity of the injector job that the rear springs replacement paled into insignificance.

I suspect that if Mercedes had quoted for this job along with the engine out to replace the head Rick would have been very lucky to get any change from £4500 which basically means a replacement engine, So what did it cost Rick to do the job?
The stud is 25mm long at 14mm and 75mm long with 40mm of thread at 8mm, total cost inc paying so called, specialist was approximately £400, £100 IDIOT SPECIALIST, £150 injector, £120 MB all other bits i.e. rocker cover, diesel injector leak off hose, rocker-cover seals, injector seals (copper washers), new claw, £40 2 x studs, £15 various penetrating/carbon cleaner spays, £10 re-welding aluminium cam follower which was accidentally damaged by splitting
A colossal saving on any garage price and not much over the price of one Mercedes replacement injector, this time the job has been done to Rick's satisfaction. It should be pointed out that Rick is an electrician by trade, and as a result has like many of us limited skills when it comes to modern vehicle engines, especially the 'A' Class which has with out doubt some unique features, Rick is of the opinion that many owners could undertake this job providing time and patience is available along with a range of well fitting tools, hopefully not too many owners will be faced with the stripped thread problem.

It occurs to me that IF I were to purchase a diesel, that the injectors want removing about every 15 20 thousand miles and the seals replaced, automatically, this would be a precautionary measure against the leaking injector in the first place and would not entail a great deal of work or expense if you can do it yourself, the seals would not cost a great deal of money and the satisfaction of knowing that you were not going to be faced with this problem would make it very worth while.
Good Luck Rick well done and long may she run, a very nice looking car and well worth what you spent on the engine.

Rick is a member of the www.baby-benz.co.uk club and I'm sure will attempt to answer any questions relating to this repair.
I have put this story together from e-mails that Rick send during and after the event, along with his photo's I hope you find it useful & interesting .

Rick has been on holiday and covered 1200 miles without incident engine wise at least, he has experienced problems with his all wheels but that's a story for another day.

Lofty