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Diesel in the sump

Hi everyone. We are looking for some help or advice with a problem on our AV590 engined RM. After a reasonable run (over 50 miles) we are seeing some diesel (we think) in the sump oil. Easy to identify as the 'oil level' increases. We thought it was the injectors but have had these reconditioned and the problem remains. Any suggestions? Would really like to get sorted before something serious occurs! Thanks. Paul.

My bus number (if any): RM597

Re: Diesel in the sump

It depends on how much the oil level rises. More likely water in the sump caused by leaking cylinder liner seals.

My bus number (if any): RML2532

Re: Diesel in the sump

Two options if the injectors have been eliminated. There is a 50/50 chance of it being either one. So, fuel lift pump passing fuel into the injector pump and thence via the cambox overflow return into the sump; in theory this can't happen but it does; or the FIP itself is leaking fuel into the sump by the same route. Either will be a problem to resolve since although not expensive the success rate for lift pump overhaul is not great; many castings are either worn or porous. As for the FIP the most likely cause will be that the elements are passing fuel into the cambox because of excessive wear. The latter will be an expensive overhaul because the necessary parts are very difficult to find. That is assuming that the body itself is OK. Budget for maybe £2000 for a CAV NL6 or NNL6, a mortgage on the house if it is a Simms SPE6, and a sigh of relief if it is a CAV DPA, because it won't be the FIP in that case. There are reasons why you may well be quoted a significantly lower figure. DON'T just disconnect the overflow pipe and let it drain onto the road. The excess diesel in the FIP cambox is doing the camshaft and its bearings and all the governor mechanism a power of no good.

I would expect to see someone saying they can overcome the issue for 50 pence.

Of course as said, it hasn't necessarily been identified as diesel in the sump so the other option is coolant, but that should be easier to identify.

Re: Diesel in the sump

Well firstly thanks both for your knowledgable advice!

The moderate news is it's fitted with an NL6 I guess, and whilst we are 90% sure it's not water in the sump we will double check that first.
Would it then be a process of elimination? Lift pump recon, test, if no difference FIP recon? And do you have any experience of reliable and knowledgable companies to carry out the reconditioning of either or both?

Really appreciate your help.

Cheers. Paul.

My bus number (if any): RM597

Re: Diesel in the sump

I usually use a company in Essex, J&S Diesels. As roy says, it will not be cheap as pump overhauls are very about intensive. the last ones I had done came out at about £1k; they say they had to strip 3 pumps to make one good one.

It the increase in the oil level really that noticeable? Maybe someone fitted an electric lift pump on the bus? As we discussed elsewhere on here these usually lift fuel at about 4 bar and the AEC needs furl lifted at 0.4 bar. what happens then is excess fuel goes back through the spill-off/return pipe and can leak back through the injectors. I've found this on several RMs abroad.

My bus number (if any): RML2532

Re: Diesel in the sump

It depends on whereabouts in the country you are as to where it goes. I would certainly take it in rather than try to send it by carrier. There is more than one type of lift pump fitted to the AEC engine, not all can be removed without taking the injection pump off anyway. There is some merit in sending the lot away for testing and overhaul since the L/P is normally tested statically which may not show up it leaking, whereas if the FIP is motored then the L/P is operating the same way as in the vehicle.

In the South East, both 1st Diesel Services in Thornton Heath (Croydon) and Rochester City Diesel Services will still undertake work on this older type of equipment knowledgeably and reliably and have a good name. I have used both in the past. Colchester fuel Injection also have a good name. You will find that all the injection specialists who tackle older systems know each other and deal with each other sourcing parts. If you are elsewhere you could try phoning one of these and asking for a recommendation in your area.

Virtually all problems other than oil start in the fuel tank, so consider taking it off and cleaning it internally. Then think about additional filtration to protect a newly reconditioned FIP.

L/P lift pump. FIP fuel injection pump.

Re: Diesel in the sump

Thanks for all of the advice guys.

I'm tempted to get the whole lot off and reconditioned by one party in one go - even if that's for preventative maintenance reasons! In another 5 or 10 years who knows what may or may not be available? We used Peter Slater in Lincolnshire for the injectors and he did a good job. He also lists plenty of CAV fuel pump and lift pump details on his website I've now found, but it's good to have a few people to call - well for Stuart, the partner in crime and RM597s chief engineer, to call on Monday I should say!

If we do all of this should we look to change injector pipes too? The ones on there now are giving no trouble but didn't know if that was a wise move? Or is it a case of 'if it ain't broke don't fix it'? (If you hadn't guessed I'm not an engineer by trade!)

We need to do the water pump too as that's weeping. The bus came to us after 10 years of being parked up in the open on a farm. It really isn't good for all of the seals and gaskets we are rapidly discovering

Cheers

Paul.

My bus number (if any): RM597

Re: Diesel in the sump

Peter Slater is a well known and respected expert in his field. He will be the source of the parts many of the FIP specialists will have used in the first place, so you could do no better than entrusting him with the work. It is also very true that specialists do tend to hang on to particularly difficult to obtain parts for only their own customers' benefit. Yes I would take him the lot and explain the problem. AEC engines were notorious for breaking injector pipes so if you can get any for spares then do so. If the clamps are missing and you can get them then obtain some.

The AEC RM water pump is a PITA. If it isn't leaking water it is leaking oil. The first step would be to add barseal to the system since the repair is a minefield. It may well stop leaking coolant when the engine warms up. There are some very shoddy supposedly cheap rebuilds about. There are a lot of wear items in the pump; gear bushes, thrust washers and shafts, tapers etc apart from what leaks. Sadly some of these rebuilds have just just had a new old stock gland wacked in it for your money. The annoying thing is that you can spend a lot of time, money and effort, as below, on the things and they still leak. You may well be better off stripping it down to see what needs doing, obtaining a new gland from John Crane Seals Part no. 87079067 (which looks nothing like the original and which will require a modification to the impeller to fit as well as a new rubbing face. Martin Detheridge has the dimensions for the required rubbing face/ shaft bush to go in the housing.) Then entrust a proper alignment examination and the work to a local machine shop. If your pump is salvageable do NOT send it away for an exchange unit - what you get back could actually be in worse condition.

This sounds like the bus is going to have on-going issues for a while, get it onto concrete if you can. IF it has been stood unused for a long time outdoors I would expect you to find wheel bearing, braking and electrical issues. If that is the case then definitely get the fuel tank off.

Re: Diesel in the sump

You'll almost certainly have problems with the braking system, rear S cams and rollers seized up, accumulators worn and leaking to name a few bits!

To add what roy says, there's c company in wolverhampton who I've been told do very good water pump rebuilds.

My bus number (if any): RML2532

Re: Diesel in the sump

Thanks both. I think a call to Peter Slater is the next step. Really appreciate your help.

My bus number (if any): RM597

Re: Diesel in the sump

Hi Roy's

As per Paul's post many thanks for the useful comments.

Our injectors were overhauled by Peter Slater last July as were getting diesel in the oil & when I pulled them no: 6 was wet (the other five were good but needed over hauling. Obviously I then changed the oil & filter, since then we've not done a lot of miles but it's been purring & oil level has remain perfect.

It's MOT time so last week I took it to get our accumulators re-charged as we were only getting 4/5 engine off applications and on the return the engine note changed. I only found time to start looking into this on Friday and we definitely have diesel in the oil again!!

Whilst Paul was communicating with you I was chatting to a few people on facebook & we are all coming up with the same thoughts & I checked with Peter Slater this morning he agrees and threw a couple more items in the ring for me to check on Wednesday.

The water pump is sort of a relief as we were losing coolant but not fast enough to find, & it was only when I was looking for a dropped washer that I found the water pump is on the wet side of damp (but nothing dripping to ground). This will also get some more attention on Wednesday - I suspect it's only leaking when it's running & warm & I guess could still be just a hose.

I'll update you all..

My bus number (if any): RM597