my 6.9 can't get it up !

[oscar]

Ian, have a look at the Haynes manual, for some reason it's got a 6.9 suspension diagram even though not applicable to any of the models it covers, but in that same section is the recommended flow rate for the pump at a certain rpm. There's about 4 pages worth of info including some diagnostics and figures. I'm at work ATM and can't quote the figure and I'd be only guessing to try and remember it.

When I first changed a pump on my 350 I forgot to replace a copper seal that goes onto the outlet banjo fitting. I started the engine and only noticed my mistake when fresh hydro juice cascaded down the front of my motor and onto the floor. I lost over 500ml of oil in the time it took me to realise something was wrong and run to turn the engine off. So the flow was fairly constant.

EDIT, sorry dude, I posted just after you and didn't realise so I'm bumping your last couple of posts

Hey you know what I just did this test and noticed the output of the pump is not particularly volumous, or linear, more like its spitting fluid.

I don't know what I'm looking for but I presume a fairly decent volume (car was idling at 1400rpm cold idle), and in a more linear / less spitting type of delivery.

Anyone got a video on what the output should look like? I'm going to shoot one now but it will take till late late this afternoon for the results to show up on you tube.

I.

Here we go, is this right or not?

http://www.youtube.com/watch?v=wC12X6wVPfY

I.

 

[TJ 450]

It looks like you found the problem, Ian.

It should be a continuous, high volume flow. That appears to be air, which could be sucked in anywhere on the suction side. How are your hoses, there are two on the suction side? The flare fitting on the suction side of the pump could also be leaking as it is known to cross-thread.

How long was the engine running for? It might take a while for all the air to bleed as well (a few minutes).
Also, how is the fluid level?

Tim

 

[B13]

It was fully warmed up by then, so probably around 650rpm in Park. At fast idle there was even less coming out, and mostly air.

I find it hard to believe there would be a leaking hose on the suction side, simply because there would be a small spotting of hydro fluid on the ground each time the car was driven, and the fluid level would be on its way down quite regularly. Its been static for 6 months or more now. When checked this morning it was about 1/2 way between the two markers on the dipstick.

Looks like I'll have to visit the wreckers for another used pump - the 280SE has one high up and easy to remove right?

As an aside, my wife watched the youtube clip and commented that the engine didn't even sound like a V8, I suppose thats a good thing, as where I'd placed the camera it would have been easy to hear all sorts of lifter / cam chain noise....

I.

 

[Des]

Not sure if you mentioned you had done it, but have you changed the little filters on the pump?
As from my own understanding it could ether be air or something in the system

 

[B13]

No. What filters? Didn't know there were any other than those inside and below the pressure regulator...

I was always of the understanding that those two were the achillies heel of the hydropneumatic system...

Ian.

 

[Des]

There's a paper filter, that gets replaced when the pump comes off, and a metal one you can stick an air compressor through it,

I don't know how much of a pain it is to remove the pump, but would it hurt to remove that, or all the lines and put an air compressor through that to blow out the air and or crap inside it?


Just some thoughts,

May need to give the Godfather a call when he is free for some more advice,

 

[WGB]

Sorry Ian,

Only just received your e-mail and checked the video.

My car has a steady bubble free flow when you disconnect that line and aim it into the tank.

I assume you left it flowing long enough to bleed the air out of the inlet line and pump but it still continued spitting.

Initial thoughts on seeing that video - you don't have enough pressure to even bother measuring it.

1) sucking air somehow - either low level in tank or leak in either of the rubber tubes or the cooler tube they are attached to.

2) Restricted inlet - rubber hose breaking up internally and acting as a flap valve, crap in the outlet at the bottom of the tank or a crushed cooling tube across the front of the car.

3) Pump or pump drive stuffed.

I would try the restricted inlet idea first as an air leak or a stuffed pump would be leaking fluid somewhere when parked.

Bill

 

[Bandolero]

That looks the same as Andreas" was till we replaced the pump.
We got one off a 280 with self levelling and it worked perfectly after that.
The pump will self prime so long as there is enough oil in the tank.
I can almost guarantee that pump is no good.

 

[Des]

I can almost guarantee that pump is no good.

Pump shouldn't be bad, my mechanic at the time, 2 years ago? Rebuilt it.

 

[Bandolero]

We tried to rebuild Andreas" pump as well but it made no difference so we fitted a second hand one from the wreckers.
It only cost about $20 from "U Pull-it". These pumps are reasonably cheap to buy from the wreckers and the common self-levelling ones are the same as the 6.9.

 

[Des]

We tried to rebuild Andreas" pump as well but it made no difference so we fitted a second hand one from the wreckers.
It only cost about $20 from "U Pull-it". These pumps are reasonably cheap to buy from the wreckers and the common self-levelling ones are the same as the 6.9.

That's interesting, I wonder do they have the same pumping power, or put out the same pumping pressure as the 6.9 pump?

We have talked in the past, I know not directly releated but the "bombs" or spheres from 560SEL's etc.. are the same type of "thing" but don't have the same pressure or ability to deal with the extra weight, I think Styria commented and confirmed this in the past. That's why they have different part numbers, and even different from the front bombs to the ones in the back.



So I guess my long winded and roundabout way of saying things then is, would the pump from a 280SE with self levelling actually be the same identical item?

 

[TJ 450]

AFAIK, the pump is of the same specification regardless of model, everything else differs.

Tim

 

[oscar]

Pump shouldn't be bad, my mechanic at the time, 2 years ago? Rebuilt it.

I remember that too Des, but there's no guarantee that the pistons are working well now if they might have been marginal before. I'm assuming that by "rebuilt" means "resealed". From the couple of reseals I've done and advice received over the forums, dust free environs during reseals were essential and if the pistons were removed that they be put back in the same holes in the same orientation due to the individual wear patterns. One particular spare I pulled apart as much as I could for the hell of it has one piston that just can't compress the oil. It looked ok dismantled and it's put together right but if I feed oil into it then cover the output with my finger and turn the shaft, three pistons will force oil out of the high pressure side but one piston simply fails.

As for 2nd hand ones, there's gotta be so many pumps out there that have run dry over the years and suffered major wear, particularly in unloved non 6.9's. By the same token there's probably lots of good ones. Priming them whilst unfitted and testing with a finger hard pressed against the output hole is a little quick evaluation method but remember that the output is supposed to be around 200bar (2852 psi according to Haynes). You might not know a pump is a dud until fitting it and/or accurately testing its output with a guage.

BTW, I've always assumed all pumps are interchangeable, including those on w126's and w123's.

 

[Des]

BTW, I've always assumed all pumps are interchangeable, including those on w126's and w123's.

Anyone got the Mercedes EPC?

That would confirm this, as if they are they would have the same part number

 

[B13]

Pump shouldn't be bad, my mechanic at the time, 2 years ago? Rebuilt it.

Eh, that pump went in the bin - sorry to see how much you spent on getting it rebuilt Des... after about 4 weeks of using the car on a daily basis it leaked so badly that hydro fluid was spraying on the exhaust manifolds, creating a white smokescreen - very undignified.

The guy who looks after my car (which is to say the Merc guy who fixes all the things I can't do on my own - which isn't that many) said its almost impossible to rebuild the pumps and have them work right / not leak, which is a pity because they are a simple pump and the rebuild kit is cheap.

His solution was to put a good used one in "much better success rate", which he got from a W126 of some description and that solved the leak problem. However I've never really been 100% happy with the suspension (as you well know the feeling when it was your car) and maybe its just that the pump in there was better than the rebuilt one, but still not as good as could possibly be.

Think its time to visit pick-a-part and walk out with all the SLS pumps I can lay my hands on - sounds like I'll need a selection of them on hand from here on in.

I.

 

[Bandolero]

Yes, they are definately the same as the self levelling pumps.
I agree, go to the wreckers and get as many as you can.
You will find a good one out of a bunch of them.

 

[Des]

So the pumps just slow down over time? and get to the point where they just don't pump enough to keep the car up?

Would be interesting to have them flow tested, on various cars to see what the pumps are actually pumping.

I know at the time my mechanic mentioned it was ether a few hundred dollars to rebuild or like $1600 for a new pump.

 

[oscar]

My take is that two things seem to happen to these pumps. Either the rear seal on the shaft wears causing suspension oil to leak into the engine's sump, or the pistons and respective cylinders wear down if not kept lubricated with suspension oil and/or contaminants wear them down. The pump is continually driven whilst the engine is running so it doesn't slow down as such it more or less loses its efficiency. No idea how long they should last but after a reseal, my 350's is the original pump.

I don't think it would be possible that a rebuild would include new pistons. By all means anyone correct me if a rebuild includes pistons and possible honing of the cylinders, I'd be interested, but I've never heard of anyone getting new pistons. A reseal kit from autohaus is about $15US and is simply a big o ring for the front cover, a paper gasket for the rear of the pump and a double lip seal for the rear of the shaft. 6.9's have an extra spacer plate behind the pump that needs another gasket but I've never seen one up close or know exactly what they're called.

Here's a few old shots of the internals. First one with eccentric shaft removed and pistons popping out.

Second one, a closer look at the eccentric shaft and the third, a closer look at the pistons removed.

 

[WGB]

I have been poking around the EPC and found the original part number for the 123 pump was 116 230 05 64 which is a different number to the 6.9 pump part number which was 116 230 00 64.

All have been superseded by the later part number 117 230 00 64 which was used right up to the end of the 126 500SEL.

I don't know what the difference is between a 123 and a 116 pump but the moral of the story is presumably to get a late model 126 one if you can as not only will it be newer but it will be the "recommended" one as well.

Bill

 

[s class]

I have a 420SE (circa 1986) pump in trusty rusty. I did disassemble and reseal it completely (despite the warnings of the low success rate of this), and its served me very well since.

Indeed, B13, that video of yours looks very sad. That pump is not even managing to pump without back pressure on it. I imagine that when connected to the pressure regulator, it must have been doing nothing.