Hydro suspension.

[koan]

I wonder what, if anything, is different between the HPF and non-HPF pumps.

I've had the cover off my 6.9 pump and have the SLS pump in pieces in front of me. My initial thought was that the pistons are of smaller diameter in the SLS pump, but that could just be that my "diameter memory" is not too good.

I will say this, when I recommissioned trusty rusty after the suspension refurbishment, I had the W126 SLS pump in place.

The pumps were rationalised to a one size fits all at sometime and "HPF" no longer stamped on the cover (again from Walter Hanel), don't know about the two pairs of digits. So the 126 pump could be well be one of the later versions.

koan

[s class]

I simultaneously had the original 1976 HFP pump and two 80's W126 SLS pumps apart at one stage.  I saw no difference inside. 

[koan]

Since I'm 100% going to ditch this pump anyway, i have reinforced the front O-ring seal by coating the whole thing in loctite gasket maker - If it leaks, it will never leak from the front cover again.

That front o-ring seals the middle low pressure suction part of the pump.

But if the front internal high pressure o-ring (left one of the two 10s in posted diagram) is stuffed fluid is going to come out between the cover (3) and housing (1), it's at upwards of 200 bar pressure.

The front cover o-ring (12) doesn't come into it.

EDIT: And another thing, if the front high pressure o-ring lets fluid out it might well allow air to be drawn in as the car sits for an extended time which would explain why you then need to bleed the pump.

koan

[koan]

I simultaneously had the original 1976 HFP pump and two 80's W126 SLS pumps apart at one stage.  I saw no difference inside. 

I'll accept that, my visual memory got it wrong. But the text with the cross section says the pumps are similar which implies there's some difference.

If there are two similar pumps required the rational thing to do is just manufacture the "best" one and uses it for SLS as well as full hydro.

If that's the case SLS cars would get the HPF pump. No idea if this is what happened or when, if it is what happened.

Maybe your two 126 pumps are the rationalised HPF/SLS type .

Just had a look at the front of my pump which was new 10 years ago.

It has "50", "HPF-EK", "98" stamped on it in three lines, which makes what I previously posted about there being no HPF on recent pumps wrong.

EDIT: The gap between the front cover and housing on the SLS pump is about 5.5mm, much like the diagram but the gap on my 98 HPF-EK pump is much smaller, about 1.5mm (drill shanks).

koan

[koan]

One last thing then I'll shutup and go away - unless I think of something else

I have a (cheap) copy of a manual "Hydropneumatic Suspension System Models 116.036, 126.033 & 126.037".

Not much in it that's not in the 116 chassis manual but I came across this note in Job 32-640 "Removal and installation of pressure oil pump".

--

Note

Starting July 1977, the pressure oil pump on model 116.036 is supplied with a double lip radial sealing ring. In the event of repairs, install pressure oil pump of model 126, part number 117 230 00 64 with blue dot (arrow).

On model 126, from start of series of EK-engines (September 1981) an improved pressure oil pump will be installed. For identification , the pump cover carries the following letters - "HPF-E" or "HPR-EK"

(a poor quality negative fiche picture follows with arrow pointing to input boss where blue dot is to be found, the cover shows "35.81" and "HPF-EK")

Caption to picture:

Version of pressure oil pump HPF-EK
Production identification
(Example 35.81 = 35th week 1981)

---

I think that the "HPR-EK" at end of second note paragraph is a misprint and should be "HPF-EK" - like the picture.

koan

[Big_Richard]

Since I'm 100% going to ditch this pump anyway, i have reinforced the front O-ring seal by coating the whole thing in loctite gasket maker - If it leaks, it will never leak from the front cover again.

That front o-ring seals the middle low pressure suction part of the pump.

But if the front internal high pressure o-ring (left one of the two 10s in posted diagram) is stuffed fluid is going to come out between the cover (3) and housing (1), it's at upwards of 200 bar pressure.

The front cover o-ring (12) doesn't come into it.

EDIT: And another thing, if the front high pressure o-ring lets fluid out it might well allow air to be drawn in as the car sits for an extended time which would explain why you then need to bleed the pump.

koan

The oil leaking out isn't while its running, rather after its been sitting along time, it goes hand in hand with the air being sucked in. It must be the o-ring seal.

Its got one more chance, if i have to bleed it again, I'm going to be pissed off enough to pay for a new one

My refurbished rear subframe was reattatched recently, yesterday my drive shaft was installed. its a real prick replacing those centering sleeves but its all done now. Took the car for a thrash tonight, feels like its stuck to the road, point the steering wheel and it goes, no slop, no wandering. Look forward to doing the front now, thank god that's not a monstrously heavy single assembly like the rear. Absolutely astonishing, everytime without fail, driving one of these unsophisticated agricultural beasts puts a smile on my face. I cant say the same for the 126, i cant help but feel their an economised pile of shit 

[TJ 450]

If it doesn't require bleeding again after sitting, I reckon it will be fine.

BTW, the quote in your signature, PB, is my favourite of all time. You should consider a W126, plenty of room for your overnight bag and you can listen to Phil Collins on Compact Cassette through the awesome 4x6" speakers!

Tim

[Big_Richard]

No way - w126's in anything but perfect condition, swiftly belong at a scrap yard or in a crusher. The only things of value are, the engine, transmission and rear subframe components

They drive like an EA falcon, and it certainly appears they are as reliable and as well built.