Author Topic: Tips on resealing 6.9 hydraulic pump  (Read 1086 times)

Rolo

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Tips on resealing 6.9 hydraulic pump
« on: 30 March 2021, 11:40 AM »
I got a kit from George at Performance Analysis and we've done 2 housing seals and the pump is still leaking from around the housing.  It all started when we replaced the hose from the pump to the valve.  Pump starts out tight and leak free and then it starts leaking worse and worse.  The fasteners are working loose or a gasket is seating or what else could be happening?

The pumps are still available, but I'd like to avoid the $900 price.  Any tips for us before we get in there for attempt #3?  thanks

daantjie

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #1 on: 30 March 2021, 02:36 PM »
You might need to post a pic to show where it's leaking.  Did you strip out the pump completely and replace all 3 orings plus the shaft seal?
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #2 on: 30 March 2021, 03:55 PM »
I've done a couple of these.  If the inside has any wear it becomes unable to seal.  I did one 3-4 times and gave up and did another one that worked.

I ended up buying a bunch of the o-rings. In the kit I originally got from uncle kent had slightly different sizes than what I ended up using.

'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #3 on: 31 March 2021, 10:28 AM »
Wear causes the housing to leak?  I think we checked the shaft and we did use all of the seals in George's kit.  Seems like it's a fastner issue, but we'll look again for wear.  Thanks

Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #4 on: 12 April 2021, 12:01 PM »
So here's where I'm at.  Would appreciate input.

2nd attempt to seal was a fail.  We can find no reason for the housing and the cover not to seal up.

George at Performance Analysis has a used cover he's sending me and the pumps are still in production.

Try the cover (which seems really unlikely to distort) or new pump?

rumb

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #5 on: 12 April 2021, 02:14 PM »
Based on my limited experience it doesnt take much distortion of the body to make them leak.  If you havent got it after 2 attempts then I would suggest looking for another unit.

'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #6 on: 12 April 2021, 05:17 PM »
Now you got me really worried.  If I spring for an $800 pump, what's to say that reinstalling the hose -- which replacing is when the leaking started -- won't recur?  Man, this is infuriating stuff.

Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #7 on: 13 April 2021, 10:35 AM »
Darn parts fiche sites show the pump as available.  Classic Center says NLA for 15 years.  That's nuts.  Isn't this pump used on several models?  Now in search of good used.  Any leads for a pump?  Thanks

daantjie

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #8 on: 13 April 2021, 12:04 PM »
There's always a few on ebay in various states.  You can still find NOS ones but they are quite pricey if you can find them.  Martin Werminghausen also does rebuilds, you can always send your pump there however it sounds like yours might be toast and beyond salvage.
« Last Edit: 13 April 2021, 12:52 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

tcj

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #9 on: 13 April 2021, 01:32 PM »
Daniel is right, Martin can rebuild even this pump. Thats a good example why just exchanging rubber seals on HPF-Pumps, HPF-Struts and HPF-Valves is not enough in many cases.

Regards,
Thomas
112.021
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Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #10 on: 13 April 2021, 04:11 PM »
Martin did my struts and I'm in contact with him now.  Thanks everyone.  I did find a used rebuilt in Germany, but they require core exchange.  I'm going with Martin for now.

Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #11 on: 14 April 2021, 08:56 AM »
I got an email from the seller of the rebuilt used pump and they only charge $100 for no core exchange.  Anyone have dealings with SPOB in Deutschland?

I'm thinking of getting used rebuilt and having Martin rebuild my existing pump.  Keep one as a backup.

raueda1

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #12 on: 14 April 2021, 09:54 AM »
I can't help much here, but it brings to mind a related story worth sharing.

A few years ago at the M100 Lodefest event in Oregon one of the particiipants drove his 6.9 up from LA, roughly 750 miles.  His pump was leaking but he brought plenty of fluid and managed to get there OK.  But then something happened, the leak became untenable.  Mike Morris was in attendance and tried to help.  He's one of the true, old school MB gurus and does fabulous repair and restoration work in Walnut Creek (?) CA. 

They had practically no tools, parts or much of anything else.  In desperation Mike disassembled the pump and used a flat section of concrete to try to reface it.   :o  Everybody's mouth was hanging open.  It took a few tries but he eventually made it work with some kind of sealant and homemade gaskets.  It still leaked but the car raised up and the owner made it back to Cali.  You just can't make this stuff up.   It just goes to show that everything is possible.   ;D
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

ptashek

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #13 on: 14 April 2021, 10:20 AM »
I got an email from the seller of the rebuilt used pump and they only charge $100 for no core exchange.  Anyone have dealings with SPOB in Deutschland?

I've bought stuff from them before.
No complaints.
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Rolo

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Re: Tips on resealing 6.9 hydraulic pump
« Reply #14 on: 16 May 2021, 11:40 AM »
I paid SPOB for a used rebuilt pump a month ago.  With the order, asked if I could pay the core charge.  Then got an email link to pay the core charge and paid the core charge.  2 weeks later got an email asking if I want to pay the core charge or if I wanted to ship the core first.

So they've had my money for 2 weeks and no pump and no replies.

Now I'm in search of a good pump housing only, and I'll send to Martin to put together with my pump parts.  It wasn't the seals that were leaking, I had a cracked housing.