EAS pump piston seal replacement - help please

Sorry to be asking for help all of the time but here I am again, cap in hand, out of ideas.

I'm trying to renew the teflon piston seal in my EAS pump. I've got the pump stripped down to the point of removing the grub screw from the counter weight but I can not remove the CW / piston asy from the pump body. I guess the CW is just a press fit over the motor output shaft but I can't get them seperated. I'm reluctant to use WD40 as the pump needs to be clean to operate.

I've tried prising a screw driver behind the weight and hitting the end, nothing. Also tried pulling it off with adjustable grips on the piston con rod, again nothing.

Has anyone had a similar problem and if so how did you solve it?

As ever any help would be appreciated. BTW, it's a '96 P38 pump.

ive done a couple of these now and never really had a problem once the grub screw is slackened off .
rick.

It wouldn't come off with me either, but I managed to replace the seal with it in situ with the piston at TDC.

The grub screw you remove from the outside is just a bung. You realise you have to put a smaller allen key through that hole to access the grub screw that grips the shaft? This was not clear in the photo instructions I was using. I was scratching my head for a while.

I had trouble too releasing the counterweight assembly. In the end I gave it a squirt with WD40 and had a coffee. By the time I was full of dundee cake it was almost falling off.

I just cleaned out the WD40 once it was off.

lanmjdun said:

It wouldn't come off with me either, but I managed to replace the seal with it in situ with the piston at TDC.

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How did you manage that? I had hell's own job getting the ring off that holds the seal even with it all out in the open in a vice.

Thanks for responses guys, I managed it in the end. I just kept drving screw drivers down between the counter weight and motor body and eventually I could see it was moving. Wasn't easy though, for the benifit of anyone bringing this thread up in a search in the future, treat it like an interferance fit and keep going! The pump body end cap is cast and so is pretty hard.

Don't know really, the piston ring top came off okay, but the crank wouldn't come off the motor shaft - I was repairing it in the lounge and didn't want to get WD40 on the carpet along with the graphite that came out of the motor!

I bought the seal off the Dutch chap on eBay, even after translating the Dutch isntructions to basic English it took me a while to figure out the top of the piston comes off - I was very relieved when I did as couldn't figure out how to get the new seal in otherwise!

lanmjdun said:

I bought the seal off the Dutch chap on eBay, even after translating the Dutch isntructions to basic English it took me a while to figure out the top of the piston comes off - I was very relieved when I did as couldn't figure out how to get the new seal in otherwise!

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I got mine from him too. The Dutch instructions put me off, but when I looked back at ebay last week I noticed he had English ones now too, so I took the plunge