Nate,
I really like your tales of MB fixes and such. Right now my vacuum pump is working fine but someday, down the road, it could malfunction and I will pause, and slowly the memory neurons will reassemble and I will then be able to fix the problem.
Keep the wisdom flowing.
Cheers,
Bill aka "kipsinc"
--- In diesel_mercedes@yahoogroups.com, "Nate" <vwnate1@...> wrote:
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> Tom's W-126 has been having intermittent vacuum problems for a while now , the vacuum would bleed away whilst driving leaving him with poor brakes , iffy HVAC and no engine shut off .
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> The design of the OM617's vacuum pump is robust & sturdy , it incorporates simple and reliable poppet typ valves , four of them .
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> One of the two outlet valves is built into the top vacuum fitting on the pump and seems to be the basic weak point , it had failed so I'd changed it but when it failed it's spring & disc had disintegrated and I wondered about where the mangled up tiny bits had gone , as the pump began to work after replacing the dead exterior valve Tom wasn't overly worried but after a few weeks the vacuum began failing again more and more often so he'd gone to P-A-P and sourced a used pump off some junker , someone had already been inside it and mangled up the screws pretty good (I hate ugly fasteners as I view them as poor craft) so I took the cover off and removed the valves & cleaned them , they were all in good shape , just being partially clogged with oil sludge from the car's DPO never changing the oil ~ the later model vacuum pumps vent directly into the engine so poor maintenance causes long term pump issues .
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> As the sun was going down , we decided not to attempt to take his pump off , rather I removed the connection pipe and outlet fitting / valve assembly and started the engine then watched the open port like a hawk whilst Tom revved up the engine a few times and *BINGO* a tiny bit of something came flying out the port and the audible ' thumping ' noise the pump makes , deepened a little bit indicating the pump was working so I stuck my finger in the open port (!WARNING ! rapidly rotating V-Belts , pulleys & fan here means you could get a finger or hand mangled or ripped off before saying Oh , SHI-) and was rewarded with a nice bit of suction .
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> Success ! I'd found the missing bits of the old valve , they'd fallen into the primary outlet poppet valve and held it partway open .
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> I leaned over and shut the engine off then re - assembled the outlet valve & fitting , re connected then positioned the vacuum pipe & re started the engine and was almost instantly rewarded with 21" + of steady vacuum signal and the sounds of the various HVAC plenums snapping & slamming as they began to move and take up their working positions .
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> Tom test drove the car and it shifted normally and the HVAC didn't pause nor randomly change from cool to hot , when the ignition key is removed the engine now halts nearly *instantly* rather than the usual shuddering to a stop from low vacuum & leaks .
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> Just to make it a good job , I replaced the old & stiff rubber three way vacuum connectors under the hood , they're only $6 or so apiece , I also removed the lower dash panel and crawled up there with a Mechanic's Lamp & found the two short rubber hose bits connecting the brown plastic pipes to the ignition switch to be firm and good , no oil soaking so I left them alone & buttoned it back up again .
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> Tom says he'll order up a pump rebuild kit soon and I'll rebuild him a nice spare pump out of the spare he bought and my spare pump & install it for 100 % certainty of proper operation .
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> Believe it or don't ,this is the short version as the spare pump was in sorry shape and much cleaning was done to it , other fiddles too .
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> -Nate
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