The vacuum pump has 3 check valves (poppet valves), one to the engine (exhaust) and 2 from the vacuum system (intake). If the exhaust poppet fails, your piston or diaphragm will be full of crud and there will be little vacuum which will take a long time to build up. Pulling vacuum on the pump from the in line check with a Mityvac will be impossible. If one of the intake poppets fail, nothing other will result than no vacuum. If two poppets, one on each side, fail, there is a chance of oil entering the lines due to blow-by pressuring up the crankcase. Unlikely to happen. On 11/1/05, Marshall Booth <[EMAIL PROTECTED]> wrote: > > Bob Rentfro wrote: > > So...if these check valves fail, how do I know? If I'm getting oil in > the vacuum lines is this indicitive of check valve failure? How can oil get > into the vacuum system unless there is a rip in the diaphram? Every other > time the diaphram has ripped I've gotten oil in the air cleaner housing and > none in the vacuum lines. I'm stumped. > > > > Oil in the vacuum lines USUALLY comes from a rip in the shutoff valve > diaphragm (on the injection pump) or from the transmission (if your car > has a vacuum modulator that leaks), but when the pump diaphragm is > damaged, oil CAN migrate from the pump thru the lines each time the > engine is shut down. For it to fill the lines takes some time (usually > many months) since when the engine is running there is some force > drawing the oil back toward the pump until the pump completely fails. > > As to diagnosing the pump - PUT a vacuum gauge on it, read the vacuum > produced and how fast the vacuum drops when the pump is shut down. > Covered in 43-660 of the chassis manual (attached). > > Marshall > -- > Marshall Booth Ph.D. > Ass't Prof. (ret.) > Univ of Pittsburgh School of Medicine > Department of Pharmacology 1300 BST > Pittsburgh PA 15261 USA > [EMAIL PROTECTED] > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: 43-660.pdf > Type: application/pdf > Size: 158525 bytes > Desc: not available > Url : > http://striplin.net/pipermail/mercedes_striplin.net/attachments/20051101/40d1247b/43-660.pdf > _______________________________________ > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://striplin.net/mailman/listinfo/mercedes_striplin.net >
-- Hans Neureiter, Houston, TX '82 300SD, '95 E300D
