M70 Topend Refurbish

 

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p. 1

intake manifold gasket valve cover gasket refurbish car 1991 bmw 750il mfg 4/91 symptoms very bad oil leaks from the valve covers along with pentosin leaks from somewhere rough idle when cold spark plugs needed changing and most of the fuel vapor lines were brittle and leaking from age and engine heat the following pages are picture intensive and serve as a detailed documentation of the processes i followed in trying to fix the issues as well as any pointers and lessons learned i picked up along the way hopefully they can also serve as a valuable reminder of how to put things back together again in my opinion if one was just interested in replacing the valve cover gaskets resealing the intake manifolds the job could easily be done on a saturday but if more is planned such as drilling the oil-spray bar banjo bolts safety wiring repainting valve covers replacing plugs replacing hoses rebuilding injectors etc one would be hard pressed to complete all these steps in a day i was in no hurry and the job took a month of casual work weekends plus i spent a bit more time than necessary on the cosmetic aspects of the work i also ended up rebuilding the hydraulic booster and replacing the master cylinder note if you are planning to replace fuel and vapor hoses it will make life easier to just cut them off during the disassembly stages and replace with new as you reassemble i ve included hose types measured lengths at the end of this procedure page 1 of 63

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this is a view of my engine bay before i began if this is your car take a good look it may be awhile before it looks complete again page 2 of 63

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not knowing how long this would take plus the fact i can never remember the before details i took a number of pictures around the engine bay to document general fuel line layout cable wire routing connectors etc page 3 of 63

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remove noise suppressor begin by removing the top cover/noise suppressor give the four screws two shown above on the top a 1/4 turn and remove the suppressor pull straight up this view shows the top cover/noise suppressor removed page 4 of 63

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initial disassembly this view shows a items requiring removal 1 dk motor/throttle body 2 fuel pressure regulators/fuel rails 3 fuel injector wire housing 4 maf mass air flow sensor 5 ignition coil disconnect only 6 air filter/covers note the vacuum lines from the pressure regulators these most likely need to be replaced due to heat and age page 5 of 63

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p. 6

left maf and airbox removal the right maf mass air flow electrical connector un-screwed and pulled off to the side next loosen all the hose clamps both sides of the maf unclip the air filter box cover and remove the air filter should come out with it if not remove it now next remove the 10mm nut on the rubber mount and work off the maf rocking it left to right to break the seal typically this rubber mount also needs replacement the old version is shown here right this view shows the left maf air filter cover removed note the breather hose has a check valve with elbow this is also found on the right side as well this connects into a hose from the pcv valve to remove the breather elbow pull straight up and it should slide out page 6 of 63

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left dk conn detail to remove the tab is pushed to the right yellow arrow this has the effect of le vering the connector out as you push both of these were very tight if too hard leave them until the throttle body dk assy is removed then you can grab the tabs on both sides simultaneously for better leverage left photo shows the right breather hose maf air box lid removed i labeled the vacuum hose for later id/replacement the photo above also shows qty 4 10mm bolts from the throttle body to the intake manifold already removed dk motor connector removal page 7 of 63

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above pvc system documentation shots note the check valve still connected to the breather hose and the pvc hose clamped to the intake manifold plenum this is the left side convention for this document going forward is when sitting in the driver s seat left is the driver s left and right is the passenger side page 9 of 63

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the pictures above show the pcv valves and assorted hoses each has a hose teeing off the main tube with a 90 degree bend this is where the check valve barb fits in the photo of the right side note the hose that passes under the dk connector and drapes over the valve cover this hose is from the tan/white connector solenoid valve you can also make out the chaffing guard right where it bends over the valve cover in the picture of the left side the hose just to the left of the dk connector is the hose from the black connector solenoid valve that broke when i was trying to remove it from the dk both pcv valves check valves and pcv valve cover grommets will be replaced page 10 of 63

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remove the pcv valves by pulling them up and out of the rubber seals/grommets both of these seals will most likely need to be replaced on your engine as they typically have hardened and leak top this is the right pcv rubber seal grommet in the valve cover bottom this is the left pcv valve rubber seal/grommet in the valve cover after the pcv valve has been removed page 11 of 63

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expansion tank removal the next few pages of pictures were taken out of the actual order in which they were performed i started out trying to minimize the amount of part removal but found i continually needed more maneuvering space so at this point you might as well remove the coolant expansion tank the windshield washer reservoir and the power cable b terminal to the alternator connection if you don t do the latter you ll get some nasty sparks 1 disconnect the coolant level sensor just behind the capthis just pulls apart 2 remove the cap and using a turkey baster remove as much coolant as possible 3 pull the overflow drain hose from right bulkhead 4 loosen the hose clamp from where the tank connects to rubber hose picture below shows it already loosened and the clamp slid down 5 remove the radiator overflow connection use side cutters or dremel tool with cut-off wheel page 12 of 63

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p. 13

hose removal tools i found the two tools at the right indispensable for removing coolant/fuel hoses they break the seal without damage to the hose or connector they re very cheap both came from www.harborfreight.com expansion tank removal remove the 2 plastic retaining nuts circled these two nuts hold the coolant expansion tank to the firewall use a 10mm socket to unscrew ensure you have a towel under the hose to catch the coolant that will spill when you pull off the tank the radiator overflow line item 5 in previous page pulled off its connector with a bit of prying using the lower pick tool in the picture above page 13 of 63

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washer tank removal page 14 of 63

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p. 15

disconnect powe page 15 of 63

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