M20 oil pump

[zaq123]

m20b25.

I have the oil pan off the car at the moment. Pan had some sludge so I cleaned it and cleaned the oil pump (soaked it in kerosine and blew it out with a compressed air). Pump looks like new. Pressure valve didn't look too bad as well. I actually tested if it's holding by placing some thin hydraulic oil in the valve chamber and monitored if it comes out on the spring side. Basically just tested if mating surfaces are tight, who knows if the spring still in spec though.
Anyway, should I replace the pump while I'm there with new one? It looks like it's pretty simple design, not sure how and when these things fail.

Car has 170k miles on it and original camshaft was badly worn (cam lobes were down ~ 0.37- 0.4mm) and one tip of EX valve was mushroomed. Not e30 expert but it looked like oiling issues to me. If I recall correctly, spray bar had some sludge in it too. Never checked the oil pressure before I took her apart.
Oil pump gears looked good, no play or wear noticed. Should I still go ahead and replace it? How often do you guys see them fail? I don't mind to spend $300 if needed but it would be nice to put it towards countless other parts I need.

[dontrusthise30]

I've never seen one fail. I replaced mine when I built my new engine, but that's because I spent every bit of 5k building it (excluding turbo and EMS). So it was just good insurance. If anything with the oil pump goes bad, it's normally the stupid plastic pieces on either side of the oil rod.

[zaq123]

that's kind of what I'm thinking...
I would definitely replace it if I was rebuilding the block. As of right now, all I'm doing is the head/valves/camshaft/suspension/steering/drivetrain etc etc etc. Everything is still original in this car but I just don't understand how the cam can be worn so bad with only 170k miles unless someone ran her dry. Does camshaft known to wear on these engines so soon? Cam bearing surfaces don't look too bad though. If it's not usual for the cam to wear that much, I can only imagine what my crank bearings look like. I just checked the crank bearings for play and severe wear and everything feels solid (not knocks when pushing on pistons right after TDC). Would rather leave the block alone for now.

I've read somewhere that oil pump supplies are drying out for M20s? is it correct? If true, maybe I should go ahead and pick one up for whenever I will do the block.

[SkiFree]

I have rebuilt about a dozen M20 oil pumps at this point. The gears can get corroded and pitted (especially if water in introduced or if the oil isn't routinely changed). The plunger can wear asymmetrically (since the plunger rod is not concentric to the retaining washer), they will leak eventually (just takes a LONG time). The spring is pretty dang robust, haven't seen one out of spec yet.

If your gears look great, I would replace the plunger and call it kosher.

[SkiFree]

Everything is still original in this car but I just don't understand how the cam can be worn so bad with only 170k miles unless someone ran her dry. Does camshaft known to wear on these engines so soon? Cam bearing surfaces don't look too bad though. If it's not usual for the cam to wear that much, I can only imagine what my crank bearings look like. I just checked the crank bearings for play and severe wear and everything feels solid (not knocks when pushing on pistons right after TDC). Would rather leave the block alone for now.

In addition to the possibility of the engine running while low on oil (or not changed regularly) if an engine oil without ZDDP was religiously ran, then the cam (and rockers) can absolutely be wiped out by this point.

I would at least check the main bearings furthest from the oil pump.

[zaq123]

In addition to the possibility of the engine running while low on oil (or not changed regularly) if an engine oil without ZDDP was religiously ran, then the cam (and rockers) can absolutely be wiped out by this point.

I would at least check the main bearings furthest from the oil pump.

Thank you for your advice, will check it out. I put very thin hydraulic oil in the valve chamber and sure enough, plunger s leaking a little bit ( it set overnight). Do you think the plunger seat in the housing will not be worn as much as the actual plunger is?


On a side note, valve seals....any reason to spend $50 for OEM valve seals or $8 Erling will do?

[SkiFree]

On a side note, valve seals....any reason to spend $50 for OEM valve seals or $8 Erling will do?

No, no reason on this part. Just make sure you use the valve stem condom when sliding the seals on.

[zaq123]

No, no reason on this part. Just make sure you use the valve stem condom when sliding the seals on.

Do you guys use blue loctite on those 4 m10 pump bolts after the rebuild? Or those wave washers will keep them from getting loose?

[digger]

it probably wouldn't hurt, those wave washers dont do much in general, certainly you want them for 3 bolts attaching the pump to block

[zaq123]

it probably wouldn't hurt, those wave washers dont do much in general, certainly you want them for 3 bolts attaching the pump to block

thanks for the tip. BTW, I said M10..... pump assembled with m6 bolts, 10mm head....don't want disinform anyone..

[RicardoD]

Reviving this thread as this forum as usual is a goldmine of information. I took my oil pump apart and just wanted to document in case anyone runs into this thread again. My plunger looked fine but out of abundance of caution I will replace mine. My ultrasonic cleaner really does the job on parts like this.

[PEZ2]

Just wanted to add note on resurfacing the lid as part of the pump rebuild.

[bimmy]

I also just took my oil pan off recently and I’m wondering if I should be replacing my oil pump as well since the car has over 159,000 miles on it. I’m also unaware if the previous owner performed regular maintenance and would hate to take the pan off again if the pump does end up bad. In the meantime I’m going to clean it and see what may need replacing (hopefully not the whole pump) is there a recommended solvent to clean the pump with? Thx :)

[bangn]

Won't know until you check the teeth condition, the pumps last time I checked in November were on backorder worldwide for both m21 and m20 pumps. I ended up using a good used IX pump and used the gears from that as they run in reverse compared to the rwd pump. This meant the loading faces on the gears were really nice for my application.

Just use degreaser or diesel to clean

[CommodoreDave]

RicardoD How in the world did you get that spring + washer + c-clip back installed? I have been struggling with mine for the past hour and haven't the faintest idea how you would compress the spring enough to get that c-clip back in its home...