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MG MGB GT V8 Factory Originals Technical - Oil pressure problems
|Last weekend I replaced the front cover on my 3.5L, and this weekend when I finished the job up, I went to prime the oil pump (packed them with vaseline while rebuilding) I couldn't get the motor to build any pressure at all. I fought for a while, and then eventually pulled the oil pressure relief valve, and tried priming, and oil came shooting out of the remote oil filter pipes at a pretty good velosity. What gives? I used the same spring, and the same piston, in the same oil pump head (Buick head that says METRIC) as before. The piston slides into the oil pressure relieve valve cylinder pretty freely, so it's not "stuck" in there. When I took the system apart last weekend, there was some scoring on the oil pump mating surface, so I used some very fine emery cloth and cleaned it up a little bit, replaced the gears with new ones, and put everything together using ONLY the oil pump gasket, and no sealant inbetween the two units. I've heard of the relief valve sticking causing high oil pressure, but never the relief valve prohibiting oil pressure. I feel like I'm missing something pretty rudimental here, but I can't figure it out.|
I had a similar problem when installing the Rover 3.5 engine into my MGBGT.
I removed the distributor and made up a shaft with one end shaped as the bottom of the distributor shaft - in the UK there were two different versions, one with a male blade and one with a female slot. I then drove the oil pump directly using a cordless drill. After a little while the oil pressure came up satisfactorily - showed by leaking from the remote oil filter pipes, which hadn't been fully tightened and also on the gauge.
This process is described in Roger william's book 'How to Give your MGB V8 Power', which is well worth reading.
|I've been using my drill and turning the oil pump gear judiciously for at least a combined total of 10 minutes. I just tried it a few more times, and came to a few conclusions: |
I removed the oil pressure relief spring, and put the bolt back in its place. Then I detached the line feeding from the oil filter back to the motor, and sealed the end of it with tape, then had an assistant watch the open end on the oil filter, and while turning the oil pump clockwise, only air came out of the pipe. No oil made its way out.
Next we reinstalled the oil pressure relief spring, left everything else the same, and turned the oil pump again. This time not even air came out of return line to the motor.
This is what has me confused. Why am I getting air and no oil, and why only when there is no pressure relief valve installed. I'm trying to avoid yanking the oil pump head while the timing cover is in the car (limited working space) But I think that's going to be a tragic inevitability. :(
|Justin . . . you might check for an air leak where the oil passage is at the point where the front cover bolts to the block. If the gasket is incorrect for the cover, or has slipped slighlty, you will never pick the oil up from the pan. |
My two cents.
|I remember one B engine that wouldnt build up any oil pressure because the oil pump gasket was installed upside down. Might be worth checking, not to question your abilities, but I've built numerous engines for a british shop to a very high standard, and I was the one that put the gasket in upside down. You never know.|
|Justin - I suppose the pump drive is connected ? - that is to say the gearing is engaged and not removed with the distributor ?|
The electric drill solution usually does it, but you may have depleted the vaseline with all this trying.
Take the oil pipe off the remote filter head and stick a funnel in the end. Then fill the funnel with oil and turn the engine over backwards to draw the oil into the pump. If the dissy is still out, from memory, backwards rotation will be anticlockwise, but check first. Fill that funnel two or three times to make absolutely sure that the pump is primed, then reconnect the pipe and use the drill again, making sure that the direction of rotation is correct.
Leave the pressure relief valve in place, but make doubly sure that there's no swarf at the seal end.
If that fails, then I go with Gordon - an air leak between block and front cover, but that's very unusual.
|Just done a top-end overhaul and packing the pump cavities with Vaseline and using a drill on the pump spindle started oil flowing almost immediately. Clockwise is the normal direction of rotation. 'The book' also says to inject oil into the pick-up port before replacing the front cover.|
|Pump drive was engaged the whole time, and I eventually had to remove the front cover (for the second time in 2 weeks) and clean out all the passages, and blow out the pickup through to the oil pan. It looks like a combination of an oil filter plugging, and some gasket sealant in an oil passage in the front cover contributed to my problems. I'll take the blame on the gasket sealant part, I apparently got a little over zealous, but the oil filter thing really baffles me. Oh well, it's fixed now thank god. |
Thanks for the advice to check oil passages between the block and the head. I never would have thought to remove the cover and check.
Knoxville here I come!
|Ok I'm not out of the woods on this one. I could never get it to build more then a few pounds of pressure, and even that was sketchy. I'm running out of ideas here. |
The timing cover is new
The gears are new
The oil pump is new
All the gaskets are new
The oil filter is new
The oil filter lines are new,
The oil filter lines are installed properly,
The pump was installed properly,
The oil pressure relief valve moves freely in its cylinder, and it's new too.
I have no clue what else to do. It keeps pumping air, and very little oil.
Anyone have anymore ideas? My last idea is maybe something is blocking the oil pickup where it meets the block?
|Then logically there are only two options - air in the sump pickup or the relief valve is not working as it should.|
Check the oil pickup gasket has not been broken. Air here would break the suction.
On the relief valve - check the working surfaces are actually mating and the spring is not broken.
Otherwise you still have debris in an oilway.
|Had a similar problem after 3.5l motor rebuild,new double row timing gear was rubbing on a lug,blob? inside the timing cover so that the cover didnt seat properly,turning the pump with drill could hear air being sucked instead of oil.Regards Steven.|
|If it *is* blowing air then it must be sucking it from somewhere. From what I could make out the pressure relief valve dumps excess pressure back into the suction side of the pump, so that shouldn't be a source of air. If it isn't sucking air from the cover/crankcase interface then the only other source seems to be the pickup and where it bolts to the crankcase.|
|From pictures of GM/Rover conversions I've seen, the distributor in some appear to turn counterclockwise and some turn clockwise. Not sure which engines are which, but the point is, your drill has to turn in the same direction as the distributor. Just one of the simple things of which you have to be sure. Which makes me ask, "Can you mix and match components so that the engine won't work?"|
Another thing, if you take out the pressure relief spring, and don't use anything else to "jam" the relief plunger into it's seat, you won't see any pressure and/or flow as the oil will simply take the path of least resistance and go back to the pan.
It may not be the case for these engines, but most "V" engines, the distributor itself is a cap or plug in a oil gallery, so the excess oil bleeds back to the pan where the distributor would normally stop it. The best you can get is oil flow up the push rod tubes to the rocker arms and minimal movement of the pressure gauge.
Not to say there isn't another true problem, just be sure that your expectations are realistic.
Just to add my two cent's worth - I experienced a loss of oil pressure when starting my Olds conversion for the first time. Got 50psi on initial oil pump priming using the "drill spin up" method, but on actual engine start up had no pressure. After going through the obvious leak points, oil pump gear clearances, fouled pickup tube, bad oil gauge, plugged gauge tube, check of pressure relief valve function, vaseline prime exercise, etc, I chatted with Dan Legrou at D&D who advised me to look at the oil plugs at the end of all the oil galleries. Sure enough, a plug at the end of the bore (behind the front timing cover)that supplies the lifters had come loose (the machine shop had forgotten to stake the new plug).
Besides the two plugs behind the front cover, there are also two in the valley for the rifling that supplies oil from the pump to the valve train and I believe two more at the rear of the engine which are threaded rather than staked.
Not trying to alarm you, but another possibility worth checking. You can remove the fuel pump blanking plate and observe oil flow characteristics as you spin up the oil pump - if you see a large volume of oil cascading over the timing chain, a plug has come loose.
|G. E. Creswick|
|Come on now Graham don't scare me like that! Everything worked a few weeks ago before I got the bright idea to change my timing cover for a shiney new one. The new timing cover came off the same model vehicle as the old timing cover, as did the gasket, so I know an oil galley isn't blocked in that respect. I did go ahead and yank the oil pan, and the oil pickup and cleaned everything up. I'll re prime, and try again tonight and see what I come up with. The dizzy definitely spins clockwise, and the end of the oil pump gear definitely meshes with the dizzy without problems. I'm hoping and praying that the gods are shining down on me tonight. I really need a break here. |
When I first built the motor and primed it, oil shot out of the remote filter line like old faithful, and I knew everything worked. That's my expectation for this time around, and we're not reaching it.
Rebleed the gauge with somebody on the drill.
You say "as did the gasket".
You using a secondhand gasket?????
Shame on you if you are.
Could be the pick up pipe gasket in the sump, or a split in the pipe. Did you use flushing oil by any chance????
The pick up is absolutely crucial.
That's where my money is.
|When I said "as did the gasket" I was referring to the brand new gasket came from the same make and model vehicle as the brand new timing cover, and brand new oil pump. I ripped the timing cover off AGAIN tonight, and blew out all the lines, and checked, and everything was clean, all the holes lined up, oil lines going to their proper places, blah blah blah, and reinstalled everything, and primed, and again, no pressure. |
A few explitives, and some serious thinking later, I reinstalled the old cover, with the new pump, and gears, and gasket, and started turning with the drill, and BAM, oil pressure immediately.
|They MUST be different. Look again, particularly at the oil pump cavities and cover face. Did you check the clearance between gears and the cover face?|
The solution is apparent. You want a nice shiny front cover and the old cover provides oil pressure - therefore, get your old cover bead blasted, thus rendering it shiny. QED
Graham (see you in Townsend in about 4 wks)
|G. E. Creswick|
|Silly me, I never measured the gear clearance when installing the new timing cover. I figured "it's new, it's not used, it got QC'd from the factory, all is well." Well things obviously didn't work out that way. I'll look at the clearance when I get home tonight and see what is really happening. I bet that's where the problem is. |
I really don't have time to make this cover pretty right now. Maybe next winter I'll take it out and "beautify" it.
On a bright note, I've disassembled, and confirmed the rest of my oil system is in tip top shape. =) I just might make knoxville afterall!
This thread was discussed between 23/03/2003 and 02/04/2003
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