Reduced Oil Pressure, Was Ok!

[mhyphenl 10 1 Cars]

Engine rebuilt 350 miles ago. Oil pressure was on 3rd white line when cold and just above first white line on tick over when warm, moved up with revs quite nicely. It seems to have gradually reduced to second line when cold and below first line almost on red when ticking over warm, it only actually reaches just above the first white line when being driven! This could have happened suddenly but don't think so. The oil pump seemed to be in good order when rebuilt, dismantled and checked! When the revs drop a bit too far when the power is taken off and clutch dropped (as a lot of these cars seem to do!) It goes into the red and stop lights up. Am I right in thinking that this means that both the low pressure switch and the guage are both thinking the same thing and are unlikely to faulty and that the oil pressure really is too low.

 

Never dealt with low oil pressure so where do I start?

[Anthony 1,000]

Check the crank pulley bolt is tight - if this comes loose, you get similar issues as the oil pump drive is secured only by the clamping force of the crank bolt.

 

If the gauge and light are agreeing, it suggests that you do have a genuine pressure issue.

[mhyphenl 10 1 Cars]

what's the best way to do that in situ? Is it safe to stick it gear and tighten it? Is there anything else that could have come loose or popped out that I can get to without any major work?

[AndyCrom 64]

take the cover plate from the flywheel and jam the starting ring and then tighten the crank bolt, I would

[dcc 855]

I wouldn't do what Andy has suggested. I would put in in 4th or 5th gear, handbrake on, even get a mate to put a foot on the brake. and tighten it to the correct settings using a torque wrench.

[Tom Fenton 1,525]

Sorry but I prefer physically locking the ring gear to do it properly. Doing it in gear or whatever and you are basically winding up a great big spring in all the drivetrain.

[mhyphenl 10 1 Cars]

There's so much crap in the engine bay locking the flywheel isn't easy, abs, power steering and the relays and fuses for air con jam up any working space! can you get a toothed tool to do it properly? Where on the gearbox case do you lock it?

[Tom Fenton 1,525]

Either remove the starter, or probably easier, remove the flywheel plate between sump and gearbox.

[mhyphenl 10 1 Cars]

I've just been out to the car and I was able to easily tighten the crank pully with my normal wrench and the car in gear! I've not tried too hard without locking the flywheel for reasons mentioned. Started the car and I think it has made a difference but will drive it in a bit and confirm!

If the bolt was fairly easily moved will that have affected the oil pumps performance?

[Tom Fenton 1,525]

If it was properly tight then you shouldn't be able to move it unless you either lock the crank, or use an impact ("windy") gun.

 

Personally I would not use it now until you have properly torqued up the lower pulley bolt. If I were doing it I would remove and fully clean and degrease the bolt, degrease the threads in the crank tail, then use a medium strength loctite before torquing the bolt up with a torque wrench with the flywheel locked.

[dcc 855]

your not really winding a spring though are you. the gears are locked to the crank, which is the point which he wants to tighten. fair enough if it was the cam, but i would not be happy putting that force through an object not designed for it (not the flywheel, but the locking device - all it'll take is the end of the screw driver to shear off under too much force and suddently you have a bit of debris in your bell housing).

[dcc 855]

Also, there's not much easier method than getting a mate to plant their foot on the brake

[mhyphenl 10 1 Cars]

Tom, is it really likely to cause a problem on short journeys?! I need the car for work but only 4 slow miles away! Also what do you use to actually lock the flywheel??

[Anthony 1,000]

With the oil pressure as low as it was, yes, it's very likely to cause a problem and the shells have potentially already suffered.

 

With the bolt tightened as you have and oil pressure again looking sensible it would probably be fine for short journeys, but personally, I would want to do it properly as Tom described as if it comes loose again you risk damage. You've no doubt just spent a lot of money rebuilding the engine, so why risk it for the sake of a few minutes work to ensure it's tip top?

[mhyphenl 10 1 Cars]

I've just been for a quick run and its made no difference, while I appreciate the crank bolt needs doing properly and I won't run it until this is done what else can I look for?

Also again any clues as to best way to lock the flywheel?

[mhyphenl 10 1 Cars]

Ok started this morning, pressure very slow to build and lower than second line when cold. Clearly not sensible to drive so left it! Really could do with advice on locking the flywheel. Also any other causes of fairly rapid deterioration of fuel pressure?! I have a spare oil pump but want to try all non sump removal options first!

 

In terms of how the system works, am I right in thinking the the oil is picked up and pushed through all the capilliaries in the block and head then circulated through the filter or is it filtered first? I guess what I'm getting at is what order do things happen in the oil system andcan there be a blockage anywhere that would reduce pressure or increase pressure?

 

Lastly after only 350 miles most of which have had normal pressure, how likely is it that the loss in pressure is due to worn bearing shells? They were all replace and plastiguaged properly and torqued properly when fitted!?

[Tom Fenton 1,525]

Either remove the starter, or probably easier, remove the flywheel plate between sump and gearbox.

 

 

Really could do with advice on locking the flywheel.

 

[sport1901966 8]

Oil passes as follows i believe

 

Sump - pump - filter - up the block (oil pressure sender/switch at this point) - cant remember where it then diverges to crank/head/postin oil jets but im sure someone will be able to fill the gaps.

 

Having the car in gear with a mates foot on the brakes is a perfectly valid way of doing it. I'd be careful locking the flywheel in an improper way because you dont want to damage the teeth or the bell housing.

[mhyphenl 10 1 Cars]

Either remove the starter, or probably easier, remove the flywheel plate between sump and gearbox

 

 

 

Sorry Tom, What I meant was, what to you actually use to lock when I've removed the flywheel plate. Is there a toothed tool that bolts on somwhere or do you just jam somthing in? I've seen tools for sale for other cars that bolt on and have teeth that lock into the flywheel to hold the timing?!

[Tom Fenton 1,525]

Large flat bladed screwdriver. Done it hundreds of times. Never broken anything yet.

[mhyphenl 10 1 Cars]

OK, I'm going to try the correct tension on the bolt first, if there is no improvement where do we go next? Seeing as a tightning last night using the in gear method made no difference I don't hold much hope!

[Tom Fenton 1,525]

I would be getting a proper gauge on there next to see what pressure you actually have.

[dcc 855]

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[mhyphenl 10 1 Cars]

I would be getting a proper gauge on there next to see what pressure you actually have.

Tom,

 

Sorry to do this to you again but how would I go about that? Where would you measure it from and I'm guessing that it's a proper peice of expensive gear required to measure it?!

 

I know that the guage on the dash isn't a reliable measure but the fact that the light comes on when it hits the red would suggest that it really is low and not just a knackered pressure sender?!

[mhyphenl 10 1 Cars]

Ok, sorry so cheap guage from Burgen £30, Sealey £100. I'm guessing the screw into where the pressure sender is with one of the adapters. Probably better to take to a garage!? Unless the cheap ones are ok!? Machine mart do a Clarke one for £40

Edited April 11, 2013 by mhyphenl