Low oil pressure after full engine rebuild. - MINI Cooper Forum
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post #1 of 37 (permalink) Old Nov 4th, 2018, 04:42 PM Thread Starter
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Low oil pressure after full engine rebuild.

I’ve rebuilt 1.4 mini one engine but I get low oil pressure flicker once car is at temperature. So today I finally got round to checking oil pressure and unfortunately it’s low, it starts around 2.75 bar but once I’m up to temperature it’s around the 0.5 bar so that’s why I’m getting the pressure warning light.
So I’m thinking it can only be pump, crank bearings, oil filter or a blockage? or I have done something wrong during rebuild?
I’m a bit gutted after all this work but I’m hopeful I can find the problem.
So for reference it has new crank bearings, new oil pump, new oil filter , new piston rings, new cylinder head gasket, new oil seals, new timing chain. Car now runs very well and get no engine management lights, just oil pressure warning light when car gets up to top temperature.
Any advice or thoughts would be appreciated. Thanks Donny

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post #2 of 37 (permalink) Old Nov 4th, 2018, 06:08 PM
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Originally Posted by buddyboy1970 View Post
Iíve rebuilt 1.4 mini one engine but I get low oil pressure flicker once car is at temperature. So today I finally got round to checking oil pressure and unfortunately itís low, it starts around 2.75 bar but once Iím up to temperature itís around the 0.5 bar so thatís why Iím getting the pressure warning light.
So Iím thinking it can only be pump, crank bearings, oil filter or a blockage? or I have done something wrong during rebuild?
Iím a bit gutted after all this work but Iím hopeful I can find the problem.
So for reference it has new crank bearings, new oil pump, new oil filter , new piston rings, new cylinder head gasket, new oil seals, new timing chain. Car now runs very well and get no engine management lights, just oil pressure warning light when car gets up to top temperature.
Any advice or thoughts would be appreciated. Thanks Donny

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when fitted oil pump did you put any instant gasket sealer around where the oil pump big round hole for the oil feed from pump to block, just thinking outside the box maybe new oil pump casting is not perfect and bleeding oil pressure from there, also when oil pressure is low they tend to top end rattle and tap from camshafts and lifters like a diesel noise. could it be possible new oil pump not happy just because something is new dont mean its ok, if have another one handy might be worth swaping with the old one see if improves the pressure


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post #3 of 37 (permalink) Old Nov 4th, 2018, 06:13 PM Thread Starter
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Hi Mike and thanks for your thoughts. I’ve Tried two different pumps, same result. I never changed the oil pump drive change, could that be a possibility? If the transmission belt was wrong size could that somehow affect pressure?
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post #4 of 37 (permalink) Old Nov 4th, 2018, 06:21 PM
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Hi Mike and thanks for your thoughts. Iíve Tried two different pumps, same result. I never changed the oil pump drive change, could that be a possibility? If the transmission belt was wrong size could that somehow affect pressure?
could be the small sprocket on crankshaft for oil chain rounded off maybe slipping over the teeth, its always the crank sprockets that wear on them a 100k 1.4 engine and turbo engines as running higher revs to road speed, or could it be poss the main bearing journals have worn before the bearing refresh, they dont tend to wear crankshafts before the bearing unless the engine has over heated in the past its all about heat built up or low oil at any point or dirty oil will wear the journal more than the bearing, can you feel any up and down movement in the crankshaft with lever bar

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post #5 of 37 (permalink) Old Nov 4th, 2018, 06:54 PM Thread Starter
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I never checked the journals, just fitted bearings over them. I assume I should have checked diameter when I had shaft out?
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post #6 of 37 (permalink) Old Nov 5th, 2018, 07:25 AM
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I never checked the journals, just fitted bearings over them. I assume I should have checked diameter when I had shaft out?
would of checked crank with this link below
https://www.ebay.co.uk/itm/4PC-0-100...~G-:rk:17:pf:0
also if my memory serves me right you might not of marked all main bearing caps and big end caps this could be the issue. will explain when engine are made in factory or if it gets rebuilt they line bore the engine block and main end bearings ie all main bearing caps are in place they send a cutting tool through them all which in theory would make them machined to fit one way and one direction,, hence why all engine builders use centre dot to mark all this.
so if the mains are wrong way around this can allow a few hundred or a thou more clearances on all bearings this is enough to lower oil pressure but still allow it to run and will get worse with heat hot oil..

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post #7 of 37 (permalink) Old Nov 5th, 2018, 11:42 AM Thread Starter
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Ok Mike, I think my engine is still goosed so huge amount of hours for zero gain, well apart from experience and knowledge.
When you state bearing caps, is this not the shell like parts that fit round the journal? If yes then these were obviously new?
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post #8 of 37 (permalink) Old Nov 5th, 2018, 12:04 PM Thread Starter
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Just thinking back, main caps were new but I reused big end caps and your correct I never marked them, I just used according to best fit
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post #9 of 37 (permalink) Old Dec 18th, 2018, 11:44 AM Thread Starter
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After much agonising I have decided my engine rebuilt was nearly perfect. Low oil pressure is probably related to using original big end bearings and not marking what clamp fitted what piston. I’m hopeful Mike reads this and can answer, I’m planning to continue my quest over the winter so question to Mike is: best option to fix, should I replace the 4 pistons with new and then I know no mix up or can I just fit new big end shells to current pistons? Is there a way to check gaps before putting back together end? As always, any advice or tips much appreciated. Thanks Donny
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post #10 of 37 (permalink) Old Dec 18th, 2018, 12:54 PM
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After much agonising I have decided my engine rebuilt was nearly perfect. Low oil pressure is probably related to using original big end bearings and not marking what clamp fitted what piston. Iím hopeful Mike reads this and can answer, Iím planning to continue my quest over the winter so question to Mike is: best option to fix, should I replace the 4 pistons with new and then I know no mix up or can I just fit new big end shells to current pistons? Is there a way to check gaps before putting back together end? As always, any advice or tips much appreciated. Thanks Donny
hi again how are you doing. what i always do on any rebuild or a refresh rebuild is mark everything before dismantle as big conrods big ends are matched as are the main bearings to the crankshaft,, what i have found on these engines if done around 70.000 miles and have never been cooked or run on low or dirty oil etc its possible to fit new bearings but goes with out saying the crankshaft its self needs to be measured with micrometer before deciding on whether just bearings or need a crankshaft grind,
this all said i feel your problem as conrods and bearing have been mixed up the safest bet would be to speak to engine rebuilder and ask them to rematch and check the bottom end,, prob looking at a £300-£400 bill at worst for grand regrind and just rebuild the block back to only the crank shaft and conrods attached state. they will have specialist tools to measure all that must be right,, and also check all journals are correct sizes, it just takes one to be 000,20mm thou out and it will bleed the oil pressure away and heat will make this worse,
i dont think your pistons are the big issue as you did hone the bores and reringed them if my memory serves me correctly, and there was no smoke or excessive crankcase pressures,, so engine out flip it leave head on it regrind crankshaft and bearing to fit should bring oil pressure back up again, the oil pressure circuit is not reliant on the pistons its all down to oil pump crankshaft mainly and cam journals but o no cam noises then prob fine

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post #11 of 37 (permalink) Old Dec 18th, 2018, 01:54 PM Thread Starter
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I’m doing well Mike, I hope you and the family are also doing well.
Thank you once again for sharing your amazing knowledge and pointing me in the correct direction. I just can’t give up now after all this work. I will keep you posted on my progress and I wish you and the family a brilliant Christmas and a very happy new year ��
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post #12 of 37 (permalink) Old Dec 18th, 2018, 02:49 PM
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Iím doing well Mike, I hope you and the family are also doing well.
Thank you once again for sharing your amazing knowledge and pointing me in the correct direction. I just canít give up now after all this work. I will keep you posted on my progress and I wish you and the family a brilliant Christmas and a very happy new year ��
you like me once i get a idea in my head i have to see it through, i bought a 4x4 a few months ago and its turning in to the gift that just keeps giving, so far all rear suspension arms and bushes, and then random not starting faults where battery goes flat over night,, that was a royal pain to work out as dont have jeep diagnostics so could no read much so all done with a multi meter and scope found it in the end rear door lock of all places, latest is warning lights for abs 4 wheel drive and dsc lights all on,, now looks like the centre transfer box is worn out after 70k, so in the new year i will be removing it and buying a £300 rebuild kit and rebuild it with new clutch pack for the centre diff as such, just keep throwing money at it,, all i seem to do at moment with cars, thing is once you in it your in it
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post #13 of 37 (permalink) Old Dec 18th, 2018, 06:14 PM Thread Starter
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Sounds a nightmare Mike but you will fix it..!! I love that saying “once your in it your in” 100% spot on, can’t give up now. ..
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post #14 of 37 (permalink) Old Dec 19th, 2018, 07:37 AM
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Sounds a nightmare Mike but you will fix it..!! I love that saying “once your in it your in” 100% spot on, can’t give up now. ..
i've rebuilt refreshed a lot of engines over the years think the biggest pain in back backside and was rebuilt twice due to me been young and green and so over the moon i had chance of buying this engine damaged audi quattro rr turbo 1989 it was wide body and a paid £2000 for it, hmmm dont thing you would find one these days under 20k, so this thing kept pressuring the coolant so had head off sent off for crack testing came back clear was so over the moon just gasket i thought,, that was the point of my costly mistake, got back together started it and hmmm had this very slight noise like a small end rattle,,, mr stupid at the time decided to drive it up the road this slight rattle turned in to big end bearing and engine out crank shaft out head back off again another gasket and stretch bolts, and those 5 cylinder crankshafts are not cheap to buy or regrind,,, the bit i had not taken in to account is the past owner who while this car was losing water in to the oil was still driving it and damaging the bottom end and cam journals,,, that turned in to a big money pit,,
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post #15 of 37 (permalink) Old Jan 4th, 2019, 07:04 PM Thread Starter
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Mike, have you any idea where I can find a crankshaft drawing for my mini. Or even just the dimensions? As always , any help appreciated.
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