15 replies to this topic

[rendersonique]

Hi all,
OK, situation is that I had my engine re-built 6500miles ago, I have done 3 oil changes since that time, the most recent was 2 weeks ago. My oil pressure has always been pretty good. However, today, after a stint down the A52 at 70mph (I may be a mile or 2 out on that figure ), I noticed a sudden drop in oil pressure. I pulled off at the nearest opportunity after slowing down to a respectable 40mph and turned off the engine. I checked for oil leaks, and after letting the oil settle for a while I checked the dipstick and was quite happy that there was enough oil in the engine to maintail a reasonable pressure. Now my oil pressure is usually 80psi when running at high revs, and 45-50 psi at idle. This has dropped down to between a 30-45 psi which is concerning to say the least. I drove the car back from junction 25 M1 /A52 intersection via Risley, Borrowash to Chaddesden at a max speed of 40mph. Can anybody point me in the right direction as to where the fault may lie?? :?

PS. It does sound different now when applying more throttle, although I have difficulty in explaining this in words. No rattles or clanks, just different

[Realstoo]

If no leaks and drop in pressure and sounds different then my guess would be your head gasket? Especially after a hard (but legal ) drive . Only a guess though from what you said and it sounding different but no leaks. Cant think of where else the oil could go with no leaks exept into water cooling cycle.

[Wil_h]

It can't be the head gasket, this has no bearing on the pressure reading of the engine. The sensor position only reads the pressure in the crank bearings.

I'd check the pressure relief valve first, then the bypass valve in the oil filter housing. We'll assume that your gauge isn't broken, maybe worth a check. But after that it's engine out. could be a spun bearing or a blocked pickup at a guess.

[rendersonique]

If no leaks and drop in pressure and sounds different then my guess would be your head gasket? Especially after a hard (but legal ) drive . Only a guess though from what you said and it sounding different but no leaks. Cant think of where else the oil could go with no leaks exept into water cooling cycle.

Sorry, I should have mentioned that I have checked all of the plugs and there doesn't seem to be a problem (all look a nice tan colour) and there doesn't seem to be a problem with water in the oil (at the moment).

[S2000Steve]

Just had new spring in oil pressure releif valve.

It had the wrong one in, The pressure would start at 60 - 70 psi at idle then drop off to 35 - 40 psi under load. Was totally back to front.
Changed spring and adjusted accordingly and then pressures have been fine ever since.

[bmcecosse]

I agree - check the relief valve - but.........they really don't get stuck all that often.

[rendersonique]

I will check the the pressure relief valve, but the engine does sound like there is something wrong with it. Seems to be running quite lumpy

[rendersonique]

Hi Again,
I was advised to split the oil filter and check it for metalic fragments. I found a whole load of small particles. These look copper in colour. As I have never stripped an A - Series engine I am not familiar what these may have come off. Someone suggested Baulk Rings? Anyway, I now have removed the engine, and will proceed to strip it down to investigate, but if anybody has an oppinion on what the material may have come off it would be much appreciated.

[Cooperman]

Andy,
Strip it progressively and you'll find the problem.
So it's engine off box, remove head, remobe timing over and gears, then remove the pistons at which point you can inspect the big end shells. Then remove the crank and thrust bearings. By then you should have a good indication as to the problem.
If bits have gone through the oil pump, that'll need replacing.
When rebuilding, use new cam followers and make sure you take out the oil gallery core plugs and thoroughly clean the oil-way galleries. I use a wire coat-hanger and use it to pull-through pieces of cotton rag soaked in paraffin, then finally wash out with parts washer and use a high-pressure air line.
PM me if you need more strip/inspect/rebuild help.
Peter

[rendersonique]

Conclusion......Centre main bearing is shafted big style and it has damaged the crank to the point where it needs a re-grind . Morespeed suck .

So the next question is:-

This engine clearly needs a professional engine shop to do the work! Can anybody recomend a reputable engine shop in the Nottinghamshire / Derbyshire / Leicester area, not one full of YTS trainees!! Reason I say this is that I posted this same question best part of 3 years ago and the replies were 'Morespeed'. Cost me £1300 for the engine & its only been on the road just over a year after its resto. Its only done 6K!!

Andy

Edited by rendersonique, 17 September 2010 - 06:00 AM.

[rendersonique]

bump

[minidaves]

med or your local old machine shop

dave

Edited by minidaves, 17 September 2010 - 07:20 AM.

[Cooperman]

That is a strange failure for a low-mileage engine. One might wonder why as it could be a fault not directly related to the crank grinding. What are the adjacent big-end shells and crank thrusts like? They are fed from the same oil feed as the centre main and one might expect them to be damaged also. It could be 'muck' in the oil feed passage to the centre main causing low pressure locally there. Measure, very accurately, the diameter of the centre main to see if it has been ground slightly undersize. The wear pattern seems to indicate unusual wear at the thrust sector of the shell which is what would happen if slightly undersize by a thou or so, although that is not necessarily the reason.
I can recommend a good machine shop, but it is in Bedfordshire. They do all my machining and are exellent. It's a long way for you to travel though and there must be someone nearer who is OK and not over-expensive.

[Wil_h]

Interesting. My thought would be that this failure is unlikely to be a direct result of any machine shop. It seems to be a catastrophic failure of the bearing, suggesting a sudden lack of oil, or a bearing fault. I certinally wouldn't be blaming Morspeed.

As suggested above, look at all the other bearings, especially the bigends fed from the centre main. you need to look at how clear the oilways are too.

Have you measured the crank journal? I'ev had similar damage (scoring of the journal) but overall the journal was not worn. I cleaned it up, put new bearing in and it's been fine ever since. A bit of scoring isn't the end of the world.

[Cooperman]

Andy, do you have a central oil pick-up pipe? If not, you may have cornered fairly hard to the right and had a momentary oil starvation which will have affected the centre the most because it is feeding 3 journals plus thrusts.
Just a thought.