Engine: 2.3 F/Inj B23E/B230F: Change main bearings in situ?

[S40T3]

Hello, I have recently noticed a faint 'roar' from the engine of my '89 GLT. Only at motorway speeds and when the oil is hot. The slightest throttle will provoke the noise and it goes away as soon as I lift off, so I suspect the main bearings. I want to change the shells in case they knock the journals oval.

Anyone here tried to change the mains with the engine in situ? Can I get the sump off without dropping the crossmember as Haynes suggest?

I'm hoping to remove/replace the upper shells by pushing them round whilst turning the crankshaft. If that doesn't work I *could* replace only the lower shells as the wear is only just starting to show and I think that the lower shells do all the hard work.

A half-job I know, but I just don't have the facilities or time to take the engine out right now. Oil pressure light stays off at idle and the car only covers about 3k miles per year, so even this 'bodge' should see me out!

Any hints (or warnings) would be most appreciated!

[Clifford Pope]

I've never heard of a roar being symptomatic of main bearing wear. It's usually described as a thumping noise when the engine is revved up from low speed or when pulling hard. Unlike big ends which rattle at higher speeds when unloaded.

But if you are convinced the mains are worn, it is possible but the problem is getting clearance to drop the sump (Except on early cars which had a shorter oil pump drive and a shallower sump). The proper way is to unbolt the cross member, remove any brake pipes etc, then lift the engine as high as possible. You need a lot of clearance to get the oil pump clear of the baffle plate.

But it can be more easily done with a bit of ingenuity. Somewhere a long time ago I wrote up how to do it, or commented on another thread.
You need firstly to undo the front engine mountings, then jack the engine as high possible. Suspend it from a stout bit of timber across the wings (well padded) and lower the jack.

Drop the sump as far as it will go - it won't come free, but you can reach in through a 3" gap to unbolt the oil pump and let it fall into the sump. Then remove the sump.
Refitting the oil pump is very tricky - if you drop a nut you have to start again.

Two dodges I discovered:
1) Remove the nearside support bracket entirely. Lower the sump as far as possible, then swing it through 90 degrees and ease it out.
or
2) Unbolt the oil pump, then afterwards, bolt it back on normally. Then enlarge the hole in the baffle plate enough so that the sump will go back into place. (I refined that method by cutting the baffle but bending it upwards. Then after getting the sump into rough alignment, wedge a block of wood over the bent up plate and push the sump upwards to bend the plate back into position. Remove the block of wood )


Once you have the sump off you can unbolt each main bearing cap in turn and replace the shells.

But are the bearings worn? Have you tried using a thicker oil?

[S40T3]

Thank you Clifford, just the information I need! *BUT* you now have me wondering if the bearings really are worn, or is it just my innate paranoia? I will do some revving from slow speed and listen, but my thoughts are that the bearings, if worn, are only slightly loose and nothing will be heard unless the oil is really hot. I'm using 10-40 semi-synthetic oil and the car has 190k on the clock. I change oil and filter every 3-4k and drive gently. What I don't know is how the car was treated/serviced during its 150k with previous owners - the oil was pretty black when I got it seven years ago.

[classicswede]

A roar is normally a stuck fan. Remove the fan and see how it sounds. To do the bearing for the couple of hours it takes to pull the engine I would not struggle with the bearings under the car.

[S40T3]

Bit of a bump/feedback.

It is possible to change main bearings in situ, although not something I would wish to repeat. A thin metal 'finger' can be used to move the upper shell to where it can be drawn round the journal and removed. Number 5 (with integral thrust washers) was very reluctant to go back in though.

Faint scoring on the mains, but hardly any wear. Big ends were just through the top layer (white metal?) after 190k. Lots of carbon in the sump, despite regular oil changes during the last 20k suggest that the car was not well serviced before my ownership.

I have probably wasted time, money and effort but it just had to be done. I would never have been confident in the engine if I had left it as-was.

A riddle: the main bearing shells have locating nibs opposite each other so that both nibs are preventing the shells from rotating in the direction of crank rotation. The big ends, however, have both nibs on the same side, so that only one nib is resisting rotation. I worried that I might have put the caps on backwards, but rod and cap numbers line up and witness marks on the old shells show that it was ever thus.

Anyone know what the brass nut (like a jet) above the oil pump outlet does? I blew into the outlet and some air came out of the 'jet' so it is leaking oil pressure. I tried to remove it to check but stopped before I snapped it off as it would not budge.