I was asked about this failure with no crank journal damage I'd mentioned on another post. This my wife's '76 MG Midget-bought new when we needed another car and there was about zero 'out there' at that date that interested me. So she's the driver and loves this 'cute' little red roller skate-a new car with old technology. Move forward about 20 years (around 35k miles)and I notice one day that hot idle oil presure is down a few pounds from normal. I rarely drove this car and it could have been this way for some time as wifey wouldn't likely notice a few pounds on the Smiths gauge. No other indications/noises. The pan is easy to drop on these and with only three main bearings, I was always a bit leary of this engine anyway. There was some of the usual leaded fuel gray slurry in the pan, but nothing else of note. I started removing rod caps-inspecting/plasigauging/replacing caps one at a time and all was well and the same with mains until the last=rear main. The cap came off and the back of the bearing shell was blue=heat and about 'fused' to the crank jounal-more than oil 'stiction'. I got it loose and it 'popped' out. The bearing was now deformed with the half shell trying to make more of a circle. The upper shell was more 'normal' but both showed heavy wear, nearly down to the backing. Surprising to me that the journal was just fine. These engines use separate thrust bearings and they were also a bit out of spec. Anyway, I replaced all that and it's been ok since. I suspected that there may be some misalignment with the trans input shaft and crank pilot bearing, but frankly not sure. This has been run on Rotella 5-40 since it became available, but dino 10-30 Havoline in the early years. So that's the story-we watch the gauge pretty close now!
Rear main bearing failure-explanation
- Thread starter Lapham3
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Spun bearing, i take it on this engine that the rear main bearing is the furthest away from the oil pump? Its possible that journal is a bit off. Your really need to mic that journal and make sure its within spec and that its really round. Either thick oil at startup, some problem with a filter or the crank /bearing was never right from the get go. You really need to check the cap too and see what the diameter is and if its round with out the crank in. A tear down is really the only way to be sure its fixed.
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Guessing rear was furthest from the oil pump? '76 would be a little late for leaded fuel-bet that was babbitt in the pan, HDEO is a great idea, seems to work well in anything old.
At some point around that time the MGB got 5 mains. Labor and management were at odds in the UK auto industry back then and quality suffered.
I would guess spun bearing more than misalignment. If the trans was misaligned I would expect to see lots of wear on the front top bearing half, or whatever the opposite side of the rear was, and a fair bit of wear on the center.
If the pressure was low it would be worth your while to check the rod bearings. The 1500 is pretty weak as far as stock oiling goes. One gallery feeds the front main and #1 rod, another feeds the rear and #4 rod, and another feeds the center and #2 & 3 rods (one of these things is not like the others!). #3 is usually in the worst shape.
John Twist has a good video showing what can happen in a 1500 engine and some tips on how to fix it.
If the pressure was low it would be worth your while to check the rod bearings. The 1500 is pretty weak as far as stock oiling goes. One gallery feeds the front main and #1 rod, another feeds the rear and #4 rod, and another feeds the center and #2 & 3 rods (one of these things is not like the others!). #3 is usually in the worst shape.
John Twist has a good video showing what can happen in a 1500 engine and some tips on how to fix it.
No-bearings stayed in place-not spun-ears still on the alignment tabs-top bearing slid out with my old ground down hacksaw blade helper tool without drama. I don't really remember the oiling path in these engines. All a bit of a lucky surprise tho. Leaded fuel was/has been available and was the fuel used until this failure. This event/repair was done many years ago now-not that many thousands of miles ago tho. Just relating it.
many english cars were poorly made and tho simple were 20 years behind the us and Japan designs, I owned a Hillman and a Triumph.
water leaks, electrical problems, wire mesh (non oil wetted) air filters etc etc su carbs that had cork seals and always leaked
etc etc
water leaks, electrical problems, wire mesh (non oil wetted) air filters etc etc su carbs that had cork seals and always leaked
etc etc
If it did'nt spin, then its probably somehow oil related rather than clearance related( still could be a bit tight though). Is the oil filter on the front of the engine? A bad filter in its past could have caused this.
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Originally Posted By: bullwinkle
Guessing rear was furthest from the oil pump? '76 would be a little late for leaded fuel-bet that was babbitt in the pan, HDEO is a great idea, seems to work well in anything old.
I remember buying leaded gas into the 80's. I got my license in 85.
Guessing rear was furthest from the oil pump? '76 would be a little late for leaded fuel-bet that was babbitt in the pan, HDEO is a great idea, seems to work well in anything old.
I remember buying leaded gas into the 80's. I got my license in 85.
Originally Posted By: edwardh1
many english cars were poorly made and tho simple were 20 years behind the us and Japan designs, I owned a Hillman and a Triumph.
water leaks, electrical problems, wire mesh (non oil wetted) air filters etc etc su carbs that had cork seals and always leaked
etc etc
LUCAS, the Prince of Darkness electrics. It was "exciting" to watch gas drip from the SU pots on to the exhaust manifold on the non-crossflow Volvo B series. Sssssssssssssst Ssssssssst.
many english cars were poorly made and tho simple were 20 years behind the us and Japan designs, I owned a Hillman and a Triumph.
water leaks, electrical problems, wire mesh (non oil wetted) air filters etc etc su carbs that had cork seals and always leaked
etc etc
LUCAS, the Prince of Darkness electrics. It was "exciting" to watch gas drip from the SU pots on to the exhaust manifold on the non-crossflow Volvo B series. Sssssssssssssst Ssssssssst.
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That John Twist video is good. Opening up that center oil galley makes sense. We've done the same with the 'improved' Buick 400/430 engines that replaced the reliable nailhead.
I didn't like to recently see the OE oil pressure gauges going away.
The Midget gave some grief a few years ago as it would stumble and shutdown at odd times-then carry on again. Ultimately, I could verify spark loss and a Crane electronic replaced the Lucas-found out later that with most Midgets those had failed long ago.
I didn't like to recently see the OE oil pressure gauges going away.
The Midget gave some grief a few years ago as it would stumble and shutdown at odd times-then carry on again. Ultimately, I could verify spark loss and a Crane electronic replaced the Lucas-found out later that with most Midgets those had failed long ago.
I can safely say I've never seen a non-rebuilt OPUS distributor that still works (granted I'm pretty young). Closest I got was a 77 MGB last year - the guy said he had never (!) done any maintenance on it until it just died in traffic. He couldn't comprehend how amazed I was.
Going to an aftermarket electronic setup or 'downgrading' to a points-type 25D4 or 45D4 is the way to go.
Going to an aftermarket electronic setup or 'downgrading' to a points-type 25D4 or 45D4 is the way to go.
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