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MG MGB Technical - Oil cooler blown, replace gives odd oil pres(LONG)

My oil cooler sprung a leak a couple of days back whilst I was about 20 miles from home. I noticed it when I cornered and the oil pressure dropped sharply. I immediately stopped and discovered I had been losing oil for a few miles. I check the gauge all the time so I am confident that the engine wasn't run at any time with no oil pressure. I have since changed the old 13 row to a new 10 row cooler and new stainless steel hoses. I primed it all, complete oil change (mobile 1 15/50 as before) and new Champion filter(as before). Disconnected coil and cranked untill oil pressure came up (about 20 seconds). Reconnected coil and started it up. Now this is the odd part. Before all this oil pressure was always ~40-42psi at idle (hot)and ~55psi at 3000rpm (hot). Now it only gives ~25-30 at idle but gives a nice 60psi at 3000rpm. The other thing I notice is that just like before when I started the engine it would take about 1 second to get the oil pressure up, now it takes the same time but there is a nasty kind of metal on metal grinding for about a second. Im very conserned about this as I have a bad feeling that it is the bearings going without oil for a second or too.
Does this all make sense or do I have something to worry about?

Cheers
And sorry its so long.

Matt
Matthew Crabb

Matt. My experience is that engine damage can occur under the circumstances you describe. Similar thing happened to my daughter's car. Crankshaft journals showed significant damage, bearings were junk and the con rods were colored blue on the lower end. Pieces of bearing metal in the sump. I would, at the very least, pull the pan and inspect the rod bearings and center main bearings. Something of a pain in the neck, but much better than a rod through the side of the block. Les
Les Bengtson

Matt,

I once had an oil-cooler line rupture while I was doing a nice steady 70mph, my only clue was that the pressure started to drop and so I shut it off and pulled to the side ASAP. My result was no long-term damage and so this is not always fatal, just depends on how lucky you are when it happens...

The pressure you report sounds very healthy and the change you notice seems rather modest and could probably be explained by other variables and so this alone does not seem dire. However, new "nasty metallic noises" are a concern. I would follow Les's advise and inspect you oil and sump for signs of failed bearings or other unusall wear. When you changed the oil just after this event did you notice any metal particles in the drain pan or filter? The only thing is that if their was severe damage which could cause the noise you describe (spun-bearing??), I would expect to see a drop in oil pressure ounce things warmed-up, not a healthy 60psi.

You might take a second and try and determine if the noise is coming from starter motor, alternator, fan belt, etc. Possibly something else got tweaked and this is not actually engine realated at all.

Good luck.

Cliff
Cliff Maddox

The fact you saw the presure drop shows the engine *was* running without oil, and may have been doing so for a while when you didn't notice it, with all that implies for the engine. Which is why I'd far rather have big lights and buzzers than an insignificant gauge for things like oil and temp.
Paul Hunt

I have heard of engines running without oil for hours. I actualy know a man who built a trailer which had an engine in it that he would crank up and run without oil. The oil pan was plexiglass so that people could watch the crank turning! His trick was to install a huge radiator on the engine so it would run cooler, plus it only runs slightly above idle.
NOW-I AM NOT SAYING THAT YOU SHOULDN'T INSPECT YOUR CAR! IF YOU SUSPECT ANYTHING SUSPICIOUS-CHECK IT OUT. I just wanted to point out that an engine car operate without oil.
If you are hearing strange metal to metal noises they should be inspected. It may be a pain in the butt, but if you are nervouse about damage to the engine, go ahead and pull the oil pan and inspect your bearings. If the engine throws a rod you will have a whole heck of alot more work to do.

http://www.bardahl.com/news/news.htm
http://skepdic.com/slick50.html

Robert

Hi Everyone,
Thanks for the great advice, I have pulled the oil pan and had a good look, I could see no evidence of damage, great news!
The even better news is that after replacing the oil filter again the noise on start up has gone away, I think it may have been a back non return valve in the oil filter.
But as usual on thing is replaced by another, I now have a badly blowing exhaust, but at least thats nice and easy to fix.

Cheers

Matt
Matthew Crabb

Matt. Glad everything turned out properly. And, now you will never have to worry about whether your engine is just about to self-destruct as you are driving along the motorway. Les
Les Bengtson

theres always that risk, but I try to forget about it.

Matt
Matthew Crabb

This thread was discussed between 25/04/2003 and 28/04/2003

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