MGB Register Forum

Were oil coolers originally a factory fit feature for 1973 B’s?
Cheers Geoff

My 72 BGT had one from the factory as far as I know.

Ian F

According to Clausager, the oil cooler became standard in November 1967. I don't know why. In my experience the MGB doesn't need an oil cooler, whereas the Midget does. On my last 4-pot MGB I had a thermostat in the oil cooler feed pipe which only allowed oil to pass to the cooler when the oil temp was above 85C. Even on a warm summer's day the stat hardly ever opened the circuit to the cooler. I could come home after a run, open the bonnet and touch the cooler to find it cold. It's not a good idea to run the oil cool - that's why the MGF has an oil temp gauge and the handbook tells you not rev the engine hard until the gauge reads around 80C or 85C.

My BV8 conversion had an oil cooler which I removed with no noticeable effect on the engine's temperature or oil pressure. I removed it because it was old and full of sludge and when I tried to disconnect it the union broke, so I simply left it off - easy to do on a V8 but not so simple on a 4-pot B series. The later RV8 also has no oil cooler. V8 engines get much hotter than the old B series, but the oil cooler still seems to be not necessary.

Hi Mike, this raises an interesting point I think. My BGT has an oil cooler which certainly gets very warm/hot after a long motorway drive, whilst my Midget , (Mk 1 with tuned 948 engine) does not, and doesn't seem to need one.
The interesting point is that both engines, A series and B series are very similar designs, so why do you think the Midget needs an oil cooler? Perhaps only the 1275 version?
Let me know your thoughts,

Ian F

Ian, on my last 1275 Midget the oil pressure would drop when the engine was fully hot. Adding an oil cooler cured that. On the MGBs I have had experience of, removing the oil cooler doesn't cause a change in the oil pressure. As I said before when I had the oil cooler thermostat in the hoses, it very rarely got hot enough to open the thermostat and pass the oil to the cooler.

I also hate the idea of all that old oil sitting in the cooler which can't be changed. When I took the cooler off my V8 I had a look inside it. It was not a pretty sight with sludgy deposits just ready to contaminate your nice fresh oil.

Thanks Mike, no substitute for first hand experience! I haven't noticed any similar drop in oil pressure in my 948 cc Midget. It does have a tuned engine (now 1000cc, balanced with a Piper cam) but seems to cope well with long runs.
Differences must be due to specific characteristics of each engine I suppose.

Ian F

The B series is a rattley old engine not made to the tighter tolerances of a modern engine. I'm sure the cooler keeps the viscosity of the oil up which helps. I take Bumpa;s point about his thermostat rarely opening on the cooler circuit. My cooler seems to get fairly hot but you can still bear to put your hand on it so I'm guessing something like 75 C. I find my max oil pressure doesn't vary much between 65 to 70 psi but at idle I do notice it drop from 50 to 30 psi when its stonking red hot. I can see when the pressure relief valve opens as you rev the engine. In general I would say that things are hotter under the bonnet of the B than the Midget. I never felt the need for an oil cooler on my 1275 Midget and I used to thrash it mercilessly.

For "stonking red hot" try a V8 in there. Twice the cc, twice the heat.