On Tuesday I took the Turner engine (in my MGB "truck") to a machine shop
about 25 miles up Rt. 8 in Oakville, CT. I noticed that the MGB's oil
pressure at 3500 rpm's wasn't very good once the engine got hot. Only about
50 lbs. Off the highway it dropped to 25 at idle. A lot lower than usual. I
thought it might be from overheating oil, so took a minute, stripped the duct
tape off the oil cooler & pushed it fully down to expose all rows. (In winter
I retract it into the pocket I made in the bottom of the panel where in stock
MG's it normally sits on top. It hangs below to keep the radiator clear & the
2 openings in the front valance feed air directly to the cooler. I install a
duct from those openings to the cooler when racing.) That made a difference
coming back - on the highway. Once on local roads the pressure again dropped.
Wednesday AM, when I pulled off the highway it was at 15 lbs. WHAT THE HECK?
Now this is an engine with something like 10,000 miles on it. Oil pressure
should NOT be dropping like that. That night, I changed oil & filter (Only
3,000 miles since previous). I use Mobil 1, so 3,000 miles is no big deal.
After the oil change, when I started the engine to check for leaks - pressure
went to 100 LBS! WHAT? Then it fluctuated between that & 20 lbs. Absolutely
crazy!
Drove to work today & pressure was low normal. At traffic light off the
highway - 10 LBS!!!!!!!! OH S - - - ! Consulted with my two best MG Brains
during the day & we considered the following: A - something clogging the feed
line to the pressure gauge (if so, 100 lbs. would be unlikely); B - a bad
pressure gauge (a very rare occurrence) or C - a jammed relief valve (most
likely).
Just finished the repair. It was the valve. It had jammed so tightly that I
had to use a thread tap to twist it out. The valve (piston-type) was badly
scarred on one side. I guess I'll be changing the oil & filter again real
soon. Used increasing grades of wet/dry sandpaper to deburr & polish it. Now
re-installed all seems well.
Norm Sippel
'66 MGB
But, - awfully scary moments.
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