I suppose 4 miles was not more than 10 minutes. That's hardly enough
time to get the oil hot. But regardless of how long it runs or how
hot it gets, oil pressure should never go as low as 15 pis (unless
you have 300 rpm idle speed).
You didn't say if it was an old engine or freshly rebuilt.
Engine in good condition should have 50-70 psi at road speed
(depending on pressure relief valve setting). It should also
maintain 40 psi oil pressure at idle speed (700-1000 rpm), or at
least 30 psi with abnormally low idle speed (~500-600 rpm). When I
see 40 psi at road speed and 20 psi at HOT idle, it's time for
serious investigation of the oil system. Good pressure in past going
gradually to low pressure now, suspect worn con-rod bearings. Bad
bearings is commonly accompanied by bearing knock. Low idle pressure
with no knock, may be low oil flow rate, suspect pressure relief
valve stuck open. Low pressure when you got the car, could be
anything, but check oil pressire relief vavle, oil pump, and conrod
bearings in that order (easiest things first).
Overheating is sometimes a relative thing, but it should not peg the
gauge on a 10 minute drive. Defective thermostat, stuck shut or
barely opening, might be the first suspect. Check to be sure the fan
belt is snug. Also be sure the fan blade is right way around, convex
side forward, concave side rearward. For car with heater, three
4-inch air hoses should be in place, as well as the felt pad under
bonnet on top of radiator. For no heater, one air hose left side
forward, plus blanking plate on right side of radiator mount
diaphgarm. For short trip light to light city driving or standing
still in stop and stop traffic, a fan shroud is amazingly effective
at keeping coolant temp under 220dF.
Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com
At 06:23 AM 8/13/2010 -0400, thgun@comporium.net wrote:
>I took a test drive last night about 4 miles after finaly getting my
>1957, 1500 mga running. Engine starts fine seemed to run good on the
>road and then I noticed the temp rising and the oil preasure
>dropping. Temp when all the way up. Oil preasure about 15lb. Limped
>home cooled the car off. I checked the water and it was full. I
>checked the oil and it was full. What checking should I start at this point?
>....
_______________________________________________
Mgs@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
|