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JCHannum
09-11-2002, 06:33 PM
Do any of you gentlemen have any experience with the Ford 4.9L six? I have just aquired one that suddenly looses oil pressure after driving for a short while. I know it is not a bad sensor as the lifters collapse. I believe the relief valve is sticking open, bypassing. It has been sitting for a year or so, and may be gummed up.
Need to know where relief valve is located. Otherwise a good deal, can't complain on price as there was none.
Thought someone was involved with building up a six a while back.

mike thomas
09-11-2002, 06:42 PM
JC, No experience with this particular engine, however the relief valve is probably in the oil pump. Old trick, add one quart ATF to the oil. This should degum the valve. I have run ATF in the oil of old cars many times over about a 30 year time period to clean sticking lifters. I would not put it in anything I thought highly of though. Mike

Thrud
09-11-2002, 07:53 PM
Dont put ATF in the engine! Flush the engine oil using a motor oil engine flush (amsoil, GM) Park it where you are going to drain it. Put flush in and rund at elevated idle for 20 minutes. Stop. Drain oil, remove filter and let drain for 10 minutes then install fresh filter and oil. DO NOT UNDER ANY CIRCUMSTANCE MOVE THE VEHICLE WITH THE FLUSH IN IT! - You will pooch the motor doing that!

trap
09-11-2002, 10:59 PM
ATF works great in an engine. It does clean lifters like magic.

Need more info on when it looses oil pressure. Does it always have good op when starting cold? everytime? how much does it drop when it drops? do you have a gauge? Sometimes an oil pump or pickup screen will act the same way when the bolts are loose.

JCHannum
09-12-2002, 07:40 AM
Thanks for suggestions. I had thought about ATF myself. Dumped in some Rislone to see if that helps.
Loose oil pump or screen may be posibility. It always has good pressure when starting every time, and can idle for long periods with no problem. After driving about 10 miles, it drops to 0. I am using the dash gauge, but it is truly droppong, as the lifters start to collapse if I don't shut off.
If I shut off and restart, it comes back for a bit. If I let it cool down, it is OK for next ten miles or so. I drive to a small town down the line and back, by the time I hit my drive, it is about ready to drop again.

matteo
09-12-2002, 08:00 PM
first!!! change the oil filter!! i have had
several ford p/u with the 4.9 great engine!
several years back, i had the oil changed in
one of these 10 minute ooil change places,
after about 1500 miles, my oil pressure dropped, we were about to drop the pan, when
we took off the oil filter and looked at it
i think they put a roll of toilet paper in it
in place of a filter! changed the oil and
filter and the pressure come right back up!
i drove it 100.000 miles after that! now
when i go by one of those oil change places
i give them the one finger salute!!!!!!

trap
09-12-2002, 11:27 PM
I have had oil filters fail but don't think they would cause the oil pressure to come and go. Oil pump drives will sometimes slip. Anyway no matter what it is I would not keep driving it until the problem is cured. Have seen oil galley plugs come out but that causes low oil pressure all the time. A spun, worn, or wrong size crankshaft bearing may start out with good oil pressure and keep dropping as the oil warms up. Start checking the easiest things first and keep looking.

JCHannum
09-13-2002, 05:50 AM
Thanks for all the good advice.
The Rislone seems to have taken care of it. Truck has been sitting for a year, relief valve probably gummed up.
Changed oil & filter will drive for a bit and change again. If it continues will drop pan & check pump & valve.