oil pressure problems

[ltj126]

Just bought an '88 Bronco with a 351 in it cold it runs great but as the engine warms up it starts ticking and the oil pressure drops to nothing. It has 135000 miles on it and appears to have been well taken care of. The ticking starts around 2500 rpms as it warms up and the oil pressure drops as warms up to normal operating temp it starts at about 1500 rpms and starts running rough and stalling when in gear. Any ideas where to start looking? It has plenty of oil in it and it looks reasonably clean. My wife's bronco ll with a v6 in it did this and an intake gasket fixed it any chance I'm looking at the same fix here?

 

[Krafty]

it could be a few different things,1 it could be oil pump loses pressure,2 the main bearings could be wore right out, or 3 you could be losing pressure from either a gasket or a crack in the block.

if you have a bad head gasket then you should be able to either see oil in the coolant if you do a flush, or see coolant at the bottom of the oil pan.(first thing that comes out when you pull the drain plug), or your engine will burn it off and smoke alot.

in any of those situations there are things you can check like coolant level, oil level which will tell you if you are losing your oil anywhere,

the next thing i would look into is replacing the oil pump.

 

[nelbur]

Actually, the first thing you should do is what is easiest. Folks seem to buy these old engines and change the oil to the 10w30 that Ford recommended for the engine when it was new. These engines are now typically well worn and must have higher viscosity oil to have acceptable oil pressure at idle when the oil is hot. That is what 20W50 is made for, and of course there are the oil thickeners if 20W50 is not thick enough. I suggest that you change to 20W50 with a quality oil filter like Wix or Napa, and see if that helps your problem. If you can manage to get the hot idle oil pressure to stay in the bottom of the normal band, you are fine. I believe the only possible down side to thick oil is that one needs to be careful to keep the RPMs modest until the engine is warm to reduce the possibility of spinning a bearing from revving it while the oil is still very cold and thick.

 

[Seabronc]

Right on Nelbur!! I have been running 20W50 in my engine for the last 3 to 4 years plus a quart of Lukas Oil Stabilizer. My formula is 5 quart of 20W50 and 1 Lukas plus a quality oil filter. A good rule of thumb for acceptable oil pressure when hot is 10 pounds per 1000 RPM. Mine does just a little higher than that. Also I installed a wet gauge since I never liked the Ford gauge, I like to be able to read it in PSI not L N H . In fact in newer Broncos, the Oil pressure gauge actually tells you nothing since it is designed to show normal unless you loose all your pressure.

Good luck,

 

[ltj126]

sounds like I good place to start thanks guys

 

[ltj126]

changed the oil pressure is good now filter didn't have much in it but was pretty heavy. still have the tick but it sounds like a rocker arm in the #2 cylinder still don't start ticking until warm and at about 1600 rpms. Still idles rough when warm but the rpms drop down from about 900 to about 5 or 600 and it surges. Any suggestions where to start looking for the cause of the surge or the drop serious drop in rpms?

 

[ltj126]

it runs very smooth cold

 

[miesk5]

yo ltj126,
Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
http://broncozone.com/topic/14269-code-reader/page__pid__74587__mode__threaded

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

And Post em here according to:
KOEO
&
KOER

 

[nelbur]

The surge at warm Idle is common on these old trucks. Since You have no problem when cold, your Idle Air Control is likely working fine. But when the computer deactivates the IAC the idle drops too low, so the computer opens the IAC which raises the idle too high so it shuts it off again, etc. etc. That is my theory anyway. If you were to clean the soot from around the butterflies on the throttle body it should improve as more air could get buy them at hot idle. Ford produced a kit to correct this surge problem which is a high dollar spacer installed under the IAC, that allows an adjustable amount of air to bypass the IAC to make up for sooted up throttle bodies. It is about $90, but you can do the same thing by cutting away the portion of the IAC gasket between the two air holes, which allows some air to bypass. I made a thicker gasket to give more bypass. This is easy to do and might reduce or eliminate your surging problem.