I need some help. I have a 90 Bronco, 189k. I've changed oil pumps and screens twice. I've had the side covers off and have run diesel through the engine to clean it out. Engine oil pressure is normal at idle. It also holds pressure with low speed driving around town. But after highway driving at higher rpm, or just driving extended periods of time, the oil pressure suddenly drops when you come to a stop and smoke starts rising from under the hood.

You then start to hear the lifters tick.

After it sits awhile, everything is normal and i start back over again going through the same ordeal.

Any information at all would be helpful, as school is right around the corner.

-Anthony

 

Is your engine sludged? If Auto-Rx is everything I hear it is (and I am trying it out now to find out), then it may be your ticket if sludge is blocking your oil pressure. Probably worth a try, but read up on it first so you know what you are doing.

 

No, I don't believe so. But there seems to be a return passage somewhere that is blocked. The pan was down and cleaned when the new o.p. and screen were put on. The valve cover was off and the return passages on both ends of the head were drill brushed. Afterwards, 10/20 wt, was run for very short period, to carry away any debris. Ditto the diesel. I had the lifter covers off and the block looked great.

Thanks,
Anthony

 

Anybody have an idea whats going on with this truck? An Auto-Rx treatment might do the trick, but that takes a couple thousand miles.

 

do u have a pcv hooked up? is ur pcv in good shape? do u have the breather oil cap?

 

Yes. PVC was changed last week. What is your theory concerning the pvc.
I'm linterested in any angle anyone has.

Thanks,
Anthony

 

my theory on the pcv was shot down by u having changed the valve, reason being, i was wondering if it was building too much preasure at higher rpm, making not want to pump oil at a good pressure. it almost sounds like a clog somewhere, what kinda shape are your valves in? are u 100% sure its not a clog? it almost sounds like a clog in a return. you know, oil comes up, can't come back down to the pump, burns off in the top end, which makes ur smoke. since oil can't get back down the oil pressure goes down.

edit:
btw, i think we all are ***-u-me-ing that you did change the oil filter.

i know at wal-mart i have seen some stuff to de-gunk the inside of an engine, u put it in ur oil right before u change the oil. u let the truck run til it is at running temp for i think about 5 minites then drain the oil. u don't drain any of the oil out before adding this stuff.

also are u sure this thing is not overheating.

i know the oil filter question and overheating question are stupid and almost assinine, but i figured i would cover all bases, and u are sure the temp gauge is not lying to you... overheating will make ur oil pressure drop, if u have something pouring from under ur hood it could be steam. i know the edit is a bit assinine but like i said, i wanna cover all basis.

 

I agree its summer and thats when things start to go wrong, I'm saying this cus I know how the heat plagues a motor and all the components- 2 motors gone down because of....I have a 73 6 banger and I can't get it over 55 mph, if I do it will suck all the oil out of the pan and I've been through everything that I could possibly think of and I still have the problem.

Bigger oil pan is my conclusion for my prob...but havn't donr it yet to see if it helps.

 

burtoby and luvinford, what grade/viscocity oil are guys runnin? just curious



also, luvinford, i don't see how a bigger pan will help u

 

Thanks guys,
Yes, the filter is always changed with the oil. The t-stat is a 160 degree unit,
and the cooling system is fairly new (pump, hoses,radiator, etc.).As I said in prev. post, everything has been cleaned internally.
I'm using 30 wt. oil. I always have. So did my dad when he drove it. Whatever the factory called for , that's what we've used.
However, I'm ready to switch to 20/50. Does anyone have any exp. with this wt. on high mileage 300's? Pro's ,con's ?

Thanks,
Anthony

 

burtoby, i would try a lighter oil before a thicker oil, try running some 5w-30 or 10w-30, that might free stuff up or just flow through the system better. your problem seems that the oil is not returning to the pan, thus your oil pump can't pump it again, which puts ur pressure down, the fact that the oil is stuck up top is why u get the smoke, the reason it does it more at higher rpm is cause it pumps more oil at higer rpm. try running some 5w-30 or 10w-30 with a good oil filter such as a fram tough gaurd code would be TG8A. also are u sure that your oil pump is seated in properly? An oil pump that is not seated correctly can do funny crap with oil pressure.

 

I run 10W30 and I change filter/oil evertime I have a headache lol witch is about once a month - it's my work truck.

I thought about it as in if it's taking oil out of the pan faster than it's getting put back in , maybe, just maybe the bigger pan idea would allow me to run at 65/70 mph instead of the 55mph because I know it will do 80 or more- with foot to the floor, lol.

Any idea on getting more mph without sucking oilpan dry??

 

This isn't a common problem, so you shouldn't have to resort to a bigger pan to solve it. You need to find out why it's happening and fix it.

There are 4 basic causes of this.

1. Plugged oil return holes in the heads.

2. Crap in the oil pan that is sucked up against the screen at higher RPMs, thus cutting the oil flow off.

3. Something compromised in the oil pump.

4. Excessive bearing clearances that bleed off a lot of oil pressure when the motor is hot and the oil is thinner.

Now, the weird things that contribute. Any chance that the head gasket is on upside down or backwards?

Do you have a high volume oil pump? High volume is different than high pressure. It could suck the pan dry before the oil can return, and is generally not recommended because it tends to wash out bearings.

I wouldn't use 30 weight oil. I'd use a multi blend. 10-30 winter, 10-40 summer. 20-50 is just too heavy unless you live in the tropics or the desert.

Like someone else mentioned, make sure the oil pump is installed correctly. Also, I've heard stories of warped oil pump bottom plates that leak pressure, and the famous Melling is among these. This would be more pronounced when the motor is hot and the oil is thinner.

 

I would say you most likely have a bearing problem - this is a common symptom for worn bearings.

Pressure is fine when the engine is cool and then you warm-up and pressure goes down - main and rod bearings are worn. The warmer the engine gets the more clearance you get in the journals and less pressure you maintain.

 

mmm well the motor did the same thing before it was rebuilt completely - but then it had issues at that time lol 2 pistons with broke landing rings ,,,,,,,,,It is rather a headache to figure it out but so far it gets great gas milage and never gets hot or even close to hot, the temp stays at about 1/8 of a tank to give ya an idea of where it reads at, right now it's 100 degrees of the day and it barly gets to where you think anything of it a ever running hot, and yes thier is a thremostat in it - new.

I have said the hell with it till it slings a rod out the side or bustes a cylinder wall

the motor is awesome and it has great oil pressure too, Imma thinking they gave me a high volume oil pump instead of the stocker one. paid for stock one anyways <--this was my conclusion to why the sucking dry part, but wouldn't a bigger pan increase my chances of it not sucking it dry @ 55 mph?? If I do 53mph it's fine all day long, but if I do 54 and up it sucks it dry, no oil leaks or consumption stays full at all times,,,