HELP! Weird oil pressure issue

purple pony · Aug 22, 2010

My son's '89 Bronco II had a new 2.9 crate engine put in 5 years ago. He took it to college and put on about 50K. It developed the following problem: oil pressure is fine at idle. As soon as you put in in gear the pressure drops to almost 0. He took it to a mechanic who told him it was the bearings. This is the same mechanic who charged him $250 for new plugs and wires. Needless to say, I don't particularly trust the guy.

Wanting to get 2nd opinions from some of you guys before he junks the pony as not being worth repairing.

Thanks!

RobbieD · Aug 22, 2010

Are you going by the stock gauge in the dash? If so, there's the chance that you have an electrical issue instead. Before deciding on junking or repair, it'd be worth the trouble to put a mechanical oil pressure gauge on it to get true reading straight from the motor.

adsm08 · Aug 22, 2010

^
+1. Those gauges are idiot lights anyway.

I had a Taurus once (customer's car) that would fire right up, run fine, but as soon as you put it in R to back up, the engine would rock back just a bit, stretch a chaffed wire, and kill the key on signal so all the electronics died.

baddis · Aug 22, 2010

i have had issues with fram oil filters causing a no oil pressure problem. changed the filter and it fixed the problem

adsm08 · Aug 23, 2010

Yeah, an oil change with a high quality filter could also help. Good point baddis.

Sasquatch_Ryda · Aug 23, 2010

Get a manual oil pressure gauge and check it properly.

If you are not hearing any noises from the engine, its got oil pressure.

purple pony · Aug 26, 2010

More info

Unfortunately, it is making noise. I'm afraid it's not just the gauge. He took it to a mechanic who said the main oil bearing is bad. The mechanic also said that we can't just replace the bearing because the bearing going bad will have caused all kinds of other problems (enlarged the hole that the oil flows thru requiring a fabricated replacement). It will be WAY expensive and not easy to do in the microscopic town we live in. Do you think this mechanic is just blowing smoke or being realistic? My son only has a few days to decide what to do. He is moving out of state and we need to either fix the thing now, wait until he can afford a new engine to put in it, or sell it for parts. Advice anyone?

Shran · Aug 26, 2010

What kind of noise is it making?

If the bearings are actually bad, you should have very little or zero oil pressure all the time and a lot of nasty silver colored sludge in your oil. If this is actually the case, sometimes the engine can be saved by inspecting and/or machining the crank and installing new bearings, but it depends on how long it was run with no oil pressure.

I think you should really check the oil pressure with an actual gauge, this could be as simple as an electrical problem with the sending unit or just a bad filter like baddis said.

purple pony · Aug 26, 2010

Symptoms

The truck has oil pressure at idle. When it's put in gear, the oil pressure drops. It is just a tap at this point. The tap increases in intensity as it warms up until is a pretty good banging. My son said it sounds like metal slapping metal. He drove it for about 3 hours with it making noise. He said the mechanic told him the lifters were collapsing. (Note: this mechanic didn't actually look at anything, just diagnosed from the verbal description.) I personally have only heard it run long enough to put it on a trailer. I'm going to go start it up and listen for myself. We haven't pulled the pan yet, but that is next on the agenda if there's any hope the engine can be saved.

Shran · Aug 26, 2010

I doubt it's bearings in that case. What you are describing sounds like the typical 2.9 lifter tick - usually it goes away when the engine warms up. It's caused by poor oiling in the heads from the head design and also clogged oil passages. Sometimes it can be cured by running a detergent like diesel fuel in the oil for a bit right before an oil change.

A rod knock is about the only other thing that will make that kind of noise but it sounds like a dull thud deep inside the engine that increases exponentially when you load up the engine.

FYI when you put a mechanical gauge on it, it is normal for it to only hold around 10psi at idle... the last 2.9 I had only held like 4psi at idle and it's still going strong. The old rule of thumb is that for every 1000 RPM, you need 10psi of oil pressure - so at 3000 RPM you should (ideally) have 30psi.

purple pony · Aug 26, 2010

Got more info

Drug some more information out of my son. He's a Chemistry major, so getting relevant physical information out of him is like pulling teeth.

Apparently, the oil pressure only drops to 0 when he makes a hard turn or drops it down into 2nd.

This is sounding better and better all the time. Oh joy! There may be hope for the purple pony yet.

purple pony · Sep 6, 2010

Resolution

Well, this is really pretty funny. :icon_rofl:

My son and I took the Pony for a little test drive. Lifter noise at start-up with low oil pressure, oil pressure dropped radically when making a turn and the pressure gauge fluctuated wildly in the no pressure zone. Lifter noise got worse. :icon_confused:

Brought it in and put it on the lift. Pulled the plug to drain the oil and see what was going on with the oil. This little trickle came out. There was about a half-quart total in the poor thing. Put in a new filter, filled the oil up, started it, and it runs like a champ. Doh!!!! :yahoo:

Drove it the 750 miles to Seattle - no problem at all. Had to add a quart after 400 miles. They run way better when they actually have oil in them. My son's new nickname is "Half-Quart". Good thing he's going to become a chemist....'cause he'd sure never make it as a mechanic.

Not too happy with the mechanic who checked the Bronco out and told him his main bearing was shot and the lifters were collapsing......then offered to buy it off him for $200.

Once again the old adage that "it's probably something stupid" has been proven true. Thanks so much everyone for all your input, advice and support!!!! The Purple Pony Rides Again :icon_bounceblue:

HELP! Weird oil pressure issue

New Member

2.9l Mafia

Senior Master Grease Monkey

New Member

Senior Master Grease Monkey

Well-Known Member

New Member

Junk Collector

New Member

Junk Collector

New Member

New Member

Sponsored Ad

Sponsored Ad

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals