6v92t not building oil pressure

brettpearson67 · April 13, 2019, 10:57:07 AM

So I'm going to drive 300 miles to pick up the bus I bought, sight unseen. 1985 MCI 96A3 with 6V92T. Gotta fix a minor problem on it before I can drive it home. Too good a deal to pass up, so I took a chance.

PO says it's not building oil pressure. When it suddenly lost pressure, they shut it down and haven't driven it since.

PO said bottom end was rebuilt 3 years ago, and mechanic said very little wear on main bearing surfaces. He also said oil pump gears looked great. Bus has been very well maintained.

PO feels it is perhaps the oil pressure regulator or relief valve, or possibly something in the pick-up.

Could be a faulty gauge, but PO also said they checked line going to compressor and saw no oil coming there.

I will be bringing spares of the valves, along with filters, oil, etc.

Just wondering where else we might look for problems?

Thanks

luvrbus · April 13, 2019, 11:28:26 AM

Pull the oil pan I almost bet the pickup tube has broken or the last guy that did the bottom forgot to install the support and torque the bolts on the pump,I would not start the engine till I pulled the oil pan JMO

brettpearson67 · April 13, 2019, 12:03:44 PM

Thanks. Definitely planning I'm pulling the pan.

Geoff · April 13, 2019, 02:05:46 PM

Hey, Twisted Sister fan, I ran into a similar problem with a customer's 8V92TA and it turned out that the
crankshaft woodruff key on the oil pump gear had sheared off so the oil pump wasn't working.

You should make sure the front crankshaft pulley bolt is super tight because if it is loose the key breaks. In fact, just tightening the bolt will get the pump working again (if that is the case). The woodruff key is just a guide and is quite thin.

brettpearson67 · April 13, 2019, 02:27:44 PM

Geoff,

That's an awesome tip. I had considered maybe broken teeth on the pump gears, but not a sheared key.
Gonna make sure to bring balancer puller and check it out if regulator and relief valves are good.

Thanks!

brettpearson67 · April 19, 2019, 03:37:37 AM

So I removed the oil pan and replaced both the Oil Pressure Refief valve and the Oil Pressure Regulator, along with the pick-up tube for good measure, but still no oil pressure. Im going to go down next weekend and pull the oil pump and check it out.
Oil was flowing out of a hose connection, one where apparently it wasn't flowing from before, on the left(passenger) side of engine, close to bellhousing, when I disconnected it. Still no pressure on the guages, back or front.
If not the pump, any idea what direction to go from there?
Thanks

luvrbus · April 19, 2019, 06:21:48 AM

nothing left but the oil pump or the drive,as Geoff said the drive slides on the crankshaft into the pump and has a key

Dave5Cs · April 19, 2019, 10:21:05 AM

Passenger side is the right side.

brettpearson67 · April 21, 2019, 04:27:39 AM

OK.
I removed and disassembled the oil pump and inspected the gears. Everything lookd good. I took it to a diesel mechanic for a second opinion, and he concurred.
He suggested I replace the oil filter. I did so and put everything back together and, viola, we have strong oil pressure. Go figure.
Anyway, i plan on relocating the oil filter to a more accessible spot. It was not easy slithering underneath the engine and tranny to get to it.
Lots to do.

chessie4905 · April 21, 2019, 05:05:10 AM

I'm concerned that a plugged oil filter wouldn't allow oil pressure. I would cut it apart and inspect the debris. A lot of metal, and start inspecting bearings. Was there any debris in bottom of pan when you removed it, or had previous owner removed it and cleaned it?

brettpearson67 · April 21, 2019, 05:20:14 AM

There was debris, but it appeared to be silicone sealant from the pan(no gasket). Did not see metal. When I get it home next weekend I will cut the filter apart and see what I can find.
There was, however, a small amount (drops) of coolant in the bottom of the pan. That concerns me, for sure.

TomC · April 21, 2019, 08:53:45 AM

I had the same problem with my transit bus-the oil filter was underneath in the middle of the bus-which is fine for changing the oil over a pit, but horrible to get to any other time. Since the oil filter was already remotely mounted, I had longer oil lines made and a spin-on filter (Cummins type) mounted just inside of my right engine access door. Now easy to get to and also inspect. Good Luck, TomC

luvrbus · April 21, 2019, 11:07:56 AM

A plugged filter wasn't his problem those engines by pass the oil cooler and filter if either one becomes plugged

brettpearson67 · April 21, 2019, 11:16:55 AM

Quote from: luvrbus on April 21, 2019, 11:07:56 AM
A plugged filter wasn't his problem those engines by pass the oil cooler and filter if either one becomes plugged

Do you have a suggestion as to the cause?

I am at a loss to say what the problem was. It apparently wasnt any of the aformentioned suggestions. I did blow compressed air through the line going to the oil pressure manifold(for lack of a better word).
All I know is when I put the oil pump back together, re-installed it and changed the oil filter. I had oil pressure.

Thanks

luvrbus · April 21, 2019, 11:36:44 AM

The oil is pressurized at the pump it goes through the adapter plate since you have a remote filter I am presuming the engine has the double oil cooler which has a by pass valve to by pass incase the filter or cooler is plugged. I have no answer to why you have oil pressure now but it was not because of a plugged filter because the valve on the adapter plate will open and return the oil back to the galley lol what ever you did it worked that is all that important in the end