Prime power steering line on MF 85?

Tophers_Farm · Apr 10, 2021

I flushed the hydraulics on my MF 85 (it was contaminated) and drained the power steering pump lines and cylinders.

The power steering pump draws hydraulic fluid from the trans reservoir, but I think there is still air in the power steering lines/cyclinder.

Anyone know how I would go about priming the lines cylinders?

I know the pump still still works because power steering kicks in every now and then.

Would love some help!
(FYI the power steering is not at all like the more common MF 65...)

Steve@Advance · Apr 10, 2021

Was it working before you drained and flushed it?

If no, then there is another problem.

If yes, try cracking the pressure line from the pump until you get solid flow. Be careful, it may be under a lot of pressure.

Some steering pumps have a filter inside the canister, it may be clogged.

Dieseltech · Apr 10, 2021

The 85 I had would sometimes need the pump/cover assembly removed to clean the pump inlet strainer, my guess is it's plugged, no oil in means no oil out. System is self bleeding IF the pump works..

Tophers_Farm · Apr 10, 2021

I'll check the pump and filter again...
It's hard to think the pump would stop working with such a simple design.

Dieseltech · Apr 10, 2021

If the steering assist only works with engine speed higher, and not at low idle speed that's a good sign the pump is shot. Last I knew they were close to one grand for a new pump. Also, be aware the 85/88/S90 all used the same pump, BUT the drive gear on the S90 is not the same as 85/88 drive gear. MF changed the tooth angle..

lugnuts2030 · Apr 10, 2021

The power steering pump also needs enough pressure to apply pressure to hold clutch disc in pto. Their was a red light on dash that would light up when pressure is low and danger of pto clutch burn out. But light was not on all of production. Same pump for both functions. The last 85 I had I replaced that switch with a pressure gauge because switch was shot and new one not available. Service manual will tell minimum press required for pump out put. their should be a pressure switch fitted near hyd filter just forward of battery on left side. Look up pressure required, Its less than a hundred psi if i remember correct. A low pressure air gauge will work. Be sure to look up min psi required, this will test pump pressure to avoid more costly repair. Its a few minute procedure. No priming is required.

Dieseltech · Apr 10, 2021

The Power steering pressure relief valve is in the clutch housing area, the PTO pressure control valve is in the front trans cover. The PS RETURN side is used for the PTO, and the trans front cover controls that pressure to about 150-200 PSI and dumps excess to sump. The dash light would come on below 120 PSI. When the PS pump won't steer at idle, the PTO can end up with burned clutch plates too over time.

Tophers_Farm · Apr 12, 2021

Update: I removed the pump and the strainer is gone!

I threw on some mechanic gloves and fished around the trans and there's nothing there.

The strainer already had a hole in it so I'm assuming it disintegrated and went threw the pump.

I'll remove the filter and see if I can flush the line. Anyone know where I can get rush delivery for a strainer?
The 85 could be pulling harrows 24/7 right now...

Tophers_Farm · Apr 12, 2021

So the strainer does not appear to be sold separately from the pump which is over 1000$

Looks like this will need to be a custom job, I think I can remove the strainer plate and weld something similar to it (lucky to have genius welding shop next door) any advice would be appreciated. If I'm not mistaken the strainer was approximately 3 inches long?

Prime power steering line on MF 85?

Tophers_Farm

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