MF 7495 Vario problem

[Farmer_Joe]

The pressure sensor is the next thing to check. Nearly £400 a piece though!
Then I think the clutch valve is about the last thing there is left to check.

ouch, that's dear, any other source for it? well worth a check i saved over £200 recently vs mf on viscus fan coupling, took some internet searching and a helpful forum member though!

any chance its also anywhere else on the machine to swap?

 

[Bumble Bee]

ouch, that's dear, any other source for it? well worth a check i saved over £200 recently vs mf on viscus fan coupling, took some internet searching and a helpful forum member though!

any chance its also anywhere else on the machine to swap?

There maybe another on this tractor. Failing that I'll see if our 7720 has one on.

 

[Southmec32]

Have you read the ph pressure while you are getting it to fault downhill? . Are you towing any implements while doing it causing it to hit its relief pressure . Also is this a teir 3 or 2 machine?. I am pretty sure you can read pressure on the dot matrix by holding up key for 5 seconds then going to the TC ANA page in the diag section

 

[Southmec32]

Just read your previous comment on hydraulic pressure going to 0 . Is this the loop supply pressure?. Have you done a t port test to eliminate external valves?.

 

[Bumble Bee]

Just read your previous comment on hydraulic pressure going to 0 . Is this the loop supply pressure?. Have you done a t port test to eliminate external valves?.

Yes that is the pressure in the loop.
If that is the test where you check if oil flows out of the t port then no. Not sure how I would do that test while driving down the road, as that is the only time the symptoms show?

 

[ih1455xl]

You need a digital pressure gauge with data logging

 

[ih1455xl]

Or a small child to hold a phone recording the gauge

 

[davidroberts30]

Hope you don't mind me resurrecting this thread again.
I've been working on this problem on and off and have still not managed to cure it.

I've replaced the Scavenging valve, swapped the forward and reverse pressure relief valves. Manually locked off the coupler valve and replaced the valve block containing all the small pressure relief valves on the right hand side of the gear box. Everything pressure tests ok apart from the lubrication pump pressure is a bit low, but that does not control any part of the gearbox but never the less needs replacing.
I'm going to try swapping some pressure sensors round.
The local dealer and MF seem a bit stumped as am I.

Has anyone any further ideas?

your wiring loom isnt chaffed or frayed about the gearbox area?

 

[davidroberts30]

It had a full service just over 200hrs ago.
Fault has only just started as far as I know.

Just been out again and had the transmission hydraulic pressure on the diagnostic screen and when the symptoms occure it seems to be repeatedly, quickly but momentarily dumping the hydraulic pressure when decelerating down a hill then increasing pressure again.

As you said earlier, it seems worse when the oil is cold I think.

its not overrevving the engine when its doing it?

 

[Bumble Bee]

your wiring loom isnt chaffed or frayed about the gearbox area?

I can't see anything obvious.

 

[Bumble Bee]

its not overrevving the engine when its doing it?

It does when it re engages drive if it has slowed down a bit. You have to be ready to press the clutch!

 

[Deerefarmer]

I can't see anything obvious.

You won't see anything obvious. Look in places where the loom is touching or draped across the tractor and check inside the loom. Wires can get etched and frayed by the corrugatioms in the loom

 

[Bumble Bee]

Or a small child to hold a phone recording the gauge

You won't see anything obvious. Look in places where the loom is touching or draped across the tractor and check inside the loom. Wires can get etched and frayed by the corrugatioms in the loom

I've had a good poke around at all the bits I can get too.
It's looking more like a new gearbox is needed. Had some info from a guy that knows and my symptoms exactly match what he was saying so going to have to bite the bullet unfortunately.

 

[daveydiesel1]

I've had a good poke around at all the bits I can get too.
It's looking more like a new gearbox is needed. Had some info from a guy that knows and my symptoms exactly match what he was saying so going to have to bite the bullet unfortunately.

Why not ring swinnerton tractors, they revamp varios and seeing as yours isnt wrecked it probably wouldnt cost too much to replace wear items

 

[Magnus Oyke]

Have you actually had anyone that knows what they're doing to look at this tractor yet?

How many hours have you spent on it and how much do you value your time at?

 

[fredf]

My son is changing the second tractor vario if you would like a chat with him send a PM to me for his phone no.

Tom.

 

[Blue.]

The pressure sensor is the next thing to check. Nearly £400 a piece though!
Then I think the clutch valve is about the last thing there is left to check.

Can you fit a tee at the pressure sensor,then fit a gauge?

 

[Southmec32]

Yes that is the pressure in the loop.
If that is the test where you check if oil flows out of the t port then no. Not sure how I would do that test while driving down the road, as that is the only time the symptoms show?

Just do the t port up on axle stands to be sure in emergency mode otherwise it sounds like you nay need and insert if pressure going to zero. It sounds like you have an internal leak in the loop.

 

[davidroberts30]

I've had a good poke around at all the bits I can get too.
It's looking more like a new gearbox is needed. Had some info from a guy that knows and my symptoms exactly match what he was saying so going to have to bite the bullet unfortunately.

Im not convinced
I think its electrical or software related

 

[Bumble Bee]

Why not ring swinnerton tractors, they revamp varios and seeing as yours isnt wrecked it probably wouldnt cost too much to replace wear items

I spoke to them today. They confirmed the likely problem as a warn bearing which is allowing the shaft to move when it is under pressure from decelerating. This then allows movement on the pressure plate and oil pressure is lost..... or something like that.
This is also backed up by the fact that the lubrication pressure is a bit low. This being caused by the oil leaking from the warn bearing housing.