Bleeding Hydraulic Transmission Lines

[reynolds.brad]

Hi all,

Has anyone ever had to bleed air out of their hydraulic transmission lines?

I've just finished replacing the damper/drive plate on my Ford Lehman 120, have put everything back together and low and behold, she won't go into gear.

I'm pretty sure there's a tonne of air in the lines but I'm having trouble bleeding it out.

Has anyone done this before? is there a trick? how long did it take you? Did you have a bleeding nut/screw etc when you did it?

[skipperpete]

Usually there is no need to bleed the cooler lines, they drain at every shutdown anyway.
Did you replace the seal on the front of the gearbox? If the pump cover goes back on in the wrong position that can cause no gears. Also if the new plate puts pressure on the gearbox input shaft, no gears and very noisy.

[reynolds.brad]

Hi Skipper Pete, Thanks for the info!

No I didn't change the seal. I just put the gearbox back in (I thought) just as it originally was placed.

I was convinced the lines needed to be bled so now I have no idea what's wrong :-(

It was originally taking a little longer than I thought it should to kick into gear but now it's not going into gear ever!

I'm stumped!

How do I check to see if the new plate puts pressure on the gearbox input shaft?

It doesn't sound noisy in any strange way...

[skipperpete]

If it's exactly the same plate and it's not back to front it should be ok. If the gearbox is a Borg warner velvet drive it's time to do a pressure check on the ahead astern clutch packs at the external ports and potentially service the selector valve.

[a64pilot]

You sure it’s full? Sorry had to ask but sometimes it’s just a level problem

[reynolds.brad]

Hi,

Pretty sure it's full yes. I've checked the dipstick level a bunch of times and it seems fine.

I should mention that I accidentally poured a lot of fluid down the breather hole instead of directly into the dipstick!

(the breather hole seemed more logical to add fluid too to a novice - oops)

I separated the rear assembly to drain all the fluid out from the breather hole mishap and then added fluid again down the dipstick and checked the level. I'm wondering if I've clogged up some stuff that should't be clogged up.

I've attached a Paragon trouble shooting PDF which mentions 'cleaning lines and passages' but I have no idea how to do that?!....Take the box out again and turn it upside down?

I'm also trying to get the relief valve out to clean but its pretty stuck in there and seems like I need some kind of surgical forceps to get it out.

I wish I could afford a mechanic! This sucks! lol

[skipperpete]

Hi Brad
Sorry for going off on a tangent about Borg warner transmissions, it never occurred to me that you might have a Paragon, an oldy but a goody in the world of ancient marine gears.
Paragon made excellent gearboxes and they were used in forklifts and fowler cranes. What oil are you using in the Paragon? It might be worth overfilling it temporarily, no harm will occur as long as the level is reduced before going back into normal operation. Somehow it needs to be established whether there is any oil pressure in the system and what that pressure actually is. It might help to remove both cooler hoses and either run them into a bucket or loosely join em together and briefly run the engine ( or just crank it over) to see if there is any oil flow from the lines. I actually rebuilt one of these once but have rarely encountered another since then...... in fact I've had 2 of em sitting under a bench in my workshop for more than 10 years now, one with a vee drive and the bigger one off an early model ford. I'll drag the ford one out later and see if I can find any gauge ports or other clues that might help you to solve the mystery.

[reynolds.brad]

Hi Skipper Pete,

I'm glad to hear it's a good gearbox :-) No problems about any tangents lol I'm stoked to be getting help on here it's amazing!

I'm using Automatic Transmission Fluid DX3

I've disconnected the hoses to see if fluid is fluid is being pumped through and there is. Maybe there isn't enough pressure?

Thanks for being so helpful I really appreciate it!

[skipperpete]

Whoa[emoji844]hold the bus. I just opened up a Paragon selector and top housing and there's a few traps for young players. First..... it seems that the system pressure is delivered to the selector mechanism via the oil cooler hoses at up to 200psi so running the engine with the cooler hoses in a bucket is poor advice but using a hydraulic connector to join the hoses is still a reasonable idea.
The gauge ports are situated on the sides of selector housing, two little ⅛"bsp plugs with an internal hex to enable removal. I couldn't get either of mine to budge. If you decide to remove the selector mechanism, undo the plug next to the right hand gauge port... it releases the spring and ball of the detent mechanism that lets you feel when neutral or drive is selected and allows the selector to be removed from the housing without getting stuck by the spring. Here's 3 pics of the part.
I still have a few thoughts re the drive plate because my Paragon gear input shaft spline is not protruding from the bellhousing, it's level with the edge and if the driveplate/damper was fitted to the flywheel backwards, the gearbox spline would not engage and no gearbox rotation could occur. This is easy to check.... if you look through the 1"diameter hole on the gearbox bell housing near the starter motor you can actually see the drive plate to gearbox connection.
I hope all of this helps you to solve the problem and get underway again.

[reynolds.brad]

skipperpete...I cannot thank you enough!!

This is seriously valuable information and it's greatly appreciated

I'll let you know how I go!

Brad

[reynolds.brad]

Just so you know Skipper Pete your original suspicions of the damper plate not actually turning the gearbox was correct!

Totally should have replaced the clutch kit and gearbox seals of course - doing that now after some successful trips.

Thanks for your help :-)

[skipperpete]

I’m glad to hear that you resolved the problem and got underway again, good work!!