Hydraulic System

[Dave Larnder]

Hi All

I am posting this on the General TR Technical forum (as opposed to TR3A) because I want as many opinions as possible.

I intend changing my hydraulic oil throughout the brake and clutch systems as it has been in a long time now and I think the Dot4 is hygroscopic, and effects the spec.of the medium.

I have bled systems before and have the correct equipment but have never tried to drain the lot out before, so my question is :

Do I drain the fluid from all 5 slave cylinders completely first, and then begin to refill from the furthest point with the brakes and then the clutch afterwards? or do I do it like a normal bleed method? If you do it the second way, how do you know when all the old fluid is out, before replenishing with the new fluid, using Dot4 type again, to avoid any contamination.

 

Dave

[RogerH]

Hi Dave,

do it as per a normal bleed (to avoid airlocks etc).

The system holds way less than 1Ltr.

If you flush 200mL through each corner that should sort it

 

So use a full Ltr and that should ensure that all the lines are refreshed.

 

Roger

[Waldi]

If you use a clear plastic hose that fits nicely on the bleed nipples, ending in a glass jar, you can see the fluid getting clearer while you replace.

Waldi

[Nigel Triumph]

Once you've changed the hydraulic fluid, try monitoring the moisture content with an electronic test pen. There are lots on Amazon and eBay, for less than a tenner.

 

Nigel

[Will]

Rather than a glass jar, why not a plastic water bottle with an interference hole in the cap for the hose. Then some wire around the neck which you can hang on to whatever. Saves mess.

[RogerH]

Rather than a glass jar, why not a plastic water bottle with an interference hole in the cap for the hose. Then some wire around the neck which you can hang on to whatever. Saves mess.

Plus a very small vent hole in the cap - otherwise KerBang splat.

 

Roger

[john.r.davies]

There are a number of "single-handed" brake bleeding tools about. The cheapest is a length of plastic tubing, on ened of which goes over the brake nipple.

The other goes into a waste collecting bottle, and has a one way valve. This is a short length of rubber tube, bonded to the end of the plastic, with a ball bearing stuck into the bore.

You could make your own, but they don't break the bank. EG: http://www.halfords.com/workshop-tools/tools/hand-tools/europat-vizibleed-brake-and-clutch-bleeding-kit?cm_mmc=Google+PLA-_-Tools-_-Hand+Tools-_-321141&istCompanyId=b8708c57-7a02-4cf6-b2c0-dc36b54a327e&istItemId=miaxrp&istBid=tztx&_$ja=tsid:94971|cid:865695754|agid:42483195983|tid:pla-331463649838|crid:203186066553|nw:g|rnd:13115018681220135895|dvc:c|adp:1o1|mt:|loc:1006854&gclid=EAIaIQobChMI9Yrxm4St2wIVA4fVCh3GCgYxEAkYASABEgJ7dvD_BwE

 

I arrange a base plate for the collecting bottle, so that it can sit on the ground and not fall over, and extra length tubing, so that it can be placed in my view as I press the brake pedal, even the left rear (RHD car).

A useful gadget here is a broom stick with a notch in the end, so that I can pres down on the pedal by hand while standing alongside the car.

Once I see no more bubbles in the tube, I can release the pedal, move to that wheel and close the nipple with no risk that air will be drawn back in before I get there.

This allows rapid and effective bleeding.

 

More expensive devices either pressurise the master cylinder, a recipe for Brake Fluid Armageddon in my hands, or suck on the nipple as you loosen then tighten it - I don't have enough hands.

 

Of course, if you have a willing volunteer, none of this is necessary, as you can just open the nipple as your lovely assistant presses on the pedal, close it when the bubbles stop and mop up the spilt fluid later.

 

JOhn

 

PS Rogers advice to use a full litre of fluid is doubly good. Once open, even a re-closed bottle of Dot 4 or 5.1 will absorb water, and should only be used for emergencies. Throw away a bottle with dregs. Always bleed with a new freshly opened bottle.

Edited May 30, 2018 by john.r.davies