245 Brake Bleed

Stoonly

Hi all,

OK. so not my first rodeo! I've bled enough brakes in my time but……I cannot get a peddle for love or money!

It's had new rotors, pads, master cylinder, stainless hoses, apart from normal brake feel with worn discs and pads the brakes were ok before the refurb, there are NO leaks anywhere in the system, they seem to be bleeding all the air out and running clean fluid, but when the engine is running no pedal, the booster is good, operating as it should, I've bled them as per the Haynes with the double bleed on the fronts??? nothing, WTF am I missing????????????????????????????

jamesinc

Did you bench bleed the master cylinder?

Stoonly

Hi James, Yes I did mate, should have mentioned that! bled the beejeebers out of it! after I put the new hoses, pads and discs on it I bled it but couldn't get a peddle so thought maybe I had stuffed the master cylinder pushing it too far empty so put a new one on, still the same, run out of ideas! not being a quitter sucks sometimes.

And by the way tried bleeding it with a vacuum pump, a pressure pump on the reservoir and the traditional 2 person method, only method I haven't tried is gravity, that may be next before I torch it.

ramrod

Does pumping the pedal a few times build enough pressure to harden the pedal?

There must be trapped air somewhere

Stoonly

Thanks ramrod , I agree but I would have pushed a couple of bottles of fluid through by now?

ramrod

Are you bleeding fluid from all eight bleed points?

Six front, two rear

The rear proportion valves can trap air too

Stoonly

yes, doing all in the right order

ramrod

The best tool for bleeding a 240 is the pressure bleeder.

Try again with 15psi, I find order of caliper bleeding isn’t as critical as people think. Especially on this model. Watch for air bubbles, the bleed nipple threads can let air in during the process. Grease on the threads help seal

Stoonly

Thanks Ramrod, I did find the pressure bleeder better but then it stopped holding pressure? I thing my cap is faulty? I'll fix the cap and revert back to pressure bleeding and I might swap the nipples out for new ones as I thought the same thing that the nipples are letting air back in? its not gonna beat me!

Anthony

One wonders about the little distribution valve, inside left hand guard where all the pipes connect too.
Pull the little boot off the centre switch and Look careful for any weeping.

Like you said not your first rodeo, but even if a few bubble are somewhere the pedal should be at least a bit firm halfway down. Other than above valve being jammed, the new master cyl would I'm afraid be next on the suspect list.

ramrod

If that distribution block is leaking, I have a new one I would part with

John_Fraser

Is the "distribution block" the brake failure sensor? It does not allow any exchange of fluid between the two circuits. It has a small piston in the middle that detects a difference in pressure between the two circuits. The piston triggers the brake failure light in the dash.

Loss of peddle pressure with engine on might be booster push rod adjustment. Too much clearance between the rod and MC piston takes up all the peddle travel. I believe the clearance should be 0.030".

Slowbrick

I believe you probably have an airlock in the rear proportioning valves. The 245 I have always gets an airlock there when ive done major brake work. What gets it moving is to use a pressure bleeder, open the rear brake bleeders and while its pressurized pump the pedal slowly to get it pushing the air out. Another method I used to use before I owned a pressure bleeder was to use a vacuum bleeder, lock it on and press the pedal slowly to get things moving. Its frustrating that is for sure. Bleeding a 240 with a dry brake system is not exactly trivial and dont feel bad if you are struggling with it. The amount places for air to get trapped is pretty significant.

Stoonly

Hi Everyone, thanks for all your input, just waiting on kits for the callipers atm, then it will be the distribution block and or the rear proportioning valves which I too suspected? the car has been off the road for 12 months so I pulled a calliper apart because I noticed they were'nt moving at all , they were really dry, a bit of surface rust not perished just dry! they're not original and looks like a reasonably recent replacement still nice and passivated bores and pistons clean, so I'll rebuild those and carry on, I do have a pressure bleeder slowbrick thx, keep you all posted!

Stoonly

So, I have brakes again!!! thank everyone that chipped in. Not sure what the problem was, after rebuilding the calipers and also pulling out the new master cylinder and bench bleeding again to double check that??? I put it all back together and pressure bled the hell out of it, I now have a peddle. I don't think I've had a system so reluctant to bleed, so to everyone out there going through the same thing just push on you'll get there.

On a related note anyone know what the front/rear bias is 70/30, 80/20?

ramrod

Patience and time spent always pays off

Congratulations

I don’t know if there is a specific number for the brake bias, you are in the right area by guessing 70% to front.

Stoonly

Thanks Ramrod, reason for asking, I have the car up on stands with no wheels on and when i run it in gear and brake the rears don't seem to pull up much, no a good test I know and the pads need bedding in but wonder are the proportioning valves good? can't imagine they would both be faulty though? I'm sure all will be revealed when its back on the road!

Thanks again.

dmc

proportioning valves do fail after the many years they have been in service.

a simple test, once driving, is to take it for a drive and heat the brakes up a little. not heaps though make them work. once back in the workshop or driveway measure the temp of the rotors. i have a handheld (infra red?) thermometer i point at the rotors and it tells the temp. i think the last time they were all about 90 deg. if one is down you will know. i had one at 50 deg once, proportioning valve swapped, all good :-)

pretty sure the thermometers are cheap if you look around, like $30 from jaycar or so.

Stoonly

Thanks dmc, good advice and an easy check! I'll definitely do that.