Step by steps, bleeding, what's next?

Bleusoge · #1 (**permalink**) 03-11-2008, 02:03 AM

Hi all, I am struggling with the braking system of my 1750 Series 2 RHD / dual brake master / dual bonaldi servos...

I finally ended up replacing the brake master cylinder by a completely reconditionned unit, resleeved from a fellow board member, still I am not sure where to go to now... here is the story:

- bled the master cylinder top bleeding screw, half a liter went through, flowing happily...
- tried putting some pressure by braking at least 150 times, very little pressure, kept the pedal down, opened one screw... nothing comes out, do it again...nothing, again, again... changed caliper, did all four...nothing...
- tried again opening one side: left front+left rear... nothing comes out
- tried opening all bleeding screws on all 4 calipers, kept pumping steadily... nothing...

I could understand a problem with a rubber line hose, but with three... and if the servos were leaking at least the fluid would be showing there and the level would be decreasing.

The depressing fact being that the level in the brake fluid reservoir barely decreased during the whole process. It makes little sense to me.

Going through the various posts on the subject here, nothing came out as an obvious possibility.

Anyone has a clue? Thanks, I left the four calipers open tonight in case gravity helps...

**gprocket** · #2 (**permalink**) 03-11-2008, 09:50 AM

I am not certain if I follow how you are doing it but here is what has worked for me:

With a full reservior, I open the caliper bleed screw furthest from the MC (I assume that would be your left rear) about a half turn. I then attach a clear tube from the bleed screw into a bottle with a bit of fluid in the bottom. I have my assistant pump the brake pedal. I expect to see a lot of air coming through for quite a bit (usually it takes longer than the assistant cares to pump). Finally you will get some fluid. At that point I'll have them hold the pedal down completely and then I will close the bleed screw. Then I go to the opposite corner and repeat. Then it's back to the right rear and then finally the RF. When complete you should feel a little resistance but still far from acceptable. BTW, keep your eye on the fluid level and don't let it get sucked dry.

With everything closed off pumping the pedal should result in some level of firmness. This indicates that there is air is in the lines which is logical. Repeat the bleeding procedure above until you get nothing but fluid running through the clear line.

Now, if you are saying that you pump and you are getting no fluid at all then either either the MC pistons are positioned incorrectly or the MC seals are not doing their job. The easiest thing to do is measure the distance from the centerline of the MC rod yoke back to the first mount hole centerline. This should be 150 +/- .5mm in the relaxed position. If everything is good there then I would suspect that the seal between the pistons and bore is bad allowing fluid to pass. There is also a brake pressure differential valve that is a pain and can make it difficult to bleed but that should not prevent fluid from passing.

There are a of number of excellent posts by Jim Neill (Papajam) on the tandem brake MC and the BPDV -do a search and read those carefully.

Good luck!

**gprocket** · #3 (**permalink**) 03-11-2008, 07:35 PM

Here is the post with the diagram for the brake master cylinder:
GTV brake balance thingie.

and here is a great thread explaining the tandem brake cylinder: Tandem Brake Master Cylinder...how it works

Bleusoge · #4 (**permalink**) 03-11-2008, 08:28 PM

thank you for your input, but actually "we" using RHD vehicle (in Australia) inherited with the Bonaldi MC which is different in principle from the one shown on the various pictures. It is composed of o rings with a square section (?) instead of the conventional used in US cars, see here this might be clearer...

Identifying master cylinder and...seals!

Note the comment by Papajam and note that the pictures show the wrong seals I first put before replacing the MC, centreline provided them thinking it was a US model...

**gprocket** · #5 (**permalink**) 03-11-2008, 10:04 PM

Ah, I see. This is a very different beast indeed and I am way off the mark. Perhaps you need to go back to the person who rebuilt it and see if they have any insight. I would still say that if you can pump the pedal but are building no pressure then the issue is with the master cylinder and not the rest of the system.

Am I correct in thinking that this is a standing pedal arrangement? Can you post pictures of the actual unit?

Clayton105 · #6 (**permalink**) 03-11-2008, 10:38 PM

Bleed the master cylinder first by disconnecting the lines out (can be messy), then the boosters as I describe in this post:

Bleed 105 boosters!

And then the brakes as per usual...

Note that there are some differences between the seals in early and late Bonaldi M/Cyls. If you can't get fluid through the M/C, then your mate may have used late seals in an early cylinder.

**Chris1750** · #7 (**permalink**) 03-12-2008, 04:26 PM

Like you Bleusoge, I also have a 1970 1750GTV - probably your sister car, same colour too. Similarly, I had problems with getting rid of the airlocks in these arcane twin booster systems. I was running out of mates who would do the pump thing while I went caliper to caliper yelling 'push 'er down - hold - let 'er up' so I bought a power bleeder. Having looked around I found a guy in Sydney (member of Club Lotus) who privately sells the Motive Products Power Bleeder (Motive Products Home) for about $A175.00. His name is Elliott Nicholls and his contact details are nicholls37@zonnet.nl or Ph 0409 668 280. He is a really nice guy and was very helpful when I rang him to talk about the product.
Since I've been using it (about 18 months) I've had very few problems - occassionally I have to bleed the brakes over a weekend, once Saturday and again Sunday after the residual air 'settles' overnight, but it is nothing like the hydraulic trench warfare I was experiencing. My wife and kids say that my 'garage language' has actually improved also.
As I change my (and now my mates') hydraulic fluids every year, it's a couple of hundred bucks well spent when you consider the time and stress saved .....
Hope this helps,
Chris

PS: I don't have the bleed nipple on the master cylinder that everyone talks about.

Bleusoge · #8 (**permalink**) 03-16-2008, 04:06 AM

Hi and thanks to all your input. I replaced the MC with a completely refurbished one (resleeved) and here are some pictures of this specific type of MC for our US members (and for Centreline education in the matter!), See how specific the seals are.

Seems the MC is ok, so next step is replacing the flexible...

Bleusoge · #9 (**permalink**) 03-27-2008, 04:31 PM

An update to thanks all for the various and helpful input received and to leave a complete thread for further use by fellow alfisti.

Changing the MC for a resleeved unit was the first step, then changing the 3 rubber flexible hoses the key factor... It instantly solved most problems and mysteries, bleeding not perfect yet, but getting there and at least the way the system works now makes sense, I suspect a collapsed internal wall made me lost days!

I did a quick rebuild of the four ATE calipers over the week end, thorough clean, new seals/dust boots, but expect to have to work on them later as pistons probably need a new surface treatment. Not pitted at all but chrome plating have disappeared at 80%.

A question there, would a light grinding (Dremel type) of the cylinder external lip, above the seal would prevent further seizure and what type of grease compound would you use if any (type, not brand as in Australia US products might not be available)?