Anyone running 4 pots? I hope I don't, have issues... Options

[rick 918-S]

I installed 4 pistons front calipers and a 19mm master cylinder this weekend. Also removed the "P" valve for the rear calipers and installed a "T" fitting. So the lines were pretty much empty. I added ATE Super Blue fluid and bled the system until I used a quart of fluid. After a day of hunting I managed to locate a friend that had a new quart on the shelf. We continued to bleed the system and added another half quart.

Here's the my issue... After bleeding the system for several hours I still have a low peddle. After the second pump of the peddle the hieght seems good. ( goes from 2/3 sweep to about almost 1/2)

Do you think I need to continue to bleed the system or are the 4 piston calipers requiring the extra motion just to fill?

Anyone running 4 piston calipers with a 19mm master cylinder?

If so how much peddle travel do you have?

[94teener]

Run it as is for a day or so, then re-bleed. Always worked for me.

Phil

[John]

You are going to need to move much more fluid now with the 4-piston calipers.

Search for a 23mm master cylinder. It is an ATE unit and almost bolts in. (You either "dent" the front axle tube or grind on the new master cylinder. We opted for the denting of the axle tube.)

There is a source for these on the web if you google search for (i believe) 23mm master cylinder....
I think the ATE # 3.2123-1003.3.

Perhaps others know about this?

Our race car had a low pedal and I had read about the 23mm master cylinder many years ago (in an old UpFixen) and we did find one recenty (within the last two years) and it is MUCH better!

Look for it, find it, buy it, install it, LOVE it.

Just my $0.02.

[Jeroen]

Which 4pots are you running?
Front & rear, or just front? What are you using in the rear?

cheers,

Jeroen

[seanery]

Yeah, what are you running in the rear?

Yes, you will need to bleed, bleed, bleed and then bleed some more, it'll take quite a while.

[rick 918-S]

Thanks all, I installed BMW 1974 2002 4 piston calipers in the front, 19mm master, "T" fitting in the rear in place of the perportioning valve, and stock 914 rear calipers.

I had to get creative with the lines going to the front calipers. Early BMW 4 piston calipers have two lines per side running from the master to the front calipers. I hope this isn't causing issues.

[John2kx]

Rich,

I don't have 4 piston calipers but would recommend using a power bleeder (bug sprayer type) before giving up. Heard all the problems 914 folks had with bleeding even stock brakes and gave this device a try. By myself, it only took about 20 minutes and my freshly installed "dry" brake upgrade worked great. Did it a second time just for kicks. With the pressure gage on this device, you would be able to detect leaks fairly easy.

Pedal travels about 1/3 stroke before pressure builds.

(M calipers up front, stock but widened in rear, T removed, s/s lines and 19mm m/c.)

John

[Joe Bob]

Tapping with a rubber mallet also frees up bubbles....

[davep]

Are you using both bleed nipples on the caliper? When the feed is only on the inside, the outside pistons are very hard to flush the air out.

DaveP

[Mountain914]

I've got 4 pots on 4 corners each. But.... went with the 23mm MC.
Anywho - You probably want someone who owns the same type calipers to reply (mine are Wilwood). But you should never have a soft pedal - regardless of MC size (right?).
So keep bleeding...

[Brett W]

Guys those are not BMW calipers they look like Girling Calipers off of a 240 Volvo. They have the same twin line setup because Volvo had 4 lines running from the master cylinder to the front brakes.

[3d914]

Rich,

If the nipples are anything like those on the teener, you are probably getting some air bypassing the threads of the nipple. I was spending a rediculous amount of time and not getting anywhere. Mechanic friend suggested putting a dab of grease around the threads to stop the air getting by.

Worked like a champ. Too easy!

Good luck.

[banderson]

Venting Clearance, Venting Clearance. Did you check it? And use 1/2 of the book spec?

Is the piston area more than the 320i calipers? If so, your rears may be undersized. Consider puting the stock fronts on the rear and installing an APV. Who uses a parking brake anyway?

[rick 918-S]

Guys those are not BMW calipers they look like Girling Calipers off of a 240 Volvo. They have the same twin line setup because Volvo had 4 lines running from the master cylinder to the front brakes.

These are ATE 4 piston style from a BMW. U had a set of Volvo calipers. They are even bigger the ATE units pictured.

[rick 918-S]

Venting Clearance, Venting Clearance. Did you check it? And use 1/2 of the book spec?

Is the piston area more than the 320i calipers? If so, your rears may be undersized. Consider puting the stock fronts on the rear and installing an APV. Who uses a parking brake anyway?

What's the book say? Can't find mine... (IMG:style_emoticons/default/sad.gif)

[rick 918-S]

I'm going to let the car sit for a week or so while I push a few things forward. Then I'm going to borrow a garden sprayer set up a friend of mine used to bleed his VW Thing. Then I'll know if I need to change things.

[jdogg]

I had a similar problem this weekend, new 19 mm m/c. I couldn't figure out how to bench bleed it without making a huge mess, so installed it dry. After bleeding at all the calipers, I still had to pump the pedal to get any pressure (air still in there), so I bled it at the master cylinder by just cracking the connections (what a fucking mess), then did the individual calipers again. Have a nice firm pedal now.

[Mueller]

I guess we are not the only ones using those 4-pot calipers...here is a site that has drawings for making an adapter....

4-pot adapter -dual circut

[andys]

I've got 4 pots on 4 corners each. But.... went with the 23mm MC.
Anywho - You probably want someone who owns the same type calipers to reply (mine are Wilwood). But you should never have a soft pedal - regardless of MC size (right?).
So keep bleeding...

Lee,

Can you describe how you plumbed the Wilwood's? Specifically I'm interested in how you went from the 1/8-27NPT to the Porsche hard lines. Did you do the adaption at the calliper, or at the flex to hard line? What brake line adapters did you use?

Thanks,

Andy

[Brett W]

I stilll have the Volvo, calipers the pictures are just deceiving as to the real life size. My bad. I have kinda leaned away from using the Volvo caliper because of the weight. The are really heavy. I was running BMW calipers when I wrecked the car and was really happy with them then. I would find a way to run something like the Wilwood Dynalite or Superlite. on the stock mounts and just get some hats from Coleman or the like and run some meaty ass rotors.