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Posted by: Mike's2nd914 Jul 4 2003, 04:52 PM

Hey guys, I could use a little help. I just got finished bleeding down the brake system after rebuilding all four calipers. The brakes worked when I started this project but I had one (or more) calipers that were frozen. Now, the calipers all work great and I believe I have bled all the air out of the system but there is still way too much travel in the pedal and I have to pump the pedal a couple of times to get any brakeing. What's up? It took about a month and a half to get everything rebuilt during which time the car sat up with little or no fluid in the brake system. Could the master cylinder, that was working fine before this, could it have gone bad just sitting there?

I appreciate any help or suggestions!

Posted by: Porsche Rescue Jul 4 2003, 05:49 PM

If you have to pump to get any firmness in the pedal you have air in there. I would bleed again. Also I have had major improvement by bleeding the proportioning valve (on the firewall under and in front of the engine). Crack the fitting of the outlet line (wrap a rag around it to catch the fluid) while the system is under pressure just as if you were bleeding a caliper.

Posted by: Aaron Cox Jul 4 2003, 06:04 PM

bleed the brakes again. theen try ATE super blue also.

Posted by: Lawrence914-6 Jul 4 2003, 06:35 PM

I'm assuming that when you bleed the front, you're jacking that end of the car high in the air... then letting it down, and jacking the rear up for bleeding.

If the brakes aren't too bad, and you can drive the car safely... then drive it around the block a couple of times, stopping frequently. Then rebleed. It seemed to help mine.

Air can get trapped in the proportioning valve - try rapping that gently with a rubber mallet, especially while having an assistant pump the pedal.

Also, if that doesn't work, you can try to crack the line at the top of the proprotioning valve, and bleed any air from there. I've never had to do that, but some people claim it works for them.

-Rusty

Posted by: Mike's2nd914 Jul 4 2003, 06:35 PM

Thanks for the suggestions. Please, anyone with more please share them! I put the whole car up in the air at once and bled Right rear, left rear, right front, left front in that order. Also bled the master cylinder by breaking a line at the cylinder. That valve in the rear may be part of my problem as I totally drained the brake fluid and replace it with new (along with new SS lines at the cylinders). I guess I have some air trapped in there somewhere.

Posted by: tat2dphreak Jul 4 2003, 06:54 PM

definately sounds like air in the lines to me... I had a heck of a time bleeding mine... the prop. valve is the key, or at least it was to mine... treat it like a 5th caliper! also... as good as mityvac type tools are... they aren't as good at finishing the job as the 2-person method IMHO. get it bled as good as possible, then draft a friend, or one of your kids to pump the brakes for you.

good luck!

Posted by: nealnorlack Jul 4 2003, 07:17 PM

Hi,
I had exactly the same situation with my 911. I rebuilt everything but the master cylinder. The problem is when there is no fluid around the seals in the master cylinder, the seals will dry up and shrink. It sounds like your system went without fluid in it for some time. Rebuild or replace the master cylinder, maybe with a 19mm one, bleed the system again using the tips in the previous messages and it should work great.
Cheers, Elliot

Posted by: seanery Jul 4 2003, 10:14 PM

I put new brakes on my harley (new stainless lines) and I was amazed at both the quantity of fluid and how damn long it took to bleed the whole system properly. I'd say drive it (as rusty said) and then refill and rebleed.

Posted by: SirAndy Jul 4 2003, 11:39 PM

works best with a second person doing the brake pumping ...

pump 5 times, then hold pedal down, start bleeding until the brake pedal hits the floor.
leave brake pedal down, close bleeder. repeat until no air bubbles anymore.
repeat on all 4 calipers.

pedal should be firm.
if not do the same with the proportioning valve.
still no luck? bleed/replace master cylinder ...

hope that helps a bit,
Andy

Posted by: ! Jul 5 2003, 12:03 AM

Bleed, bleed, have a beer, beat the dog, bleed, have another beer, drive it, bleed, beer....driiivvevevevittt.....bbebebebrbbrrrreer.....

Posted by: Mike's2nd914 Jul 5 2003, 07:26 AM

I willing to follow Mikez's advice about the beer anyway.

Posted by: rhodyguy Jul 5 2003, 07:56 AM

get speed bleeders ( about $30 for 4), and put them in the top bleed valve holes, made bleeding so easy i couldn't believe it. literaly minutes instead of the usual bs. even so i will go to a brake shop and have them use their machine to pull the fluid through instead of me pushing the fluid with the brake pedal. the sequence that you bleed is important too.

kevin

Posted by: Lawrence914-6 Jul 5 2003, 08:31 AM

Speed bleeders are awesome.

I would recommend rebleeding. This time only put the rear of the car up in the air.. then lower it and do the front.

Keeping just one end of the car up, will help coax the bubbles up through the lines to the calipers.

Posted by: Mike Wofford Jul 5 2003, 09:21 AM

Make sure that you have your rear brake pads adj. properly. ( inside and outside adjustment. You will need to use a feeler guage and allen wrenches a tee handle to come thru the rear trailing arm.
Mike

Posted by: Mike's2nd914 Jul 5 2003, 12:12 PM

Thanks Mike. I need to check the adjustment.

Posted by: Anton Jul 6 2003, 05:10 AM

Listen to Elliot.

Suggestions like using ATE blue brake fluid or steel braided brake lines are not very helpful. Do you REALLY believe that a different brake fluid will cure the excessive pedal travel such as you decribe??? Or that standard brake lines will leave you with a spongy pedal??? Don't think so.

Go gor the MC; I had EXACTLY the same problem after revising the rear calipers. The old 16mm MC was swapped for a 19mm 911 type and the problem was solved. On afterwards inspection, the old MC showed some nasty grooves on the inside...

Additionally comes brake system bleeding, adjusting the venting clearance on the rear calipers, and adjusting excessive front wheel bearing play (!). My brake lines were replaced just a few years ago, but in case of doubt, get new ones; it doesn't cost that much.

And you know what? A 914 is able to brake!

Posted by: URY914 Jul 6 2003, 06:21 AM

Anton,
I agree that different fluid won't make the pedal any harder, but I think you're wrong on the brake lines. I've seen stock lines get a fat spot in them and split. Thirty years of compression and expansion of the brake fluid takes it toll on them and they wear out. There is more pressure on a brake line than a fuel line, so stainless steel lines are recommended.

Here is another bleeding tip: Pump the pedal up several times until it is hard and than hold it down for a minute or so. If the pedal slowly goes down, you have a leak or the MC needs to be replaced.

And BTW- don't try rebuilding the MC, just buy a new one, they are such a PITA to get on and off, don't waste anymore time trying to save a few $$$.

Paul

Posted by: Anton Jul 6 2003, 10:01 AM

Thanks, Paul. I forgot to mention the tip of holding the pedal down... Indeed, in my case the pedal slowly sank to the floor.

Frankly, I have never used steel brake lines on any of my cars, but only original items.

Stainless steel braided brake lines are illegal in some areas. The outside obscures the rubber making it impossible to see any defects (cracks or bulbs). That is why they are not allowed for street use in Europe. Subsequently, once you start using these brake lines, a regular replacement (every 3 years or so) is indicated regardless of outside condition.

For the dedicated AX driver this probably is fine, as they offer the advantage you claim, but for guys like me (street use only) this seems not feasible.

Posted by: Mike's2nd914 Jul 6 2003, 12:53 PM

Wow guys, some great suggestions. I jacked up the rear of the car only and bled the rear again. I got a little more air out and now I have a (very) little pedal prior to pumping. I am going to bleed the front in the same fashion (front jacked up only) and see if that helps. I also ordered the speed bleeders. My wife is tired of pumping (insert sexual inuendo here) .

I noiticed the 19mm MC is cheaper than the OEM model. Cool. If the additional bleeding doesn't solve the problem, I'll be ordering the 19mm.

Thanks

Posted by: Porsche Rescue Jul 6 2003, 01:15 PM

Before giving up, be sure to bleed the proportioning valve too.

Posted by: seanery Jul 7 2003, 08:46 AM

the 19mm mc is worth doing it all over again.