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MG MGA - New leaking master cylinder

OK, so I'm either very unlucky or something is telling me not to take the MGA to Gatlinburg. Has anyone else found that a new master cylinder right out of the box starts to leak without ever being on the road? I just installed this thing last weekend, filled with DOT 5 and bled the brakes and clutch. When I started working on the car this morning I checked the MC and found the front side wet with silicone fluid. I'm pretty sure it's the brake side.

I wouldn't be so PO'd if this thing wasn't such a PITA to R and R.

Any ideas other than tossing it into the snow and sending the old one out for a rebuild?

Thanks,
Dave
David Ahrendt

Hi David. It is likely that one of the seals on the affected side is not seated properly. You should be able to remove the piston with removing the entire master cylinder. This situation however, must be extremely frustrating! Where did you purchase the leaky master cylinder from? Cheers! Glenn
Glenn

David,
I'm told by the folks at Apple Rubber, the folks that sleeved my MC, that if you travel the full stroke when bleeding one can uncover a bleed hole that will permit fluid to escape to the wrong side of the piston. I'll look it up and forward this on to you.
Regards,
Doug
D Sjostrom

David, yes indeedy. I put my rebuilt in and it leaked before I ever got to drive the car. Bubbled the paint on the freshly blasted and painted brackets. PMO.

Doug, I had the same info from them. Barney G, in essence, said it was BS, that it could not go far enough to uncover the hole. When I pulled the leaker out and checked it closely I found that Barney was (as usual) correct; there was no way the seal could go past the hole. The new rebuilt just plain leaked. The replacement they sent me has not leaked, knock on wood.

I should caveat it by saying that this what I found on my rebuilt MC for the MGA, I can't speak for other LBCs that may use a similar MC.
Wray Lemke

David, Take it apart and check for shavings, my new one from Moss was full of the stuff. Luck, Neal Turner
Neal Turner

I have had one that leaked from new, sent it back for a replacement which does not leak, still waiting 1 year for refund for the first one (£165)Lockeed are still investigating why it leaked in the first place. Bought it through Midland and Classic.
Dave
Dave

I just a thought! I bled the brakes using an EZBleed and I now recall that when I was done the MC was full right to the brim. I recall thinking at the time that I should probably siphon some of this off. After exercising the brake pedal a few times to check the brake lights I noticed that the level was now down to the bottom of the cap threads.

Is it possible that some of this excess fluid was allowed to escape? I guess I can just pull the front dust cap loose and see how much runs out. I'll try this tonight.

BTW, this is a new Delphi (was Lockheed, I guess) unit made in some unidentified EU country. It came from Moss but they probably have little to do with it.

Dave
David Ahrendt

Hi folks. I am hearing VERY scary stuff in this thread! Leaky brand new master cylinders, lots of metal shavings in brand new master cylinders, etc! Excuse me dear parts suppliers, but our very lives depend on the integrity of our hydraulic systems, and yet, it would appear that quality control on these critical items is less than acceptable! Presumably, customers send defective, leaky hydraulic parts back to their parts suppliers. So my question is, why dont the suppliers who take back the defective parts, raise HELL with the manufacturers on items that are safety critical? Some day, some unfortunate British car owner is going to die or be seriously injured because of faulty hydraulic system parts! Is it going to take a major lawsuit before parts suppliers do something about this most serious problem? Sorry for the rant, but this kind of negligence makes my blood boil! Glenn
Glenn

I have issues with my new master cylinder so I would like to reactivate this old thread. I have just returned from the Le Mans Classic (brilliant trip),had a great time but always in the back of my mind was the leaking master cylinder.
The day before I left, I noticed a pool of brake fluid (silicone) on my newly fitted rubber mats - not obvious on carpet. Master cylinder has done 500 miles only. I decided to re-rubber the cylinders before leaving, luckily I had an NOS lockheed kit in stock. To begin with all seemed fine, but each day of driving lost about 10mm of fluid level, requiring constant monitoring. Apart from feeling a bit dead (brakes not me - thankfully),the brakes work fine, as proved by a 4-wheel lock up when a slow lorry pulled out on us on the A1 leaving me nowhere to go but under his tailgate - pulled up dead straight, what a machine!
Anyway it seems to me that there is a problem with these cylinders - my son has an A Coupe, with a new cylinder, that also leaks but not as bad as mine. Anybody else any input/solutions for this?
I might add that both of the above cylinders were purchased about 3 years ago and fitted during restoration. The "new" rubbers that came out of my m/cyl are marked Lockheed and are very soft, much softer than the NOS ones that I put in.
Do I just buy a new cylinder again and hope for the best? Any recommendations please.
Thanks Tony
Tony Mitchell

Tony, to balance the comments on this thread with regards to good and bad experiences. I replaced my master cylinder with a new ap-Lockheed unit (from MGOC) at the end of April. Running with DOT4 fluid and 1500 miles later the front of the M/C is dry as a bone.
Lindsay Sampford

Where is the leak coming from. The key is to know where the fluid comes out, and this is not always easy to detect. I also had a small leak after rebuilding it.

It turned out it was the output pipe fitting which was not tight enough. It has to be VVFTight otherwise it will leak. This is where a flare wrench is REALLY handy, as the access is difficult.

An I also overfilled it slightly so if you brake aggressively some fluid will come out the breather hole!

If the fluid is coming out the front end of the cylinder then you need to re-inspect the rubber on the piston...maybe bad batch/damaged or slightly too small for the bore, or soft?

I am using DOT3.

my 2cents!
Gonzalo Ramos

I agree with you Glenn - your rant is spot on. I replaced the rubbers on my m/c (original) a couple of years back and this no longer leaks , so the replacement seals are OK. I hope this gets sorted out before I need a new one .
Cam Cunningham

I know exactly where the fluid is coming from - the front endplate of the master cylinder. So fluid is getting past the seals presumably in the relaxed position (as the brakes actually work ok and there is a firm pedal). However it is disconcerting to drive knowing that fluid is being lost. I called at Moss today to pick up yet another master cylinder kit. Carl at Moss did suggest that maybe the problem lies with my use of Silicone fluid. Is this likely, or have I just got rogue new cylinder?
Tony Mitchell

Oh oh! I do hope you get your MC sorted with the new kit as that must be worrying for you, but I fear some sparks may fly over a silicone debate!
Graham M V

Since Barney has done over 100,000 miles with silicone fluid (with no problems) plus countless others, including myself, I very much doubt that is the problem. I'm surprised the folks at Moss even suggested this since they sell silicone fluid.

--Jack
JM Morris

Tony, I have been searching for causes of you leaking problems. Did you start using silicon fluid with an all new system devoid of any DOT3 or DOT4 or anything else, contamination? If not, it may be worth considering the quote below.

"The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some BMW owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. BMW brake systems should be flushed only with DOT 3 or 4.

If silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly."

The quote below may be relevant, but might just be anti-silicon propaganda!

"Sealing

One of the final disadvantages of silicone brake fluid is sealing. Glycol-based fluids are easier to seal because they can't pass through small pores in the system. Silicone brake fluid will pass through smaller pores in seals and gaskets. Therefore, it is much harder to seal effectively."

I have no axe to grind one way or the other, my hydraulic system has DOT4 fluid in it because I am not prepared to strip the whole system, clean it out and replace all the seals in order to use silicon brake fluid.

Lindsay Sampford

Concerning the silicone issue, Carl's suggestion was just that - a suggestion that in this instance maybe silicone fluid is not helping. Indeed it is well known that silicone fluids' properties seem to allow it to "reach parts that Dot 4 fluids don't". to quote a well known ad. In the past I have had great results - running silicone in a TC for 15 years without problem.
So far as the brake system is concerned, it is all new - pipes, caliper pistons and seals, rear cylinders.
If anyone else is thinking that they may have the same problem, the first clue - that I did not really pick up - was a misting of fluid on the bulkhead around the m/cyl area. My sons A shows the above symptom, but not the full blown runs down the pedal - yet.
I guess what I am trying to establish is the same as Glenn, how widespread is the problem? ........ Going into the garage to examine the old seals with a magnifying glass.....
Tony
Tony Mitchell

I have had a lot of MC trouble, including leaks, over the recent years but thankfully now solved.

I bought a new unit from Bob West. It is made by AP Caparo who bought out Lockheed's tooling. Bob says that AP Caparo's machining is to a much higher standard than Lockheed's ever was and has cured any number of problems from leaks to slow release brakes. On the downside, it costs about half as much again than other units. Nevertheless, probably worth the investment in this better quality item than the cheapo units regularly advertised on Ebay etc. Delighted with my 'dry' MC to date.

Steve
Steve Gyles

Hi Steve,
Thanks for the input. Unfortunately the box that my cylinder came in is long gone and I cannot remember what was said on it, I do however remember buying it from the Welsh MG Centre stall at MG Silverstone 2007. However the cup seals that I have removed from the new cylinder are marked Lockheed and are numbered exactly the same as my NOS original replacements, if that tells you anthing. I do know that new replacements from Moss simply state "Made in England" with no manufacturer reference.
Interestingly when viewing the used seals with a magnifying glass, the edges of the secondary seals are both "raggy", ie not a clean edge to the lip. Both cups seem to have quite a good edge. As a result of this I think that I need to investigate further the "manufacturing swarf and debris" theme.
I have to admit that when changing the seals prior to the Le Mans trip, I was in a hurry and paid more attention to replacing defective seals than cleaning out cr*p in a brand new cylinder.
Cheers to all, stil dripping, hopefully included is a picture of the offending seal edge.
Tony
Tony Mitchell

I have just rebuilt my MC (original Lockheed) and plan on using DOT 5 silicone for the first time. One problem I had was getting the brake-side washer out. Finally left it in and replaced the rest. Any thoughts on whether this may turn out to be a problem. (Still working on the brakes and clutch slave so haven't road tested it yet).
thanks in advance - I am a newbie to this site and think this is a great venue for enthusiasts. Hope I can provide constructive comments one day
G W White

GW

I make no claims about being a brake expert, as I have had more than my fair share of leaks and MC problems in recent times. My only concern with that stuck washer is that it has spent its life submerged in mineral fluid and now it is going to be smothered in silicone - not an ideal mix.

The recommendations of most posters on this site is that, when changed from one fluid type to another, is to change all the rubber seals, including in the wheel brake cylinders, and flush through the pipes.

Steve
Steve Gyles

I will only say this. When restoring my A some 12-15 years ago and with new wheel cylinders and a re-sleeved master cyl, I used silicone fluid. After failing to staunch the leaking, I switched back to glycol based fluid and no problems since and a good firm pedal.
That's my story and I'm sticking to it!
BRIAN WARMUTH

thanks for the advice Steve, I haven't got my calipers back from rebuilding yet so I have time to go into the MC again. Any tips on how to get that washer out without scoring the inside?
Gerald
G W White

Gerald

Assuming you are replacing the washer I took a flat head screw driver which was slightly larger than the hole in the middle of the washer and forced it in; then rotated the screwdriver while gradually pulling on the washer.

Steve
Steve Gyles

Steve, thanks and I will try that. Will be in UK in two weeks but up north (Peak District) otherwise I would try to visit.
Best..... Gerald
G W White

This thread was discussed between 12/02/2006 and 01/08/2010

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