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MG MGA - Ever Seen This?

Brake fluid (silicone)leakage from the cylinder bores due to extreem cold?

This is a newly (stainless steel) sleeved MC with all new rubber. I chased down leaks on this all new system throughout last summer. Most were from fittings under tightened. I completed the chassis restoration to drivability just so there'd be a period of easy access to "debug". At most there are 10 miles on the bare chassis. Could the MC rubber just need to wear in?

Thanks,
Doug
D Sjostrom

Hi Doug. I have never heard of Master sylinder seals having to wear in, and I dont think that the leakage you describe is normal. Here in Ontario Canada it sometimes reaches minus 50 degrees F! That is colder than a bosses heart! But I have never noticed any leakage from my master cylinder, even in extreme cold, when my car has been in accessible storage. If you are certain the leakage is from the cylinder bores, then some possibilities to explain your leakage might be: Dirt or grit in the master cylinder, damaged or scored cylinder bores, poor quality/defective rubber seals, extreme cold makes defective/ marginal seals hard, thus allowing seepage. Perhaps other folks have other thoughts or info on your problem. I look forward to you finding out what the problem is. Cheers! GLenn
Glenn

Doug, where did the MC come from?
Wray Lemke

Apple
D Sjostrom

Doug - I don't know about Apple, but White Post recommends against using silicone fluid in sleaved cylinders. Their reason for this recommendation is that silicone fluid, like synthetic oil will leak past the tinyest hole and they have had problems of it leaking past the sleave to cylinder wall interface. While I have never talked to anyone who has experienced this situation, there is always a first time. It is going to be very difficult to prove that the leak is past this interface, but if you can, Apple may redo the work for you. Good luck - Dave
David DuBois

Dave,
I suspect you're right. I sleeved my clutch slave with brass and went to great lenghts to insure the loctite anaerobic adhesive was thoroughly distributed. Unfortunately, it was a few years ago that I had the MC done and they'll probably resist a request to make good on the job. When I have to pull it to re mount the body, I'll give it a good exam. opefully it's just a matter of improving the bore finish which is sonething I can do myself.
Thanks,
Doug
D Sjostrom

Doug,

I think Dave DuBois has hit the nail on the head. Silicone brake fluid is a definite no-no. Here in Québec, where we can get the -50° stuff too, (and that's colder than a Nun's nipple!); I have usually stored my car in my unheated garage and I've never experienced leakage in my braking system.

Each spring I do the regular maintenance of my system and so far so good. But I was cautioned about silicone many years ago, and so far, that has proven to be good advice.

Gord Clark
Rockburn, Qué.

Gordon A. Clark

This is the usual argument about Si fluid. If a brake system is not perfect, it will leak, whatever goes in it. If it leaks, it is defective and needs immediate repair - saving money here is just ridiculous.

I have used Si fluid for almost 20 years, have never had a leak, and never have problems with my brakes. Ever.

After 15 years I still replaced all the rubber seals and hoses, even though they still looked perfect. It just is not worth finding out the hard way that you brakes are sub-par.
dominic clancy

I agree with Dominic regarding leaks, but silicone fluid will leak where standard DOT 3 or 4 will not. I had one wheel cylinder connection on our TD that I had to redo several times and finally had to lap both surfaces before it would seal up, whereas it never leaked with the old DOT 3 or 4 fluid inthe system. Onec I got that fitting sealed, I have never had a leak in over 20 years and am a great fan of silicone fluid. Like Dominic, I have never had a problem with the brakes in the TD in over 20 years or the MGB in over 10 years after having converting them both to silicone fluid. Cheers - Dave
David DuBois

Doug
Your use of Apple to rebuild the cyl is probably the answer! I wouldn't use them again in a million years - although my problem was the rebuilt shocks.

Rick
Rick Brown

I bought a brand new master cylinder, had it on the car for 2 years while doing the restoration, filled it with Silicon fluid near the end of the restoration and it leaked at the seals. Exchanged it for another one, this one does not leak.
Dave

I have a brass resleeved unit from Apple. While it works just fine, they tell you not to use silicone fluid as it will leak around the sleeves. I thought that use with stainless sleeves was okay. With your MC you should also have received a fact sheet that had a few do's and dont's and it would have told you whether silicone fluid was a no-no in your resleeved unit.

Did Apple send you a completely finishied unit or did you assemble the resleeved unit yourself? If they built it for you, they'll take it back no questions and fix it for you. If you put it together, I would take it apart again and inspect the seals, make sure nothing's damaged, put together wrong, etc. One you have determined that it's leaking from around the sleeves and not from the seals Apple should send you a new one.

I have heard a few pro's and con's regarding Apple Hydraulics, but I will attest to their customer service. I thought I was having a problem with my resleeved unit (turned out to be bad seals) and over the phone they were very accomodating. Even though I had assembled it myself, they told me to ship the unit assembled and whatever the problem was they'd send it back working properly.

Good luck.
Mark
Mark

I run a repair shop in Denver on days below zero the incidence of brake fluid leakage goes up in any car. Seals don't seal as well cold.
Silicon fluid does leak earlier than the other fluids. Constant use keeps the leaks down. Sitting for an extended period makes leaks more likely.
That said I will only use silicon fluid. The regular fluid eats the paint on the shelf under the master cylinder. That is worse and more work than being careful with the work you do chasing and fixing leaks.
Any company that recommends against silicon fluid because of leaks is admitting to poor quality control and blaming the customer for sloppy work.
One of the reasons that brake components last longer with silicon fluid is that it doesn't attack the rubber like regular fluid does. This is a two edged sword. Because it doesn't attack the rubber and soften it silicon needs everything to be in better condition for it to not leak.
If silicon leaks you wipe it up When regular fluid leaks you repaint the engine compartment.
This is one of those situations where opinions run strongly both ways. Silicon is harder to work with but in my opinion well worth it.
R J Brown

Barney has definitive opinions on Apple's rebuilds. I had to replace a new rebuilt from them when it leaked a couple of days after I'd installed it and bled the system. The pita was that the fluid ate my fresh paint job on the shelf and brackets. Arrrggghhh.

They sent a replacement out right away with a call tag for the defective one. That's good. But, I shouldn't have had to replace the new one.

Next time the core will go to Joe Curto. I can wait on him. I ended up not saving any time by getting one off the shelf from Apple.
Wray

Thanks All,
Apple was very helpful in suggesting some possible causes among which is when bleeding, it's possible to uncover a bypass port at the very end of the downstroke which may allow fluid to escape on the wrong side of the piston. I've cleaned up everything well and will more closely monitor for additional dripping. If the leakage persists, I'll block the pedals to allow backing the front plate away from the bores. Hopefully this will allow me to determine whether the leak is from the piston seals or the sleeve-to-bore adhesive joint. They've offered to make good on their work should it prove defficient.
Doug
D Sjostrom

This thread was discussed between 07/01/2006 and 10/01/2006

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