Brake fluid disappears?

[Steve-B]

Hi, I am a bit confused and hoping the collective wisdom can help. 1973 Pi CR  

Been out a few times in the last week and before todays drive, I checked the brake fluid as they were a bit squishy the other day. 

I opened the brake fluid reservoir and found it quite low as when I previously checked it ~4weeks ago it was full.  I ended up putting about 6 ounces in to fill both reservoirs.

Spent the afternoon out and about all was normal brakes wise. Checked under car, on floor and under brake servo and it’s all dry!

What should I be looking for/at?

 

Edited August 11, 2023 by Steve-B

[Tom B]

The brake fluid may have drained into the servo unit. To check, the servo should be removed. You will probably find the fluid in there. The master cylinder will require attention.

[Steve-B]

Thanks @Tom Bfor the pointers. If the servo contains fluid does it mean it needs to be replaced as well as servicing the master cylinder? Or if it contains fluid, just rebuilding the MC?

[Kiwifrog]

Check the brake light switch, they can leak

[FatJon]

2 hours ago, Steve-B said:

Thanks @Tom Bfor the pointers. If the servo contains fluid does it mean it needs to be replaced as well as servicing the master cylinder? Or if it contains fluid, just rebuilding the MC?

The servo will be fine, drain it and put it back in use.

[Steve-B]

1 hour ago, FatJon said:

The servo will be fine, drain it and put it back in use.

Thanks Jon, I’ll do just that. Gotta source parts for rebuilding on Monday. 

[Waldi]

Agree with John: if you do not find fluid anywhere (and 6 ounces is not a bit, so cannot be missed), it is most likely in the servo, because the MC is leaking. 

Waldi

[Steve-B]

Hi guys,

I'm getting ready to attack the underlying issue and wanted to sanity check what I will need before starting. I've searched the forum for links to a how-to but as of yet haven't found a good guide. I feel OK in doing this, as I've done it for years on cars without a servo, however I'm unsure with the servo how to disassemble.

1. I presume I'll need a Master Cylinder reseal kit with all the gubbins - I checked at TR Shop and they have one so I'll get that
2. Presuming the servo is full of brake fluid, I will need to capture and safely dispose of that - is the local council tip best for that?
3. I'm guessing I'll need to bleed the brakes when I've rebuilt the MC -- is the Eezibleed the best way to do so?
4. Will 1 litre of DoT 4 be enough to refill?

Thanks in advance for your counsel!

[Mk2 Chopper]

1 hour ago, Steve-B said:

Hi guys,

I'm getting ready to attack the underlying issue and wanted to sanity check what I will need before starting. I've searched the forum for links to a how-to but as of yet haven't found a good guide. I feel OK in doing this, as I've done it for years on cars without a servo, however I'm unsure with the servo how to disassemble.

1. I presume I'll need a Master Cylinder reseal kit with all the gubbins - I checked at TR Shop and they have one so I'll get that
2. Presuming the servo is full of brake fluid, I will need to capture and safely dispose of that - is the local council tip best for that?
3. I'm guessing I'll need to bleed the brakes when I've rebuilt the MC -- is the Eezibleed the best way to do so?
4. Will 1 litre of DoT 4 be enough to refill?

Thanks in advance for your counsel!

Hi Steve, 

You could try a rebuild kit for your MC, but if there is corrosion/ scoring then it might be a temporary repair. I think you can have original MC's rebuilt. 

Council tip take oil, not sure about brake fluid, maybe a jar into the black bag would have to do? 

Yes you'll need to bleed the brakes, I'm old school and still like to do it with another person operating the brake pedal. 

I litre should be enough to do it. 

Gareth

[Steve-B]

45 minutes ago, Mk2 Chopper said:

Hi Steve, 

 I think you can have original MC's rebuilt.

Gareth

@Mk2 Chopper do you know any firms that I can send ours to for a rebuild? Must admit it doesn't look impossible, but I'm sure many have said similar things before!

[Iruka]

Hi, just had my M/C resleeved by these guys. Good service and easy to deal with.

Steve

 

[Mk2 Chopper]

1 hour ago, Steve-B said:

@Mk2 Chopper do you know any firms that I can send ours to for a rebuild? Must admit it doesn't look impossible, but I'm sure many have said similar things before!

Looks like I was beat to the answer, that's the place to use. 

Gareth

[Steve-B]

Brilliant guys, thanks very much! 

[mhossack]

Hi Steve-B

Good to hear you are going to get your original parts rebuilt, my 1975 TR6 before I purchased it had rubbish aftermarket parts which did not last 2 years, I sourced original parts and used pastparts very pleased.

I don’t think you are going as far as I did, I renewed the lot and used silicone brake fluid, that really starts a red hot debate.

Michael.

[Steve-B]

@mhossack FYI -  I’m thinking if I’ve got the MC out & being reconditioned I might as well the servo whilst I’m at it. Really don’t want to buy cheap Chinese tat.
 

PS> I really hate taking apart one thing to fix and not take advantage of the other being readily accessible later = facepalm!

[PodOne]

6 hours ago, Steve-B said:

 

1. I presume I'll need a Master Cylinder reseal kit with all the gubbins - I checked at TR Shop and they have one so I'll get that
2. Presuming the servo is full of brake fluid, I will need to capture and safely dispose of that - is the local council tip best for that?
3. I'm guessing I'll need to bleed the brakes when I've rebuilt the MC -- is the Eezibleed the best way to do so?
4. Will 1 litre of DoT 4 be enough to refill?

Hi Steve 

Commissioned my brakes a short while ago. Just my experience after asking other formites and it worked well for me.

1. Recommission your old one via Past Parts as suggested above its your best option after 50 years its likely to need some TLC and it will be a safer bet.

2. Loads of rags black bag and bin

3. Eezibleed Pressure kit. Get hold of a new/old MC lid and adapt it. Run it at 5-8psi from the spare tyre. The two person method left me with a poor pedal after numerous attempts. The Elizibleed  kit (£24) made the difference - rock hard without the servo assistance. Same with the clutch hydraulics.

4. 2l just I case and you can completely flush the system its cheap enough any left over you can give the clutch a refresh.

While you are there is a good time to check for leaking cylinders and the rubber lines for cracking/bulging and replace with SS lines (Goodrige) 

Andy

[Tom B]

Steve, If you are removing/replacing the servo or the master cylinder you should check the clearance between the push rod and the master cylinder. There was a thread on the forum about this. It can be a frustrating "gotcha" if you are not aware of the issue.

Tom

[mhossack]

Hi PodOne

I also purchased the Elizibleed kit, easy to use if you have a spare M/C cap which I did.

I found I had to watch I was not loosing pressure between each wheel bleed so topped up the air after each wheel but apart from that quite easy.

People on here who are more clever than me, I may be wrong, if you don't have a spare M/C cap you could always cap the hole with a small nut bolt washer, and fibre washer after bleeding the system only a thought.

Michael.

[Steve-B]

6 hours ago, mhossack said:

Hi PodOne

I also purchased the Elizibleed kit, easy to use if you have a spare M/C cap which I did.

I found I had to watch I was not loosing pressure between each wheel bleed so topped up the air after each wheel but apart from that quite easy.

People on here who are more clever than me, I may be wrong, if you don't have a spare M/C cap you could always cap the hole with a small nut bolt washer, and fibre washer after bleeding the system only a thought.

Michael.

Michael, am I looking at the right kit here?: https://www.halfords.com/tools/hand-tools/automotive-tools/gunson-eezibleed-321158.html

[Steve-B]

15 hours ago, Tom B said:

Steve, If you are removing/replacing the servo or the master cylinder you should check the clearance between the push rod and the master cylinder. There was a thread on the forum about this. It can be a frustrating "gotcha" if you are not aware of the issue.

Tom

Thanks Tom, I'm thinking of just removing it and sending it for reconditioning to Past Parts when I send them the MC. Just gotta figure out how to remove the servo first...

[mhossack]

Hi Steve-B

Yes thats the one Gunson Eezibleed, I purchased mine from Halfords.

Michael.