S2 - Losing Brake Fluid - Update

(Geo Hahn 1969 Series 2 OTS) #1

On my Series 2 I seem to be using brake fluid from the rear reservoir. On the Oil Leak this worked out to a consumption of about an ounce per 500 miles.

No evidence of leaks and the vacuum tank has no fluid in it so I suspect it is finding its way into the engine and then out the tailpipes.

My question - what is the likely failure & remedy?

Is it simply a matter of rebuilding the remote servo or is the booster itself to blame?

This is my first car with a brake booster so I have no experience with what can go wrong. Thanks for any advice.

(L.Lynn '68 OTS, '73 2+2) #2

Hi Geo,
Sorry to hear that your having issues, I recently was having leakage from the servo reservoir thinking that I had a bad servo master only to find that it was leaking from a crack in the reservoir, since that is an easy fix I’d check that first. After that I suspect that your going to have to look at your servo master cylinder as it could be leaking into the servo vacuum booster tank, they can hold a lot of brake fluid before it starts getting sucked into the engine.

(David Norton) #3

My booster had almost a half gallon in it, between a PO and myself we had managed to top it up for a long time without realizing where it was going. Alas, you will have to pull the booster as the servo is attached inside it.

(Geo Hahn 1969 Series 2 OTS) #4

Okay - that’s sounds like my next task.

Is there typically a solution short of replacing everything? e.g. a rebuild kit for the servo or a seal between the servo and the booster?

(David Norton) #5

The leak is the shaft seal on the booster. I pulled mine apart and the metal parts were in great shape (so was the diaphragm in the booster, sort of surprised me with all the fluid), so I did a light hone on the cylinder and installed a seal kit. Others have needed to replace the parts. Anyway, if you have the time I’d pull it apart, see what you need, then decide what to do.

(L.Lynn '68 OTS, '73 2+2) #6

Morning Geo,
SNG (as do others) sells a kit to rebuild the servo master cylinder, another consideration would be to send it to one of the rebuilders and get it re-sleved. I have used Apple Hydraulics in the past with good results.
There isn’t a specific seal between the servo master cylinder and the booster tank, just the ‘inline’ seal in the servo master cylinder.

(Robert and Darlene Stevenson) #7

And make sure that the pushrod to the servo is 100% smooth.

(Andy.Preston) #8

George, you may have already checked this but I had a small brake fluid leak from the plastic joint on the bottom of the reservoir tank. I only noticed it after I installed the splash shield prior to that it just dripped onto the ground.

Andy S2 FHC

(Geo Hahn 1969 Series 2 OTS) #9

Thanks - I think I have eliminated the reservoir and low pressure hose & connection as the source of the loss.

I have a car show on Saturday (good motivation to clean and detail after the Oil Leak) then I can park the car and remove the servo & slave. Shouldn’t take long to determine if the missing fluid is inside the booster.

If the fault lies there, the entire replacement unit for $260 new (Lockheed) is tempting vs rebuilding what I have with the usual kit.

(Andy.Preston) #10

George if the new Lockheed unit is only $260 I’d buy it providing that is the problem. I never skimp on brakes!

Good luck at the show.


(Skene Black) #11

I had the same problem. Started losing BF in the rear resevoir. My guess per some research here was BF leaking into the booster since there was nothing on the ground or at the calipers. I thought about rebuilding mine, but tried this with my clutch MC only to discover the bore was pitted resulting in a bad seal (not holding pressure) so I replaced it with a new one. Given that I decided to just swap the MC and Servo (purchased the combo from Welsh), knowing mine were about 25yrs old. I got lucky and purchased mine before a ~30% price increase. I still have my old units I will probably pull apart when I have some spare time. Replacing the parts is relatively easy, bleeding the brakes is the “fun” part, especially the rears if you do not have the remote bleeders. I have posted what worked for me as well as many others. You will have no issues with all the resources here.

(Geo Hahn 1969 Series 2 OTS) #12

With the Saturday car show over (lots of fun, too much sun) I now have had a chance to pull out the slave/servo/booster. As expected, I was able to dump quite a bit of brake fluid out of it:

It would seem that it has been going on for some time as that looks like Castrol Crimson which predates my ownership. The clear stuff is my DOT5 (which loses its purple color when exposed to DOT3/4).

Thanks for the advice & correct diagnosis.

(69 FHC ) #13

Ah, so you weren’t losing the fluid, you were just storing it in an alternate location. :smile:

(David Norton) #14

Make sure you check the vacuum tank also, mine had quite a bit of fluid in it too.

(Geo Hahn 1969 Series 2 OTS) #15

Vacuum tank is dry & empty – the fluid in booster made a nice puddle but not the large amount some find. Guess I got it in time.

(Geo Hahn 1969 Series 2 OTS) #16

Yikes - once decanted it was more than I initially thought (that’s a quart milk bottle):

The dark stuff is from the PO, the light what I added in the past 6 years / 30000 miles.

Looking at it makes me thirsty.

(Bob Faster) #17

been there… ( and I am happy to see someone else using the trash can workbench )

(69 FHC ) #18

Mine exhibits several different colors of spray paint.

(Walter Swistak) #19

I have been interested in this thread since I have been mysteriously loosing BF as well. So what I gathered is if the tank is storing fluid the best fix is to replace the booster. Correct? Is that a difficult job. I’m impressed that you could consider doing this while at a show!

(Geo Hahn 1969 Series 2 OTS) #20

I chose to replace the entire with a new unit rather than rebuild the old. No more difficult than any typical brake work – a little messy and somewhat fiddly getting the lines threaded in.

Thank goodness I use DOT5 as there was more than a little dripping going on. Have not yet done the bleeding (have scheduled the wife for tomorrow morning). Pressure bleed has been what worked best for me, I may try the trick with the bicycle tube this time.