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Brake Fluid Splashing Under the Bonnet

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SHG

SHG

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I started seeing the paint deteriorating under the bonnet just forward of the carbs. It finally dawned on me that it was the brake fluid splashing up from the resevoir. The brake fluid around the rim was the giveaway.

Does anyone know why this is happening and what to do about it? I tried tightening the two screws that hold the bracket to the frame (one was very loose and the other was slightly loose) but the bolts are frozen and I can't get anything behind them to break them free because the cold air hose is in the way. Still, I don't think this is the problem and have no idea why brake fluid is escaping from the reservoir and splashing around. It made the inside of my hood a real mess. Yoda? Please tell me what to do (and in English, please).
 
A couple of possibilities: 1. Brake fluid might be coming out of the vent hole in the lid of the reservoir. I have replaced the rubber washer that fits inside the lid with one that has a very small hole istead of the larger opening. I believe others on the forum have replaced the washer with a solid one, but check the search feature to be sure. The second possibility and one I just experienced was a very small leak at the bottom of the reservoir where the brake and clutch pipes connect leading to the master cylinders. While the leak was very small, ( I hardly noticed a drop in the fluid level inside the reservoir), the engine fan blew the few drops all over the drivers side of the engine compartment, creating a mess. I had to tighten the nuts inside at the bottom of the reservoir. The inside cylinder for the clutch needs to be removed to tigthen the nut for the brake line. Before doing that though, check and see if there is any fluid on the brake/clutch lines where they leave the reservoir. That should give you a clue.
 
"Stat-O-Seal" or "Dowty" washers work well for sealing th bottom can fittings.
https://www.mpsracing.com/products/Earls/PA_Seals.asp

The "Help #42072 Master Cylinder Gasket" from local auto parts stores, seals the top cap perfectly. You do need to seal the tiny slit in the rubber with JB Weld. This gasket has the added advantage of preventing any air moisture entry into the brake fluid, while still letting fluid easily transfer to & from the MC.
D
 
HI SHG, First That rubber seal Identified by "Greg" that fits inside the reservior cap is available from Pep Boys and others. This seal will stop the fluid from coming out the top of the reservoir. Additionally the reservoir is setting too high in the bracket it must be carefully loosened and moved down a bit. It is a bit of a chore to get a 1/4" socket on to those nuts but it can be done. Alternatively, soaking with PB Blaster and patience may allow them to be loosened.--Fwiw---Keoke
 
I checked the top gasket and found that it had been replaced by the PO. In fact, there were 2 gaskets put together. I assume that the replacements weren't as thick as the original gasket, and that was their solution. Can anyone tell me what size gasket should be in there? I'll run off to Pep Boys and ask Manny if he's got one. Thanks.
 
[ QUOTE ]
I checked the top gasket and found that it had been replaced by the PO. In fact, there were 2 gaskets put together. I assume that the replacements weren't as thick as the original gasket, and that was their solution. Can anyone tell me what size gasket should be in there? I'll run off to Pep Boys and ask Manny if he's got one. Thanks.

[/ QUOTE ]


Hi TH, That is not the type[Gasket] seal for the reservoir I am are refering to. Do a search on the forum and find the part number of the item we are using.Keoke--- /ubbthreads/images/graemlins/hammer.gif
 
--- /ubbthreads/images/graemlins/savewave.gifTH!

That #42072 is the correct seal I missed that one


somehow seal the little slit with Super Glue.---Keoke
 
Hi Scott,
Right in the middle of the gasket, there is a small slit maybe 3/8” long. You have to bend the gasket to see it. My opinion is the slit doesn’t need to be glued. When I bled my brakes with the top screwed loosely to the reservoir, the vacuum created by the fluid leaving the reservoir pulled the gasket out of shape. I had to push the bellows (of the gasket ) back in at least twice. As a test, I put brake fluid in the cup of the gasket overnight on the bench. Next morning, nothing had wept through. Not very scientific, I know. /ubbthreads/images/graemlins/grin.gif
 
[ QUOTE ]
what little slit? It looks solid in the photo.

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Oh! them looks is deceiving TH. I missed it the first time out too.Dave had to tell me how to see it.So now you found it too-Huh--Keoke-- /ubbthreads/images/graemlins/lol.gif
 
I did not glue the slit either. To be honest, I didn't even see one. I will say, that the rubber fit is tight along the edges, and needed a little help with pushing the edges down flat. A little muscle was needed to screw the cap tightly down. Once on, problem free. Every once in a while, a simple quick fix. How about that. Roger
 
/ubbthreads/images/graemlins/savewave.gif Roger, I had to trim the outside diameter down just a bit to get a good flat fit. However, I do not use the Aluminum top on a tin can /ubbthreads/images/graemlins/nonod.gif. Mine is plastic from a volvo reservoir.---Fwiw-Keoke- /ubbthreads/images/graemlins/yesnod.gif
 
My two cents.... The slit is made to relieve vacuum when the fluid gets real low. If it didn't have this slit in it, it would probably tear along the bellows. Under normal conditions inside of the systems, the slit should not allow anything to penertrate into the fluid. If the fluid gets low enough to allow air/moisture to enter, then you will be shortly filling it back up with new fluid ,( right after you find and fix the cause of the low fluid )!
... I remembered to buy one of the "Help #42072 Master Cylinder Gasket" yesterday and noticed the slit that you all were talking about as I was installing it.
 
picked on up today. Everything makes sense now. The zen of Healey. Thanks guys.
 
Update. So I changed the gasket without incident. I've driven around a while and...the problem persists.

The leak is definitely on top, as the fluid is around the rim of the reservoir. It's not coming out the vent hole, which is dry. I don't see any cracks in the top of the reservoir. But there is quite a bit of fluid there. Any ideas?
 
SHG, Take the gasket out!. Take your finger and push up on the center section of the gasket. You should now see a very small slit.Using super glue close it up!.Be sure you have U specks on so you don't miss seeing it.---Keoke-- /ubbthreads/images/graemlins/laugh.gif
 
I noticed the same thing. Fluid escapes through the slit in the top of the rubber, but instead of going out the top vent hole, runs down between the inside of the metal cap & the outside of the rubber & comes out around the cap rim. Thus, the need to block the slit. Don't block the vent hole in the metal cap.

Blocking the slit does NOT cause a vacuum to form in the can because the bellows type rubber gasket easily collapses downward as needed to follow any fluid level drop. It won't tear. The rubber forms a flexible sealed diaphram just as in modern cars which do not have a slit.

When replacing the cap, make sure that the diaphram is fully pushed up into the cap to give it room to move down as needed.

Possibly, if you only fill the can about 3/4 full, it wouldn't slosh out the top slit but no guarantee. Most of the cars get some pretty violent sloshing during stopping & turning maneuvers.
D
 
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