Brake / Vacuum Light (1 Viewer)

[WideAngleWandering]

Everytime I press the clutch pedal, the brake light comes on. As far as I can tell, the light comes on under 3 conditions:

1) low vacuum (there is a sensor on the reservoir)
2) hand brake set
3) low brake fluid

Are there any others?

I think that it my case it is a vacuum problem as I can feel the brakes stiffen when the light comes on.

A while back I rebuilt the vacuum pump while doing some work on the alternator. I am certain I put the vanes back in correctly and I'm pretty confident I got the o-ring seals in place correctly ... but it's possible that the pump itself is leaking.

I've changed all the vacuum lines and replaced the finger clamps with real screw-type clamps.

Fluid levels are all good.

Right now my thinking is:
1) leaking pump (probably from one of the o-rings)
2) leaking reservoir (seems unlikely but possible)
3) over-consumption of vacuum or a leak in the clutch cylinder

Right now I'm mostly ignoring it because I'm not losing any fluid and it's more of an annoyance than anything. Suggestions?

 

[WideAngleWandering]

I'm pretty sure it's not a supply side problem, so I'm discounting the pump/reservoir.

I understand the brakes use far more vacuum than the clutch does, and I never have low vacuum from using the brakes alone. This seems to suggest it is a problem in the clutch booster or related plumbing. There is no audible hissing. The low-vacuum light (sensor attached to the reservoir) comes on whenever I hit the clutch but the clutch won't get stiff unless I'm using it repeatedly in heavy traffic. I can feel the brakes stiffen as well but only if I've been working the clutch first.

From browsing the forums, it seems that rebuild kits are pricey and hard to find. Some people have done conversions to non-vacuum assisted clutches but details are scarce.

Advice?

 

[lostmarbles]

Your line of thought and checking process are in line with what mine would be..
So there's not much I can say really.

I'd expect a booster fault ... but then I'd also expect you to be able to hear an associated air hiss...

Do you think the oil flow to your vaccum pump (for sealing, cooling and lubrication purposes) could be hindered somehow?

 

[sved]

Check if you still have vacuum when your engine has been switched off.There should be,even after several days,vacuum left in the tank.

 

[WideAngleWandering]

I borrowed a vacuum gauge and a hand vacuum pump to do some more tests.

The system does hold vacuum after I've shut the engine off ... until you press the clutch predal. Then all vacuum is lost.

The gauge shows about 22" of vacuum at idle with the engine running ... until you press the clutch pedal. Then all vacuum is lost.

I put a hand vacuum pump directly to the clutch booster and it held vacuum ... until I pressed the clutch pedal.

So it seems that the problem is internal to the booster. I'm guessing the diaphragm is probably torn?

I would ignore this problem as it barely affects drivability (and only in heavy stop & go traffic) but I'm thinking about selling it, so I'd like to fix it first. I talked to some folks here in California and nobody has a clue where to find the parts to rebuild it.

Options:

• Find a rebuild kit (there are gaskets and such to be replaced if I remove and open it, in addition to whatever is leaking)
• Find a used, good booster
• Convert to a non-boosted setup

Any suggestions or recommendations?

 

[lostmarbles]

I borrowed a vacuum gauge and a hand vacuum pump to do some more tests.

The system does hold vacuum after I've shut the engine off ... until you press the clutch predal. Then all vacuum is lost.

The gauge shows about 22" of vacuum at idle with the engine running ... until you press the clutch pedal. Then all vacuum is lost.

I put a hand vacuum pump directly to the clutch booster and it held vacuum ... until I pressed the clutch pedal.

So it seems that the problem is internal to the booster. I'm guessing the diaphragm is probably torn?

I would ignore this problem as it barely affects drivability (and only in heavy stop & go traffic) but I'm thinking about selling it, so I'd like to fix it first. I talked to some folks here in California and nobody has a clue where to find the parts to rebuild it.

Options:

• Find a rebuild kit (there are gaskets and such to be replaced if I remove and open it, in addition to whatever is leaking)
• Find a used, good booster
• Convert to a non-boosted setup

Any suggestions or recommendations?

With that degree of vacuum loss I'd expect to be able to hear a hiss to show where the air is entering.

And I have a feeling that a torn diaphragm may cause continual vacuum loss, rather than simply losing vacuum only when you place your foot on the clutch pedal. So perhaps the problem is more easily fixed?

So for a start I'd try to source the leak more thoroughly..

But if you find it is indeed something major like the diaphragm, then I think I'd convert to running without a booster. (The rest of us can manage to disengage our clutches without assistance so why not you? )

 

[HJ61 12HT]

Just pull the vacuum pipe off the clutch booster and plug it.
It will confirm that the fault is in the booster, and give you a feel of how a non boosted clutch feels.
I like the clutch vacuum boosted, so if mine died I would replace it with a second hand one.

 

[HJ61 12HT]

(The rest of us can manage to disengage our clutches without assistance so why not you? )

I wonder if there is some leverage ratio difference somewhere on the boosted clutches, without mine boosted its very very hard to press the clutch in, possible for me but not my girlfriend.
I can't imagine driving in stop start traffic without the boost working...
Boosted it is very light, lighter than your average Japanese car clutch.

Cheers

 

[Tapage]

If you happen to reach Panamá with the same issue I have my Tencha brake booster in one of my shop shelf ..

 

[WideAngleWandering]

So for a start I'd try to source the leak more thoroughly..

There's a valve in there as well that could be leaking, but if I disassemble it I believe I'll have some non-reusable gaskets to deal with, and then I'm back to looking for a rebuild kit that would include those gaskets.

then I think I'd convert to running without a booster. (The rest of us can manage to disengage our clutches without assistance so why not you? )

I'd be fine with that, just not finding much info on how to do the conversion.

I've isolated the leak to the booster but I haven't intentionally driven around with it disconnected. I'll see how that feels.

 

[lostmarbles]

There's a valve in there as well that could be leaking, but if I disassemble it I believe I'll have some non-reusable gaskets to deal with, and then I'm back to looking for a rebuild kit that would include those gaskets.


I'd be fine with that, just not finding much info on how to do the conversion.

I've isolated the leak to the booster but I haven't intentionally driven around with it disconnected. I'll see how that feels.

Following on from the post by HJ61 12HT, you may find you need to swap to different cylinders (probably both master and slave) to obtain more reasonable pedal pressures when unboosted.



PS. Either a larger-bore slave or a smaller-bore master will both decrease pedal pressure I believe. However, each of these moves would increase the pedal travel necessary for proper disengagement. So perhaps it may be best, if you want to go down the non-boosted route and avoid trial-and-error, to study and copy a non-boosted OEM setup actually used on your engine?

 

[WideAngleWandering]

What vehicles would make good donors? I'm not sure which regions/models came unboosted. Mine's a Central American 12-volt 2H (1984).

 

[Tapage]

no 40 / 60 / 70 / 80 series I ever seen with no brake booster ..

the bigger the bore in the MC the harder the pedal smallest pedal travel ..

 

[lostmarbles]

What vehicles would make good donors? I'm not sure which regions/models came unboosted. Mine's a Central American 12-volt 2H (1984).

Without booster the clutch master is 31410-60050 (subs 60051)

Found in Aug 80 to April 86 BJ4#, HJ47, FJ4#
Also in Aug 80 to Nov 84 BJ60, HJ60, FJ60

And the slave is 31470-60091
Found in August 80 to June 85 HJ47
Also in Aug 80 to Nov 84 HJ60

That is according to a search I just performed on the General Market

So I'd look for a boosterless HJ47 from August 80 to June 85 or a boosterless HJ60 from Aug 80 to Nov 84.

no 40 / 60 / 70 / 80 series I ever seen with no brake booster . ..

But this is the clutch David...

 

[Tapage]

But this is the clutch David...

my bad .. sorry ..

 

[lostmarbles]

I've been thinking about this topic since making my post above...

I decided to look at which slave should already be on this 1984 HJ60. And the EPC says it should be (assuming this HJ60 was built pre-November 1984) 31470-60091.

So it appears that boosted and non-boosted still use the same slave...

And the master you should already have there (according to the EPC for prior to Nov 1984) is 31401-60010 (subs 60020 & 60021)

So to change to non-boosted you apparently need to swap from 31401-60010 master to 31410-60050 master or 31410-60051 master.

(By the way, I am not mistyping when writing 31401 instead of 31410. That's what the EPC says.)

But I wonder what else you need to do (apart from throwing away the booster and connecting the new master to the pedal and fluid line)? Surely it can't be that simple?