Help troubleshooting clutch vacuum issue - HJ61

[Silveredition]

Hi all,
I have a 1988 HJ61 (12ht, 5 speed manual). Recently I have had issues with the clutch being hard to depress if used quickly between gears. This has got worse over the past month. The brakes appear to be fine...
First, I took the Vac pump off and had a look inside - all looks like new
Next, I connected a 12v vac pump and had the same issue
Both clutch and brakes hold vacuum when left sitting overnight

Yesterday, I swapped the brake and clutch vac hoses at the boosters, and the clutch worked fine (but not the brakes). I then swapped the brake and clutch hoses at the 'Y' diverter closest to the vac pump - and again I had a good clutch, but not good brakes. In doing this, I noticed that the 'Y' diverter has a direct hole from vac pump to brakes, and a restricted hole to the clutch (I assume to give more vacuum to the brakes),

When letting the clutch out, I notice that about half-way out it seems to lose its assist and becomes heavy - could the issue be in the clutch booster, only when it is being depressed?

Anything else I could try to troubleshoot before just replacing the booster? I have a vac tank on my FJ62 that I was thinking of trying, but feel I might be wasting my time?? Any thoughts would be greatly appreciated!!

Thanks heaps!!

Drew

 

[relaxedcruiser]

It seems you can rule out the pump, that is producing enough vacuum.
So can you actually say that the clutch booster is working fine when hooked up to the brake circuits hose ?
I believe that you can not limit the negative pressure by a restriction or orifice in the hose but you can limit the amount of air passing through it in the short moment the clutch is applied. Probably the "harder" impact of the vacuum when using the "open" hose helps to overcome a clutch booster issue.
There is a seal around the pin of the clutch booster which actually pushes the clutch master cylinder. I would thake the Master of and smear a bit off rubber grease around it. That could for a short time help that seal to seal. This could probably narrow it down to that seal / the clutch booster being foullty. That seal is part of normal booster overhaul kits - maybe you could even use a oil seal with the right dimensions.
Have you hooked up your electric pump to the small vac tanks or direct ?

 

[Silveredition]

It seems you can rule out the pump, that is producing enough vacuum.
So can you actually say that the clutch booster is working fine when hooked up to the brake circuits hose ?
I believe that you can not limit the negative pressure by a restriction or orifice in the hose but you can limit the amount of air passing through it in the short moment the clutch is applied. Probably the "harder" impact of the vacuum when using the "open" hose helps to overcome a clutch booster issue.
There is a seal around the pin of the clutch booster which actually pushes the clutch master cylinder. I would thake the Master of and smear a bit off rubber grease around it. That could for a short time help that seal to seal. This could probably narrow it down to that seal / the clutch booster being foullty. That seal is part of normal booster overhaul kits - maybe you could even use a oil seal with the right dimensions.
Have you hooked up your electric pump to the small vac tanks or direct ?

I did take the master clutch cylinder off (it is leaking a little bit, so I now have a new one ready to go on) and I smeared grease around the seal on the booster shaft - but it didn’t make any difference. I hooked the electric pump up to the line that goes to the vac pump on the alternator….
I have the new booster and clutch master, so might just install them and hope for the best!!

 

[relaxedcruiser]

Well, if you have them at hand it might just the easiest to replace them and hopefully everything is fine.
You need to adjust that pin of the booster to the master cylinder piston. The procedure is well documented but in short you want zero or about zero play. That pin must not push the piston when the clutch is not operated.