2H Vaccuum Question

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Jan 23, 2008
East York, Canada
I have a question about the vaccumm system. I have a 2H diesel so the vaccuum for the power brakes and clutch is supplied by the vaccuum pump on the rear of the alternator.
My question is it normal for the vaccuum to bleed off from the system when the engine sits for, say overnight.
In the morning when I go to start the engine and step on the clutch all the vaccuum has gone from the clutch as the clutch requires more effort to step on.
Also as the engine is running and supplying vaccuum to the system if I step on the clutch say 5-6 times real fast it (clutch pedal) starts to get harder to depress. Then if I wait a few seconds the vacuum I guess replenishes and all is normal again.
Is this normal?
oddly enough I've been going after this same gremilin myself. I'm putting money on it being a bad hose/connection and hopefully not a sign of a bad seal in the alternator, but in all honesty I'm pretty stumped. Mind you I haven't actually gotten in there and really checked much out.

Is it the same vacuum setup for the brakes and the clutch. On my 40 when this happened to the brakes I checked the vacuum tank and it had a big gapping hole in it.
Not really adding much here, but maybe yours and my problems are on par?
There is a vacuum canister that supplies both the brakes and clutch. I did have the alternator and vacuum pump removed from the engine last week when I replaced the alternator brushes. The pump looked like it was in good condition. The o-ring seal between the pump and alternator housing looked ok. When I spun the alternator with the pump installed it seemed ok. When I reinstalled the lines from the pump to the vacuum canister I made sure the spring clips were put back on.
Is there some way of determining if vacuum is leaking from the system? Anyone?
you could fit a vac gauge to the vac tank and inspect fo overnight bleed off but I assume that the vac gauges are fairly $$$.

We had one on the shop a couple of weeks ago with a simular prob, the vac was not dropping fast enough. 3-5 pumps of the clutch/brakes with engine ideling and the low vac buzzer sounded, tested and showed that the vac was not working properly, fitted a new alt/vac pump, and wha-la......same thing, removed all intake hoses to the vac pump and found a wasp nest (mud and gunk) restricting the ammount of available air to the pump.

proberly not your situation, but if anyone has an alt or vac disconected for any ammount of time, check for restrictions, its cheaper than getting a new pump 1st
actually good point up there jus cruzin. When I checked the vacuum tank on my 40 it had a bit of oil in it, so the gunk is probably a likely cause. The other thing I'd check, and I learned this the hard way, is to ditch those spring clips and go with standard ss hoseclamps. The springiness of the clips tends to wear with time. If I figure this one out on my truck I'll let you know what I did.

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