Loss of vacuum and brake booster assist - help

[fester2au]

Hey guys, after sitting around in states of repair for over 12 months I finally got the truck driveable yesterday to find brakes are crap. I'm not getting any booster assist and the brake warning light remains on. Disconnecting the wire form the switch in the vacuum tank supports the problem as does the lack of assistance. Though it may have been the silicon hoses I used collapsing under vacuum not that you could see of feel anything but a return to the original hoses made no difference. The vacuum pump has not been touched and the whole system was working fine before. Also the vacuum triggers aroudn the engine all appear to be doign their thing so the pump woould appear to b generating vacuum.

Any suggestions on where and how to start testing. Got heaps of other stuff to still do even though it's ont he road as it's supposed to be going for a decent trip at Easter.

[Mulcahy]

Hey this has also happened to me and it was that the booster diaphram was perished and to find out you can either get someone to rev the car and you listen to hear for a leak or easier i found was to either blow into the vaccum line from the alternator and you should here a leak

thanks Shane Mulcahy

[fester2au]

Thanks Shane I'll add that to teh list to check but not sure if that can happen in this case. The 1HD motors have a seperate vacuum pump that builds vacuum in a reserve tank. This tank has a one way valve which would not let vacuum leak back through the booster if it were faulty. I fhe leak was only at the booster and the tank held vacuum then the brake light switch would not trigger. Also the tank is divided in 2 as the clutch has booster as well and it is not workign either.

[shorty_f0rty]

if you confirm the canister and hoses are all good its probably the vac pump. it has blades that slide in and out from the shaft as it spins and these can perish.

you have to break down the pump to get at the blades and can buy them from toyota for about 12$ each. there is a 3 and 5 blade vac pumps. I replaced the blades on my vac pump only to have them go again not long after. I think mine went because something was flogged out. I ended up getting a complete pump from the wreckers which has been going strong since.

ring around the wreckers as I was quoted prices from $80 to $180 for a complete pump.

removing and refitting is relatively straight forward for a novice.

[fester2au]

After some investigation today it turns out there was a blockage in the steel line between the pump and tank. Most likely a wasp nest of something, was really jammed in air would not shift it, hence no suck past that point.

Went for drive and better but after an initial brake application any subsequent ones are greatly lacking assistance, not as bad as originally but not great. Leave them for maybe 30 seconds to a minute and again 1 good application then average again.

Am I not getting enough vacuum maybe or do I have a booster issue as well.

[RAY185]

I'm with Shorty, your vac pump blades are probably shagged. They are only bakelite. They are still making vacuum but nowhere near enough. You can put a vac guage on it and see for yourself, see if you can compare your reading to another known working one (mates car?) if you can't find the original spec.

[shorty_f0rty]

forgot to mention that you should test your vacuum.. disco the line from the vac pump at the booster canister, run engine and put finger over the end of the hose to test vacuum. with mine there was bugger all sucking happening.. leading to pump issues.

[fester2au]

Done the finger test and it does hold my finger but without knowing how hard it should suck not sure if it's good or not, certainly not 16yo school girl good at any rate. Haven't found any specs anywhere yet to tell me what vacuum it should pull. Without finger sound is quite audible. Pump is not that old as engine is 1HD-FTE, think engine had only done about 80k's. Next thing is to check blades but be interestign to see if local toyota keeps them in stock.

Was going to make adaptor up to hook up old boost/vacuum gauge to check but nothing to compare to.

Can blow into booster for what seems like a while but sucking seemed much harder so I wasn't thinking booster problem yet and or course previously both clutch and brake was affected much the same.