345 low on vacuum

Well I finally got some gauges hooked up and the vacuum,12 hg at idle , stab the accelerator and goes to Zero, the only thing that is an unknown is if the vacuum tank are full or filling , I’m guessing if the tanks were filling it would affect reading at the gauge , some one in a previous life decided if you cut the wires including the one behind the dash including the brake light .
if I rip and cut then there isn’t a problem....., I had a funny feeling that the vacuum would be low , there’s 2 one inch hoses going to the twin vacuum tanks , another 2 little hoses for the pollution bizzo , one for the recycling the fumes and one for the distributor...... I’ve probably missed something but those will give you an idea, ive replaced every hose I could find And I’ll have another look, is the 345 known for low vacuum ? Or is this pretty typical?

Obviously something wrong somewhere .....the motor wouldnt even idle properly with lees than 18" vacuum.......I would suspect there is a restrictor in the manifold takeoff ,combined with leaks in the brake system............Test the vacuum in the manifold ,with the fitting removed ....one cause of low vac in the motor is retarded ignition timing ....might also explain high fuel consumption........If you have a timing light ,check the timing with the engine running.

Well I was quite excited to use my new (10 years in the cupboard) got it out annnd it doesn’t work, I’ll get one off flea bay and start again

So I took the vacuum double piggy back and found a spot to feed straight off the manifold, tightened up every hose i could find big or small and even put speed clamps on the vacuum lines on the motor, started her up and now it’s 17” hg at idle. I’ll wait for the timing gun and take it for a drive

Now that really sucks.

Hey out of curiosity cobba, when you had problems with keeping your tanks full? Or empty ? How long did it take too fill them? I’m wondering if it’s not quite full vacuum because the tanks hadn’t filled (or empty)

From an overnight park it would take about 2 minutes, over an hour about 1 minute but after a 5 minute stop it also took about a minute so it doe have a leak somewhere and I will get back to that soon enough as Lorry is having a rest with all the Rallies cancelled at the moment. It was suggested that a valve near the front of my tanks may be the offender. If it was the vacuum pump itself it would not build up at all. All the straight sections of hose have been replaced along with new hose clamps to ensure a good seal.

Ok thanks mate , I have no idea how long till they are full( we’ll call them full ... of nothing lol)
It appears that the light and buzzer must have annoyed one of the previous owners has erased the light And I’ve been looking for it so I know it it is actually full , and that In turn would drag the vacuum down whilst filling, the dash isn’t quite done yet so maybe it will narrow my search!

I do know that the light and buzzer work well in Lorry. One time I had a hydraulic line blow out when Lorry was fully loaded and the caravan hooked up as well going down hill and the exhaust brake was not holding so I touched the brake pedal, the bloody thing went off and scared us both. SO down through the gears and pull over.

I imagine they would have been like a car , they all have the dual system and I’ve never had trouble in 40 years and the only reason the a acco has is a brake cylinder is leaking on a cylinder on the diff , old mate that owned it was only using it in the paddock and it had been sitting for about four years , I’m not sure if the new trucks about our size are still hydraulic or on air ?