Please explain how the vacuum tank on 3B works? (1 Viewer)

[Awl_TEQ]

Only difference I can think of would be volume of vacuum available to the system? Does the small one have a port for the vacuum sensor idiot light sending unit thingy?

 

[RufusTheDufus]

Yes, has that sensor.

I'm doing the conversion you've done. Except I'm a few years behind. Going from HJ45 to BJ45.

I'm thinking the little round tank would be easier to deal with even though I have a brand new shiny Awl_TEQ tank on the shelf

I'll have to see how much of the original HJ45 vacuum hard lines I can reuse and base the decision on that. Just wanted to see if there was non-obvious functional reason the 40 series tanks are 5x the volume.

 

[RufusTheDufus]

Maybe the earlier vacuum pumps didn't draw as hard and required a larger volume to compensate for the lower vacuum?

 

[roscoFJ73]

Maybe the earlier vacuum pumps didn't draw as hard and required a larger volume to compensate for the lower vacuum?

I was thinking the same thing. I guess the secret would be in the vacuum pump and how much vacuum it can make.

 

[RufusTheDufus]

I've switched to the NPR style alternator and it produces quite a bit of vacuum. Maybe I'll go with the little tank.

 

[Yellowknifer]

I actually have the little tank from a 70 bolted up right now to my bj42 and it doesn't produce enough vacuum. I run out after one or 2 stops usually.

 

[RufusTheDufus]

I've been running the little tank with the NPR alternator for a couple weeks now. It seems normal to me. The brake system works the same as it did with the stock frame-mounted tank and the same alternator.

 

[Yellowknifer]

I actually just replaced the little tank with the old one I fixed and my brakes are back to normal. Maybe my little tank had a leak or the stock pump isn't enough to keep up?

 

[45Dougal]

Hi;
Newbie here, so sorry to dig up an old thread..
My HJ45 has no vacuum pump or reservoir, but the servo is connected to the inlet manifold. The brakes are very hard.
I can see that it should have the huge oval tank under the floor, and the pump on the alternator (both have long since been removed).
I'm not a purist (yet) so I'm planning to install a modern electric vacuum pump, and a modest reservoir, and my question is this:

Can anyone please tell me how this was originally all plumbed together?
Is it just a simple pipe connecting Pump-Tank-Servo with no valves?
Is the manifold connection needed, or was this just added when the pump was lost, and should I just remove this and blank it off?

 

[roscoFJ73]

Is it just a simple pipe connecting Pump-Tank-Servo with no valves?

Yes, the pump should have a built in valve that senses how much vacuum is in the tank. When there is enough it stops making vacuum.
Diesels don't make a lot of vacuum in the manifold , this is why they have the vacuum pump . Its also why your brakes are very hard. So, block it off.

 

[45Dougal]

Yes, the pump should have a built in valve that senses how much vacuum is in the tank. When there is enough it stops making vacuum.
Diesels don't make a lot of vacuum in the manifold , this is why they have the vacuum pump . Its also why your brakes are very hard. So, block it off.

Ahh right, thanks! My electric pump and tank just arrived so great timing

 

[roscoFJ73]

I dont know about your electric pump. I was referring to the OEM pump that was originally there

 

[alberta mac]

There is a possibility that you have a micro rust hole in your reservoir. If you do not have the power to brake, it just doesn't feel right then the two hoses that connect to your tank need to be removed and connected to each other creating a loop. Then go for a short test drive and see if the first or second pump is like normal. If yes then there is a hole in your reservoir tank, I have a plastic one from a vw on another truck that works, on a 60 series they are much smaller and mounted on the dash. My preference is to mount them under hood if you go off-roading. If not you could easily build one with pic and glue.