Tech question- Brake vacuum supply from Diesel engine?

[Brewsterfire]

Hi everyone
I need to know how the vacuum to the brake booster is connected to the diesel system. I am installing a 13BT in a 1971 FJ 40.

TIA

 

[doug720]

Three choices:

1) Vac pump on rear of alt

2) Electric vac pump

3) Hydroboost brake system

Diesels don't have vacuum, so no source to use for brakes, other than listed above.

My swap used the Isuzu 4BD2 engine which has a alt driven vacuum pump on the back stock. Many Toyota diesels used the same type of alt-pump combo.

Simple, reliable and easy.

You can find them online, but I don't know any Toyota part numbers.

 

[rick_d]

13bt is on back of alternator traditionally. Vacuum runs to reservoir, then to brake, clutch, ac idle up, and shut down vsv. Used 70 series reservoirs are common but you can fab anything (icky used a propane cylinder). 70 series right fender and firewall crossover pipes are US items or you make one to jump from vacuum pump to reservoir to brake booster. 70 reservoir is placed in notch between firewall and right fender (in a 40 it would be below fan unit).

 

[Brewsterfire]

Thanks Doug and Rick
I was trying to figure out how to get to the size of hose on the brake booster as it is like a 1/2 " hose. The reservoir would allow the size of hose increase.

 

[lostmarbles]

And here's the layout of the vacuum piping on my BJ40:

Note that there's a vacuum reservoir mounted under my floor.

There's a warning buzzer to tell me if my vacuum level is low and that reservoir is able to maintain a satisfactory vacuum even if my BJ40 has been left for a month unused.

 

[Brewsterfire]

Thanks Tom for the visual, helps a lot.

Cheers!

 

[lostmarbles]

Thanks Tom for the visual, helps a lot.

Cheers!

Here's how it is for a left-hand-drive:

That might be better still for you..

 

[Brewsterfire]

Thx, got to go parts hunting.

 

[ozcrusier]

No just get some 1/4 copper pipe and bend to suit your firewall as required and then paint silver if your after the stock look.

 

[Past it]

Here's how it is for a left-hand-drive:
View attachment 1059443

That might be better still for you..

Hi Tom, Was mystified with my 1983 LHD bj42 vacuum supply to brake servo until I read your thread with diagram. My resevoir was missing. Can you suggest what result I would get if I directly coupled the pipes together (temporarily) and where would the resevoir be mounted. ( I guess on the chassis left of the fuel pump).

 

[roscoFJ73]

and where would the resevoir be mounted. ( I guess on the chassis left of the fuel pump).

Not sure if Tom still comes here. You can mount a vac reservoir anywhere it fits. Toyota put them in various place for different models, sometimes on the opposite side to the brake booster like the on the 105 series. But I think as close the booster is possible is best.
Most of the newer models were mounted in the corner where the firewall meets the fender.

 

[Past it]

Thanks Rosco . The diagram explains all. Oh for a manual! However, anyone know if brakes function ok without the reservoir in the circuit?

 

[roscoFJ73]

anyone know if brakes function ok without the reservoir in the circuit?

I don't think they will, the vacuum pumps usually stop supplying vacuum at negative 6psi. But Ive never tried it. But the other problem is if you your engine stops, so does your brake pressure. As its names suggests, it is a reservoir, it will give you a couple of stops before it is depleted.
Its quite possible you could use another reservoir from any diesel until a 4* series reservoir comes along,
Put in " vacuum reservoir diesel" into ebay and you get a few used and new reservoirs off various makes.

 

[Past it]

Thanks Rosco, have promise of one at end of month. May try it out without one to see result, in safe area of course.