What's this for/do?

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PeterC

10 Year 15 Year
Joined
Apr 26, 2006
Threads
20
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53
Hi All,
I can't figure out what this big canister thingy is underneath my BJ41.
It's about the size of a toaster. It is under the floorboard on the passenger side (RHD). It has a sensor of some sort coming out the back and a couple of hoses going in the front.
It looks like it might be emission related but I don't know how.
Any ideas?
Thanks,

PeterC
 
correct me if I'm wrong

your probably refering to the vacuum canister, it holds up air for your brakes in case your engine shuts down while going 90 on the highway! Mine is by-bass! (rusted out)

hope it helps a bit...
 
Yup, it's the vacuum reservoir for the brake booster. The sensor is activated if you lose vacuum (from a leaky air line, or damage/rust through) and will light up the "Brake" warning light on the dash.

Personally, I wouldn't remove it as it is a safety item. Imagine going down a long hill and losing power. The reservoir gives you brakes for a whole lot longer than otherwise.
 
The vacuum reservoir does give power assist to the brakes (remember Diesels don't make significant vacuum). Due to it's size, you get quite a few brake applications after the engine has been turned off.

In the '79+ bodies (with the raised floor) there's ample room under the hump that the driver's seat bolts to. You could relocate your reservoir as simply as using a flat plate of steel around a foot square, bolted to the inside surface of the frame rail, and extending up into the cavity under the driver's seat. Bolt the reservoir to the top of the plate, and extent the vacuum lines. Voila! No more hangy-down parts under the truck. (at least Mr.T put a skid-plate there to protect it)


Please don't remove the reservoir and 'get rid' of it. If you notice no ill-effect when it's removed, that is a warning that your brakes are malfunctioning. I recall posts regarding simple tests for you brake booster diaphragm, as well as your vacuum pump (located on the back of your alternator). Give it a search.

I think it's one of the things I like about the trucks. My brother, the mechanic, still gets amazed with some of the systems on the cruisers. They aren't always the best or most modern system, but they combine redundancy with simplicity, and I can dig that!

cheers,
Steve
 
Thanks for the replies. I have no intention of getting rid of it. It doesn't seem to be rusted out and with the exception of lift, tires and Line-x the truck is stock and bitchin. Plus, brakes are a good thing. It's also tucked pretty high up so it is definitely not in danger considering that, for me, four wheeling is simply what I sometimes have to do to get where I'm going.

Thanks again,

PeterC
 
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