new brake servo bad?

[NickDawson]

Hey folks,
Just installed a new booster from our hosts. My old one was bad in that when you depressed the pedal it leaked air, the vacuum would drop a little...

This one is just hissing non stop and the in-dash vacuum gauge dropped way low. If I pull the hose off and plug it with my finger, the engine smooths out and everything is fine.

It doesnt appear that the air leak is at the hose or the 90 degree valve - although the 90 degree valve is quite lose and comes out with a good tug. It is coated in grease and seems to make a good seal when re-fitted.

So, is there some part of the install that the green bible doesnt cover that I should know? Do I need some kind of gasket somewhere, is there some kind of priming that has to occur or is this thing just leaking air like a sieve because its faulty?

[jac04]

It looks like you've isolated the vacuum leak to the new servo, so it appears that you have a bad part. Every time I've installed a new or used servo I've just bolted it in place and hooked up the vacuum hose. Never any problems.

[NickDawson]

Thanks Jac04 - nice to have a 2nd opinion, also wanted to make sure there wasn't a missing step.
I'll ship it off for a replacement and try again.

[I Leak Oil]

If I remember correctly mine had a small pipe plug type screw in it. When I bought a new one it didn't have it installed so I had to use the old one. I think it was on the bottom front face of the servo.

[SafeAirOne]

If I remember correctly mine had a small pipe plug type screw in it. When I bought a new one it didn't have it installed so I had to use the old one. I think it was on the bottom front face of the servo.


Funny, I was just looking at mine the other day and wondering what that plug (or rather the hole that it plugs) is for. Like Jason says, make sure your new one has this plug installed under the Master cylinder:
http://farm5.static.flickr.com/4013/4714971829_41dbe2a62b_b.jpg

[I Leak Oil]

Geezzz Mark, do you have photos of every square inch of your truck?! The only thing I can imagine this is for is a vacuum gauge fitting of some sort.

[jac04]

It's for a vacuum loss brake warning light switch.

[SafeAirOne]

Geezzz Mark, do you have photos of every square inch of your truck?!

Ha--No, but my rover is 2 steps outside my front door and I keep the camera halfway between the computer and the rover. I've got it down to about 2 minutes between snapping the picture, resizing it, uploading it to flickr, then linking to it in a post.



A vacuum failure warning switch, eh? Makes sense...

[NickDawson]

Funny, I was just looking at mine the other day and wondering what that plug (or rather the hole that it plugs) is for. Like Jason says, make sure your new one has this plug installed under the Master cylinder:


YEP! Sure enough, there was a small threaded hole in the bottom. With some PB blaster and elbow grease I was able to get the plug out of the old booster and install it in the new one. That fixed the vacuum leak, sorted out the engine and now the thing is stopping better than ever.

Thanks SafeAirOne!

I triple checked the box from our hosts, the screw is not t be found. Hummm... I'll give 'em a call on Monday just so no one else has the same issue (although, most of this crowd would have been smart enough to check/see that in the first place ;) )

[SafeAirOne]

Thanks SafeAirOne!


Don't thank me--Thank Jason (I Leak Oil). I just took a picture of what he was talking about.

I suspect the servo comes without the plug. They expect you to supply your old one or a new one, just like some alternators come wiothout pulleys and you have to swap your old one onto the new unit.

Glad to hear your brakes are sorted out. :thumb-up:

[Opabob]

the Proline servo I just order has metric threads. the original servo has English threads. I assume though, the threads for that plug will be the same once I manage to get the old rusted one out so I can use it, right?