4bd1 Vacuum issue.

**ozeraser** · 9th February 2016, 06:11 PM

Afternoon all,

Long and short of it, 4bd1 powered 2A.

Yesterday I noticed rather than the standard 20-25ish psi on the vacuum gauge I'm seeing 10 -15 (higher revs higher psi).

The vacuum pump is on the back of the 12v alternator, which then goes to another servo operated junction near by, this then goes past a T piece for the vacuum gauge and into a brake booster.

The only odd thing i noticed was when i was idling in the driveway if i depressed the brake the PSI would increase not decrease as i expected.

Additional info the hydraulic clutch as been a little stiff as of late, and the brake fluid (that goes to both brakes and clutch) has dropped about 1/2cm. I followed all the rubber vacuum pipes and none appeared to be collapsing or leaking (by feel)

I was planning on disconnecting the vacuum pipe from the booster and closing it off to see if it makes any difference with the PSI. (However the booster is in a really inaccessible place). Just though before i cut my hand to pieces trying to disconnect any one got any ideas/thought etc?

**JDNSW** · 10th February 2016, 06:40 AM

Most likely the booster body is cracked near where it mate to the master cylinder.

John

**rar110** · 10th February 2016, 08:03 AM

A small leak in the booster diaphragm?

Break fluid leaking into the booster causes deterioration.

**ozeraser** · 11th February 2016, 05:23 PM

Thanks guys, So i was troubleshooting this afternoon, mainly cause there is a big trip tomorrow and hopefully it will survive the journey.

So from what i can see is the brake master cylinder then pipes to the top of the VH44 brake booster, which then runs off to the brakes. Does that sound right?

What I did was i put my foot on the brake and the vacuum built up, then turned the car off (so i can hear) and released the brake, vacuum escaped. The hissing seemed to be coming from the master cylinder, does this sound like a possibility or do i need to take another listen?

Also if this fails completely i read that it should just be harder to brake (not assisted) but the brakes should still work. Can anyone talk to this?

**rar110** · 11th February 2016, 09:05 PM

The vacuum hose should run from the back of the alternator to the booster chamber. Check the hose and joins first for anywhere air might get in.

You can drive without the vacuum assist. However it feels a lot different. You need to push a lot harder. It will feel like the brakes don't work.

**flagg** · 11th February 2016, 09:41 PM

Originally Posted by rar110

You can drive without the vacuum assist. However it feels a lot different. You need to push a lot harder. It will feel like the brakes don't work.

a LOT harder.. I had this happen once and it was (IMO) dangerous.

**ozeraser** · 11th February 2016, 10:29 PM

Yep no problem called off the trip better to be safe

**JDNSW** · 12th February 2016, 05:15 AM

Originally Posted by flagg

a LOT harder.. I had this happen once and it was (IMO) dangerous.

If it has a VH44 booster, it was designed to operate without a booster, so the loss of boost will not be as significant as it is, for example, with a 110. The drum brakes on the 2a have two leading shoes on the front, lessening pedal pressure compared to the discs on the 110, that have no servo effect.

John

**ozeraser** · 12th February 2016, 08:27 AM

Yeah, thanks guys i will keep you updated on what i learn

**ozeraser** · 25th April 2016, 10:45 PM

Howdy all had a week off and finally got to give the girl the time she needed, I think the car was rebuilt around the booster as it was in a hell of a spot to get at (driver side corner). Whilst i tested the main hose going to the alternator vacuum pump the issue was actually a split hose going from the back of the booster to the underside of the master cylinder on the brake booster.

So I grabbed some spare vacuum hose i had from my old VW beetle, and she was all good, i have since got the correct part for $6 but it will take a good 2-3 hours to fit it, and it can wait.

Thanks all :P

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