When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Ok so I believe my brake booster is leaking. I when I'm driving I get one really good solid stop. But if I try to brake hard again a few seconds later, I have very little brake assist. The pedal is firm, but it takes alot more effort to get the car to stop hard. Then if I drive for another minute and try to slam on the brakes, I have power assist again. So I believe what is happening is there is a slow leak in the booster so it takes longer to reach vacuum when running.
Can I test it by hooking my vacuum pump up to the line as shown in the picture below? Because when I do I get no vacuum at all.
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
A quick check is after shutting the car off, wait a few minutes and pull the vacuum fitting that you have circled from the booster. If you hear air rushing into the booster it may be functioning properly. If not, its probably leaking. Hooking a vacuum pump like you show in the pic will work too but may require a lot of pumping to get a vacuum. Pump it to 10" vacuum and see if it holds.
The Booster itself seldom causes issues but the vacuum fitting on the front can be a hit or miss. Should be a gasket on that plastic fitting.
And yes, your Vac tool should not only pull but barely hold vacuum for a few minutes. That's just the way those fittings are. They are not 100% perfect seal.
Perhaps your brass reducer / adaptor is the leaker here. I know you hate to cut that new hose but that's an awful lot of hose to pull a vac through.
Last edited by HeadsU.P.; Jul 31, 2018 at 09:15 AM.
A quick check is after shutting the car off, wait a few minutes and pull the vacuum fitting that you have circled from the booster. If you hear air rushing into the booster it may be functioning properly. If not, its probably leaking. Hooking a vacuum pump like you show in the pic will work too but may require a lot of pumping to get a vacuum. Pump it to 10" vacuum and see if it holds.
Ok I'll give that a shot. Thanks!
I've had a very annoying surge at low speed right as I'm letting the clutch out from a stop. Wideband 02 shows that the car goes momentarily very lean before settling back to a healthy A/F ratio. No matter how much I adjust my Idle mix and APT settings, I can't get that lean surge to go away, so I'm hopeful that a vacuum leak is actually the issue! Makes sense with my current brake booster woes.
The Booster itself seldom causes issues but the vacuum fitting on the front can be a hit or miss. Should be a gasket on that plastic fitting.
And yes, your Vac tool should not only pull but barely hold vacuum for a few minutes. That's just the way those fittings are. They are not 100% perfect seal.
Perhaps your brass reducer / adaptor is the leaker here. I know you hate to cut that new hose but that's an awful lot of hose to pull a vac through.
For sure, I'll double check that. Is there an easy way to isolate whether it is the actual booster or just the fitting on the front of the booster?
sounds to me like you do Not have vacuum reserve = leaks, not allowing vacuum tank can to to hold vacuum for a duration of time.
to fix get vacuum gauge , test and find leaks.
Can I test it by hooking my vacuum pump up to the line as shown in the picture below? Because when I do I get no vacuum at all.
Here is how to tested my Booster. You can do the same while on the car. This unit I was not able to get any vacuum build up. The replacement I could easily get 18 HG and it would hold it without a noticeable change after 60 minutes.
Testing Brake Booster for leaks
