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Vacuum Pressure Loss on Brake Booster

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drbjr71
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Vacuum Pressure Loss on Brake Booster

Post by drbjr71 » Wed Jun 15, 2016 9:07 am

Hopefully someone here can help me out!

I have never posted before, but have used this site to fix many things on my Volvo.

Anyway here is my problem. I had a my right front brake caliper sticking shut and rubbing against my rotor. I found this out after changing my suspension when I took the car to get aligned. So I decided to replace all of the calipers since they were all looking ratty. While my wife was helping me to bleed the brakes, and I was at the left rear wheel, the 'new' right front caliper leaked at the seal and the fluid in the line drained. Also, the reservoir and master cylinder went dry. Got another caliper for the right front and bled the brakes in accordance with VIDA LF,RF,LR,RR ignition off. Test drove and the brakes felt spongy. OK, Bled brakes again. Next test drive, went out and booster felt like it wasn't holding vacuum, but also read if pedal is pushed to the floor, you could break the seal in the master cylinder. Next replaced master cylinder, test drive and better braking but problem still persists. I have normal braking between at low speed ( below 20mph) and highway speeds (above 45mph). The brake pedal vibrates and goes to manual braking. If I pump the brakes several times the vacuum comes back to the booster and I have normal braking. Of course by this time my speed is also decreasing and getting back into the low range.

Also at this point on the 2nd test drive, car goes into 'limp mode' and throws codes with CEL. Put it on my OBII reader, code 1234 and 11-something. Anyway could be TCV, MAP Sensor, O2 Sensors. OK replace them all with Bosch and genuine Volvo parts. Clear codes, codes don't come back move on.

OK back to brakes. I come back to Matthews and posts state it is the Booster. OK, I get a genuine Volvo booster and ejector and replace them. Still have same problem. Also since I change the TCV, et al, turbo jumps up RPMs to 4000 to shift from 2nd to 3rd gear. Not sure if related or not.

I read an old recall that claimed that master cylinder/reservoir problems could occur and both should be replace. OK went and bought a genuine reservoir.

I am really stumped on what my problem is? I see that vacuum line for the booster runs into the intake manifold. I checked the lines and no cracks. The booster feels like it works normal and then loses vacuum. Could this be a vacuum problem? If it is, would a bad ETM also change the vacuum makeup in the intake manifold and steal vacuum from the booster? Or when the master cylinder went dry, did I screw up the control unit or the ABS pump? Is there a relay somewhere besides the solenoid on the booster that might cause the problem? Basically everything on this braking system is new except the ABS pump and the Control module. Because of the tranny issue and the brake issue, I wondering if they might be inter related?

The car just turned 100,000 miles.

Any help would be a 'God send'

Thanks

scot850
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Re: Vacuum Pressure Loss on Brake Booster

Post by scot850 » Wed Jun 15, 2016 11:32 am

The brake system can be a bear to get all the air out, even using the Volvo recommended process, especially if the ABS pump has been drained.

It may be worth taking to a repair shop to have the brakes pressure bled, or purchase a pressure bleeder. I think you have replaced parts that were probably not a problem.

The master cylinder can leak into the booster casing, and I had this issue with a 98 V70XC, but I knew it was a problem also could smell the brake fluid. Dealer said I needed to replace both, but there was nothing wrong with the booster. I replaced with guaranteed used parts from a specialist Volvo supplier.

The other issue that can happen is there is a valve in the booster that holds a vacuum in the booster for when you need it. These can fail and are typically a plastic part at the front of the booster where the booster vacuum pipe from the engine connects to. I would suspect that would come with the new booster. When that fails though you tend to get a hard peddle with little retardation - scary!

There is sometimes a little filter in the vacuum line from the engine to the booster that can clog, but again nothing to suggest there is a vacuum issue.

Long story short, have the system professionally pressure bled and check all the bleed screws are tight and there is no fluid leaking out anywhere.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
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drbjr71
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Re: Vacuum Pressure Loss on Brake Booster

Post by drbjr71 » Wed Jun 15, 2016 12:44 pm

Thanks for the response!

I do agree, I probably replaced things that didn't need to be replaced, but I'm also looking at this as a restoration because I'm never parting with the car, so the new parts aren't an issue.

Anyway, the second brake bled was with a power bleeder. I used almost 2 qts, so at least I flushed the line.

I didn't know about the vacuum filter in the line so I'm going to take that apart and check all the lines, plus I ordered a vacuum pressure guage to test.

I'm assuming the plastic valve you are talking about is the check valve? The new booster came with a new check valve, plus I ordered another because when you order from Volvo, they break it out into different parts. I didn't know the new booster would come with a check valve. I might just change it and see if that works.

Also I forgot to mention that my car has STC. I didn't realize that at first, but I've seen where others have posted you need to get a different booster. When I go to Volvo online they only list one booster for the car. The part numbers are different from the one I changed vs the new one, but I assumed this was an updated part. I don't know if this matters or if something with the STC is malfunctioning. VIDA doesn't mention anything about this either.

Also I know VIDA says to keep the ignition off when bleeding, but someone also told me that you have to have the ignition turned on for the pump to feed. Don't know if anyone has heard of this or not, but we'll try this also.

Unfortunately, I'm an American living in Germany and auto repair procedures are different than in North America plus a little bit of a language barrier.

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Re: Vacuum Pressure Loss on Brake Booster

Post by abscate » Thu Jun 16, 2016 12:38 am

STC doesnt chamge the hydraulics i think you just got air in it and might still have air in the lines.

vacuum leaks will give that check engine light as well as the changing pedal feel, so thats where you have to hunt down.
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