Brakes take a break!

[Hound]

My brakes have started acting weird in the last two days.

Under normal driving conditions, they work fine. When reversing, they work fine.

Sporadically, when creeping forward in D or neutral, at a snail's pace with little or no throttle, the pedal sinks and there's no discernible braking at all. One pedal pump and it's back to normal.

It only happens at slow speed, eg car park, and as I say not consistently - and never in reverse gear.

Dying master cylinder or seals, or a vacuum problem? (The brake fluid level is fine.)

Thanks for any insight.

[stribo]

Sounds like it could be leaking internal seals in the master cylinder, as it's only happening when you press the pedal gently.

[JamesT5]

My brakes have started acting weird in the last two days.

Under normal driving conditions, they work fine. When reversing, they work fine.

Sporadically, when creeping forward in D or neutral, at a snail's pace with little or no throttle, the pedal sinks and there's no discernible braking at all. One pedal pump and it's back to normal.

It only happens at slow speed, eg car park, and as I say not consistently - and never in reverse gear.

Dying master cylinder or seals, or a vacuum problem? (The brake fluid level is fine.)

Thanks for any insight.

Perhaps the brakes need bleeding, try that first.

[oblark]

Sounds like a small vacuum leak on the servo.

When the engine is at low revs it cant draw enough air out of the servo to get a vacuum but at speed it can.

[Hound]

Thanks for the input guys, I will get it looked at. Intermittent problems are so annoying!

[Hound]

Update: Rats. Found oil emulsification in the dipstick tube. Did the rubber glove test on tube and oil filler and it's definitely blowing some pressure out when revved, instead of sucking. Compromised vacuum on brakes at low speed could well be because of the PCV system being partly clogged with emulsified gunge.

Now I have to have a compression test and get the head gasket checked out. The expense of getting it replaced it could well be unviable considering the car's age and value.

Not pleased considering I've only been driving it since October!

[Jamest5r]

The head will be fine all old volvos have moisture on the dipstick, very common to see mayo on your dipstick, don't worry

[Hound]

Thanks James - my mechanic just said pretty much the same thing. He thought a compression test was probably not necessary but he will assess it when he sees and hears the car. He also says my problems with the car running cold will likely have contributed to this. At least I have diagnosed the PCV issue though - apparently common. I'm now a bit more optimistic about the head gasket -- cheers!

[Jamest5r]

The pcv is easy enough to do with a general socket set, if you take your time 1st time you'll do it in about 3 hrs and the parts are about 100 odd quid.

[Hound]

I'm not able-bodied enough to do the job but have seen a pretty good YouTube vid of it, and it looks reasonably straightforward... fingers crossed!

[Nealevo]

If I can do it then anybody can, it took me 2 and a bit hours, my engine was out of car at time so I had it easy but it's very doable.

[Jamest5r]

If I can do it then anybody can, it took me 2 and a bit hours, my engine was out of car at time so I had it easy but it's very doable.

Your having a laugh...... 2 and a bit hours with the engine out???? should of taken 20 mins

[Nealevo]

I was waiting for you to turn up 2 hours late, remember, so it did take 20 mins lol

[Jamest5r]

I was waiting for you to turn up 2 hours late, remember, so it did take 20 mins lol

Nope I was on time Smithy was late as usual, actually lucky he turned up at all in daylight hours

[Hound]

I doubt it would be viewed favourably in the Hound household if I had the engine on the dining room table for easy access! Back in the day I had all sorts of bike engines and car cylinder heads indoors to work on...

No garage either so I think the wallet's going to take a clobbering.

[Jamest5r]

I doubt it would be viewed favourably in the Hound household if I had the engine on the dining room table for easy access! Back in the day I had all sorts of bike engines and car cylinder heads indoors to work on...

No garage either so I think the wallet's going to take a clobbering.

I'm not sure what the book time is for garages for this job can't see it being more than 2 hrs

[AndysR]

With the dipstick being right at the front the engine it's not uncommon to see a little bit of Mayo in the tube due to the tube being cooled by the flow of air through the car as you drive. I probably wouldn't worry about what you've found other than to keep and eye on oil and coolant levels regularly and to get the PCV system checked/replaced as required.

[Hound]

I'm now not so sure of my theory that the brakes are affected by the breather issue, so this thread has perhaps strayed off-topic a bit, but thanks as always to you chaps with your prompt and sagacious advice!

[stribo]

I was thinking that too, the other thing to check would be the non return valve to your servo.

[Saaamon]

Have you followed up oblarks advice?