760 Intermittent Soft Brake Pedal

I had rust on the booster shaft but as well my r/h side caliper was sticking so a simple pull down regrease and clean fixed all . Make sure your sliders and calipers are greased with lithium based brake grease ,they should move easy when you push them . Have some one watch while you activate the brake pedal after pushing them back in with a clamp . It could be your master cylinder is worn as well . Does your steering pull either way when you stop ? Every so often I activate my ABS as I have heard they get lazy when not used as normally they are passive except when extra strong braking is used . How long since you bled your brakes with new fluid ? Good fortune and happy Volvo-ing

The brakes seem ok, I don't think there's any sticking going on, it's been like this for "years"! If it was the master cylinder would it not be bad with the engine off as well? And yes, I could do with new fluid but would that not be permanent also? What was the effect of the rust on your booster shaft, did cleaning help, could you clean it? Bob.

Mine played up when the car was used in heavy traffic and when hot then later at any temperature still later the callipers were sticking due to over heating . The rust on the booster shaft is apparently an issue all I know is greasing the shaft seemed to make a difference but when I used lithium grease all round no more issues .

Thanks John, it looks like I need to go and grease my shaft then! I was rather hoping that there might have been a bit more information about as it's supposed to be a fairly common problem, just seems everyone is keeping quiet about it. Does anyone have an exploded view of the booster for a quick look before I dive in, or should that be try and fit myself in under the dashboard? Regards, Bob.

Family newsgroup, buddy!

Hi Tim,

Please accept my apology if my remark offended you, it certainly wasn't meant to, it was just a flippant statement of fact.

More light-heartedly if I may please, in the UK this probably wouldn't qualify as a family newsgroup as anyone under the age of about 50 who mentioned the word Volvo would probably be looked upon as needing to see a psychiatrist to help them with their premature ageing. Volvos are very often seen as dull and boring, more of a safety concious older persons car in the UK.

Regards, Bob.

No apology necessary. "Family newsgroup, buddy" is a standard Usenet joke tossed out in response to a double entendre, not an indicator of actual disapprobation. Perhaps I should have included a ;-)

LOL! Much there same here in the US. Volvos- especially the 240-740 models- have two images here: one of stodginess and the other of left wing liberal politics. They are stereotypically seen here as being driven by college professors and old men wearing hats, especially by the nattering nabobs of negativity that infest the American right wing of politics.

It was summed up neatly here:

I don't know about the UK's political process, but this is representative of the typical level of political discourse in America. I think it explains a lot about the last 30 years.

Cheers!

I'm glad you're smiling Tim, I was getting a bit concerned for you mental wellbeing for a while!

Had a look at the uTube but I can't imagine UK Volvo owners being too interested in Lattes or Sushi, I think they tend more towards vegetarianism nowadays, going back 20/30 yrs to the 2's and 7's you could always recognise the Volvo owner as he [never a she] always had a hat on [not a flat one] and probably a pipe on the go with a very thick outdoor coat on. They were just about the most dangerous people on the road, I think the theory was it was a safe car so I'll do what I like in it!

Volvos, like a lot of European cars must have come as a bit of a culture shock to some people in the USA all those years ago, you know, safe, go round corners, stop ok, rubber tyres, reasonable economy, etc. The latest Volvo TV advertisement over here describes them as "Sexy", they're looking for a new image!

Have a good weekend, I'll post the outcome when I've got my shaft cleaned and greased.

Regards, Bob.

No apology necessary. "Family newsgroup, buddy" is a standard Usenet joke tossed out in response to a double entendre, not an indicator of actual disapprobation. Perhaps I should have included a ;-)

LOL! Much there same here in the US. Volvos- especially the 240-740 models- have two images here: one of stodginess and the other of left wing liberal politics. They are stereotypically seen here as being driven by college professors and old men wearing hats, especially by the nattering nabobs of negativity that infest the American right wing of politics.

It was summed up neatly here:

I don't know about the UK's political process, but this is representative of the typical level of political discourse in America. I think it explains a lot about the last 30 years.

Cheers!

Before I get lynched I should quickly point out that UK Volvo owners nowadays are a totally different breed, we even use 155mph T5's as police motorway patrol cars, not much escapes them, oh yes, we're a sexy bunch now!

I'm glad you're smiling Tim, I was getting a bit concerned for you mental wellbeing for a while!

Had a look at the uTube but I can't imagine UK Volvo owners being too interested in Lattes or Sushi, I think they tend more towards vegetarianism nowadays, going back 20/30 yrs to the 2's and 7's you could always recognise the Volvo owner as he [never a she] always had a hat on [not a flat one] and probably a pipe on the go with a very thick outdoor coat on. They were just about the most dangerous people on the road, I think the theory was it was a safe car so I'll do what I like in it!

Volvos, like a lot of European cars must have come as a bit of a culture shock to some people in the USA all those years ago, you know, safe, go round corners, stop ok, rubber tyres, reasonable economy, etc. The latest Volvo TV advertisement over here describes them as "Sexy", they're looking for a new image!

Have a good weekend, I'll post the outcome when I've got my shaft cleaned and greased.

Regards, Bob.

No apology necessary. "Family newsgroup, buddy" is a standard Usenet joke tossed out in response to a double entendre, not an indicator of actual disapprobation. Perhaps I should have included a ;-)

LOL! Much there same here in the US. Volvos- especially the 240-740 models- have two images here: one of stodginess and the other of left wing liberal politics. They are stereotypically seen here as being driven by college professors and old men wearing hats, especially by the nattering nabobs of negativity that infest the American right wing of politics.

It was summed up neatly here:

I don't know about the UK's political process, but this is representative of the typical level of political discourse in America. I think it explains a lot about the last 30 years.

Cheers!

You know us Yanks, we're always crabby about something. ;-)

LOL! Here in Minnesota (where there are lots of folks of Scandinavian ancestry) there are a *lot* of Volvos. In Minneapolis it's hard to go a city block without seeing a 240.

Here too, both Saab and Volvo were trying to smarten up their image for the younger set. What it seems they mainly achieved was more middle aged women driving newer Volvos and middle aged to elderly men driving older Volvos... in hats. Come to think of it, I drove my 240 while wearing a hat today. D'oh!

If I didn't have scheduling conflicts, this is where I'd be this weekend, having hauled our cycles to the start via the wife's 240 estate car:

We even have a few ex-pat Englishfolk who turn up for this. Today they needed their capes and spats to be sure, and the roadside brew-up would have been a challenge.

Well I think with that level of Crabbiness you ought to be an honorary Brit!

Over here we can buy the ex Police cars, three years old, 100k miles, mega service history, all motorway miles, 70 series T5 150mph estate cars for about £4000 or say $5000+ [forecourt price twice that], all converted back to standard interior and exterior. I "really" want one, only put off by that fact the insurance is 3 or 4 times my old 760 Estate.

Three speed rear hubs, Sturmey Archer? I didn't realize you USA'ers did that sort of thing, mind you that rear hub might well be American origin?

We don't have that many 240's left here I think the wet and rust has got to them. I drove large Ford estates for years, wish I'd discovered the 7 series a while ago! No rust, much safer. Now where's my hat and pipe gone?

Bob.

You know us Yanks, we're always crabby about something. ;-)

LOL! Here in Minnesota (where there are lots of folks of Scandinavian ancestry) there are a *lot* of Volvos. In Minneapolis it's hard to go a city block without seeing a 240.

Here too, both Saab and Volvo were trying to smarten up their image for the younger set. What it seems they mainly achieved was more middle aged women driving newer Volvos and middle aged to elderly men driving older Volvos... in hats. Come to think of it, I drove my 240 while wearing a hat today. D'oh!

If I didn't have scheduling conflicts, this is where I'd be this weekend, having hauled our cycles to the start via the wife's 240 estate car:

We even have a few ex-pat Englishfolk who turn up for this. Today they needed their capes and spats to be sure, and the roadside brew-up would have been a challenge.

That sound very nice indeed a T5 with history s 70 here is $$$and more than

3 years old for sure . We in Australia don't as a rule have rust issues .Besides a drought for the last ten years means dry cars . Now the drought has broken thank good ness the GM and Ford cars will rust as usual . My 740 1990 21 years old turbo has no rust and it's undercover but not garaged . Being black maybe helps as it's a warm car is any sunlight . Oh we don't have salt problems here either . Cheers

I see I have just received my reward for posting on this "family" group, a nice batch of 30+ spam emails offering to sell me almost any service I would like from a degree to a book writing course to say nothing of the Asian singles desperat to get in touch! What a shame, pity there's not an easy way to stop this address harvesting. Do people really respond?? Will he investigate the push rod today ................ maybe!!!! Bob.

Enough do to make it worth doing. If you send out 20 million spam e-mails and 1% respond and surrender their credit card information, you've got a lot of credit cards.

I get very little spam but my ISP has user-configurable server side spam filtering and my mail application has good Bayesian filtering and easily configured rules.

Well I've finally dismantled the push rod and it's like new, put a spot of grease on the shaft and where the plunger goes into the master cylinder but it seems to have made no difference other than a slightly firmer starting push to the pedal [which could well all be imagination], it will still sink down a bit as before on a reasonable speed hardish stop!

Any thoughts on these please:

I can't see it's the booster, surely it only adds power to the pedal push, if it was faulty would the pedal not just feel harder and need pushing harder? [Is there a diagram of the booster available anywhere or is it just a diaphragm with a solid push rod on both sides?]

I am leaning towards the master cylinder with "borderline" rubber seals that are ok until you make them work hard for a living, the added push from the booster then being just enough to overcome them but with the engine off [and no boost assistance] you cannot push hard enough to cause the slight amount of blow by you get with the booster. I tried driving a few yards with the booster vacuum blocked off and it was almost impossible to get the brakes to work at all [although the pedal felt high and solid], showing what a massive amount of push the booster adds!

If it was bad fluid surely in would be the same all the time? If it was wheel components surely it would be the same all the time? It's been like this but not quite as bad for a year or two!

Any > I see I have just received my reward for posting on this "family"

Enough do to make it worth doing. If you send out 20 million spam e-mails and 1% respond and surrender their credit card information, you've got a lot of credit cards.

I get very little spam but my ISP has user-configurable server side spam filtering and my mail application has good Bayesian filtering and easily configured rules.

But did you think it was the actual cure for "your" soft pedal? I would love some comments on exactly how the booster works as I was brought up in a world of "servos" that had fluid in them/could leak/fill up, etc, if I remember correctly? Bob.

I have a couple of thoughts.

The first is to consider bleeding the brakes to make sure there's no air- which is more compressible than brake fluid- in the brake system. This is the simple and cheapest thing to do. If the car pulls to one side when braking, I'd particularly suspect air in the front brake line for the side it pulls away from (e.g., if it pulls to the right, pay extra attention to the brake lines on the left).

The second is to examine the brake booster and vacuum system for leaks. The diaphragm in the booster could be shot, the booster shell could have a leak, there could be a leak in one of the vacuum hoses. The booster uses vacuum to assist the brake pedal and reduce the driver's effort needed to stop the car, but if there's a leak the assist level drops and the pedal continually sinks to the end of its travel. Vacuum hoses are cheap, brake boosters are not.

I "believe" all the wheel end bits are ok and working in a straight line.

As I mentioned before I have unhooked the vacuum hose from the booster, sealed up the ends and got a solid pedal [but with no assistance] which should to my way of thinking be the same thing as having a leak in the pipes? [ie: ambient pressure inside the booster, I heard air rush in when the hose came off], are you sure the pedal would go down to the floor and, ............. why, as I thought the push rod goes solidly through it?

Perhaps I'll bleed it all through next week and see what happens?

Regards Bob.

I have a couple of thoughts.

The first is to consider bleeding the brakes to make sure there's no air- which is more compressible than brake fluid- in the brake system. This is the simple and cheapest thing to do. If the car pulls to one side when braking, I'd particularly suspect air in the front brake line for the side it pulls away from (e.g., if it pulls to the right, pay extra attention to the brake lines on the left).

The second is to examine the brake booster and vacuum system for leaks. The diaphragm in the booster could be shot, the booster shell could have a leak, there could be a leak in one of the vacuum hoses. The booster uses vacuum to assist the brake pedal and reduce the driver's effort needed to stop the car, but if there's a leak the assist level drops and the pedal continually sinks to the end of its travel. Vacuum hoses are cheap, brake boosters are not.