Car troubles

[Gizmo]

Actually, troubles with two different cars.

First, my mother's minivan - 1994 Plymouth Grand Voyager

The brake pedal goes all the way to the floor, and only the driver's side front wheel seems to be working well. The master cylinder had been allowed to run low on fluid, and I thought that it might have pumped air into the lines, so I tried to bleed the brakes. Couldn't get at the bleeder valve for the passenger rear, but bleeding the brakes had ZERO effect, so I figured that the master cylinder had gone bad.

Replaced the master cylinder, same problem. Finally jacked up the rear of the van so I could get at the bleeder valve on the passenger rear wheel. Once that was done, brakes worked great. Just to be sure, I went ahead and bled the rest of the brakes. Wouldn't you know it? Brake pedal went all the way to the floor again. Bled the passenger rear ONLY, and brakes worked great. So, I figured the problem was fixed; drove the van around a bit, brakes worked. Parked it for about an hour, came out, nearly had a wreck because I was back to the driver front wheel being the only thing stopping me.

Could the proportioning valve have died on me? In 25 years of messing with cars, I've never seen one fail, but it's the only thing left. Trouble is, it is a dealership only item (meaning $$$$) or I have to find one at an auto salvage and hope it works.

BTW, I've traced the brake line, and I see no evidence of leaking brake fluid anywhere.



Second problem - 1996 Ford Mustang
The speedometer became intermittent last fall, and quit working altogether sometime around late November. It has been pretty much not working since then, until this past week when the temperature got warm again. Up until today, it has been working just fine, until the temp dropped today and now it is going intermittent.

These things are electronic, but has anyone seen anything like this before? Is the sensor inside the transmission, where I have to drop and disassembe the whole darned thing to fix it, or is it mounted somewhere that I can replace it fairly easily?

[robbie]

The cable that comes out of the transmission that leads to the speedometer has a tendency to have the gear on it go bad.

As far as the brakes go, when bleeding them start with the LONGEST line first (usually right rear) bleed it until it pumps clear and then move over to the left rear, rinse and repeat. Front right, then left. Be sure the calipers in the front move free and smooth.

[Gizmo]

Originally Posted by robbie

The cable that comes out of the transmission that leads to the speedometer has a tendency to have the gear on it go bad.

Yeah, I've had problems with those before. However, I was under the impression that vehicles made since the early-to-mid 90s that used an electronic speedometer used a hall-effect sensor inside the transmission to pick up the drive-shaft speed.

A mechanical cable attached to an optocoupler arrangement (similar to mechanical mice) would certainly explain the symptoms I'm seeing, though.

Originally Posted by robbie

As far as the brakes go, when bleeding them start with the LONGEST line first (usually right rear) bleed it until it pumps clear and then move over to the left rear, rinse and repeat. Front right, then left. Be sure the calipers in the front move free and smooth.

Um........yeah. I've bled my fair share of brakes.

What you describe is good for rear-wheel drive, however generally with front-wheel drive you bleed passenger rear followed by driver front, driver rear, passenger front, because of the way the proportioning valve operates on front-wheel drive. The Chilton's manual also recommends this pattern for the minivan.

It's definitely got me scratching my head, but I really don't see how it could be anything besides the proportioning valve. I can't see any evidence of a leak, and anything else (like a bad wheel cylinder or caliper) wouldn't cause it to behave like this. I also know the master cylinder is good because I bench-bled it when I put it in the van. Besides, it's not like the brake system contains that many parts to fail.

[robbie]

Slaps forehead... Oh I forgot... check the front brake lines. Do they have a wire wrapped around them? I had a set that would expand after they got warm. Wrecked havoc on the brakes.

[keithwalton]

Are the brakes a dual circuit system (most modern vehicles are) if so whats the split, for safety it should be front near side and rear offside paired together and front off, rear near as the other pair rather than front to rear split, or near to offside split.

You should bleed the pairs together with as said longest of the all first then its pair.

What are the brake lines made of steel or copper alloy ? either way they could be on there way out.

Are they disc or drum brakes ? sounds more like a sticking caliper to me though that would be more like loosing 1 brake not 3.

Interesting that my car decided to drop a load of lhm earlier (runs brakes, suspension and power steering) i had topped it up a month or so ago as i thought i was low. I lowered the car for the first time in a while (you need to exercise it every now and then) and it decided to drop a load of the stuff

[Gizmo]

Originally Posted by keithwalton

Are the brakes a dual circuit system (most modern vehicles are) if so whats the split, for safety it should be front near side and rear offside paired together and front off, rear near as the other pair rather than front to rear split, or near to offside split.

You should bleed the pairs together with as said longest of the all first then its pair.

Yep, that's exactly what I did. It's dual circuit, opposite side split.

Originally Posted by keithwalton

What are the brake lines made of steel or copper alloy ? either way they could be on there way out.

Steel. However, like I said, I've traced the brake lines and haven't seen any evidence of a leak.

Originally Posted by keithwalton

Are they disc or drum brakes ? sounds more like a sticking caliper to me though that would be more like loosing 1 brake not 3.

Front disc, rear drum. I've never seen a sticking caliper cause the pedal to go all the way to the floor, though. And I can't pump the brakes up, either, the way you can if the problem is due to air in the lines or something like that.

[keithwalton]

Sounds like the fluid is going somewhere but where ...
Are the front calipers auto adjusting for pad wear ? i wonder if after a few pushes the front nearside pads end up sitting to far away from the disc to make contact, like if the auto adjuster is working the wrong way each time you stop. Not sure how bleeding them temp fixes it tho.

Are they servo assisted ?

It would make sense that its the front thats the problem as the bias is probably 60:40 (F:R) or there abouts.

[cloasters]

Cars that don't move or stop correctly are the worst albatross of all. Argh! Sorry that this Plymouth van(run for the hills, Dodge vans aren't good, AFAIK!)is giving you so much lip.

[Gizmo]

@cloasters: Knock on wood, but this van has actually been pretty good to me over the years that I've owned it. This is the first major problem I've had with it in almost 8 years.

@keithwalton: Every disc brake I've ever seen was inherently self-adjusting, because the pad 'floats' just above the disc until you step on the brake; it's the nature of the system. The auto-adjusters on the rear drum brakes appear to be working fine, and the pads are adjusted properly (near as I can tell without actually pulling the wheel).

No, the brakes are not servo-assisted; no ABS or any of that stuff.

[Daniel ~]

Find the fluid, find the leak... it has to be a leak right?

[Gizmo]

Originally Posted by Daniel ~

Find the fluid, find the leak... it has to be a leak right?

Well, one would think so, but I have seen no evidence of a leak. I've traced all of the brake lines; no sign of fluid anywhere.

[Gizmo]

Well, I went to the auto salvage and got a proportioning valve off an '89 Dodge Caravan (same chassis as my '94 Voyager), installed it, and everything seems to be working.

[Daniel ~]

So what happened to the missing brake fluid...sorry but I'd hate to see it show up to bite you in the ass!

[Gizmo]

Originally?

Dunno. It hadn't been checked in a thousand years, so there could have been a very slow leak in one of the seals or something. It isn't a bad enough leak to be obvious; at least not yet.

[Daniel ~]

Cool, I envisioned a some what more dramatic situation with quantises of brake fluid vanishing":O}