Hey all - new to the forum but I've been driving Ford trucks for close to 15 years.

Just bought a 1980 F700 with a 14-foot dump body. It's got a 370 4V, and 5-speed manual transmission with split rear.

The seller had someone replace a bunch of stuff on it - including most of the brake system. New master cylinder, new booster, new wheel cylinders and most of the brake lines are new.

But despite all those new components, he said they couldn't get the brakes to work right and his mechanic couldn't figure it out (I'm thinking he was using some shade-tree mechanic instead of a truly qualified truck mechanic). He was selling the truck anyhow, and he dropped the price for me to take it with the brake issue.

The pedal goes to the floor and is very spongy, like the system needs to be bled. If you pump it several times, it will finally get firm and the brakes do work - and actually work well. But then the pedal will sink again and you'll have to pump it up again.

Today we bled all four corners and got a bunch of air out, put a bunch of new fluid in, but after all that, it's still exactly the same - as if it still needs to be bled. It's like air is getting back into the system right after we bled it.

One thing I noticed is that when I press the brake pedal with the engine at idle (which is a little rough), the engine slows down and stumbles - so I'm wondering if that's just from the vacuum booster affecting it or an indication of something wrong with the vacuum booster - like brake fluid leaking through the booster back into the engine.

I've found a local mechanic who comes highly recommended - he seems confident it shouldn't be a big deal to make the brakes work right. I just need to get the truck over to his shop. In the meantime, I'm just trying to get some ideas as to what the issue might be.

I'm open to ideas and suggestions.

Thanks!

 

Check the brake adjustment. Sounds like the wheel cylinders are overextending, which could let air in I suppose.

 

So getting back to this old truck -

I took it over to a local truck mechanic who works on trucks and heavy equipment for a living. He bled a lot of air out, just like we did, and found the same results - the pedal would get firm, but then next time he came back, it would go to the floor again.

He adjusted all the brakes so they're all set correctly. He's gone through the system several times to make sure all the lines were tight and no leaks. He has consulted with some of his buddies, and the general consensus is that it's a bad master cylinder. So he's going to replace the master cylinder with the hope that that will fix it. I'm hoping that's it also, because otherwise, it's a mystery and the truck is not much use to me.

 

Is that the Lucas-Girling system? I had one of those brake systems in an '84 F-700. Worked good once you spent the money and time to get it working.

Anyway, would be interested in hearing further.

 

Haven't got a clue. Don't know much about these trucks, to be honest. I mean, I understand how engines and brakes and such works, but I'm not familiar with the specifics of this particular truck. It's a learn-as-I-go thing...

Maybe you can enlighten me as to the Lucas-Girling system? Is there something I should know about it?

It seems to be a pretty simple system, really - master cylinder on the firewall, just like any other car or truck I've seen; vacuum booster under the cab, beneath the driver's seat, which seems an odd location to me, but whatever... and then lines to each wheel cylinder.

Thanks!

 

Some time around 82'- 83'- 84' Ford's medium duty F600, F700,F800 with hydraulic Brakes went to this Hydraulic Lucas-Girling Brake setup, it has a yellow pull **** on the dash(like an air Brake system) to activate the Parking(Emergency) Brake system, this system use's a hydraulic pump to build pressure to activate the rear Parking Brakes. this system is very expensive to repair and rather troublesome from what I have been reading

I recently purchase a 83' F-700 without the Lucas-Girling setup, it has the Parking Brake lever next to the drivers left knee, which activates a drum brake setup on the back of the trans, much less complicated !

 

OK, cool - that means no, I do not have that system. Mine is just like yours - the parking brake is a lever down low on the left, with a cable to a band brake on the transmission output.

The mechanic had another thought - that whoever put the new cylinders on might have put them on wrong, with the bleeders in the wrong position. He's thinking he should be able to get it squared away by the end of the week - I hope...

 

Good that you don't have Lucas-Girling. They are expensive. Hope the reversed wheel cylinders works out for ya!

 

OK, my mechanic figured out the brake issue. Turns out the master cylinder was bad and one of the rear wheel cylinders was leaking. A new master cylinder and wheel cylinder seems to have fixed the spongy brake issue.

Now I'm trying to make the parking brake work. The cable is totally seized.

So where the hell does one get a parking brake cable for a 1980 F700?? I've been searching the interwebz with no luck.

 

Mid Tenn Ford may still be able to get one . They are in Nashville . Just a guess !

 

Well a lot has transpired since I last posted. Figured I should get back and at least keep myself honest here.

The guy I had taken the truck to turned out to be pretty much useless. It became clear my truck was not a priority to him, and he wasn't doing anything on it, and in fact, he was pretty much guessing. It was just sitting on his lot, so I finally decided to just go pick it up.

Turns out his "helper" had moved the truck around the lot and left the key on, so the battery had died. He then went to jump start it, and hooked up the cables backwards and realized it when he saw smoke coming out of the voltage regulator. So when we got there to take the truck back, it was deader than a doornail.

The gas tank was also empty.

So we borrowed a gas can and put 5 gallons in, then jumped it and got it running, but it wouldn't stay running. Jumped it about 5 more times and I kept feathering the gas to keep it running. Drove off the lot and got about 1 mile down the road when it sputtered and died and that was all she had.

We sat there for over an hour, directing traffic around the dead truck, until the tow truck came. Not a fun day.

I determined that the guy had cooked the battery and the voltage regulator when he hooked up the jumper cables backwards. So I bought a new, heavy-duty battery and a new voltage regulator, and then it would run.

So I then took it to a much, much better outfit, that really knows old trucks and specializes in brakes, but they can do really anything on these old trucks.

I ended up spending - are you sitting down?

I had to spend... no, really, you should sit down.

$5,000.

So it turned out the truck needed much more than I had anticipated - but I'm willing to make the investment, because it's a good, solid truck overall - I'm just fixing all the neglect of the previous owners.

They had to basically rebuild the whole brake system. One problem was there wasn't enough vacuum to give you the assist needed, so they installed a vacuum reserve tank. They found all of the rear brake cylinders were leaking, so they all got replaced. Plus all of the brakes were not adjusted right at all, and all the shoes were totally worn, so they had to completely re-line and adjust all the brakes.

Then, to pass inspection, it needed a bunch more work.

They had to completely rebuild the parking brake - a new, custom-made cable (because you can't get that part anymore) and relined the brake.

New king-pins, bushings and tie rod ends.

Adjusted the clutch and steering box, both of which were sloppy and out of adjustment.

Rebuilt the shifting mechanism for the 2-speed rear axle - took it all apart, unstuck whatever was stuck, cleaned, lubed, ran a new wire and switch.

New plugs, wires, cap and rotor.

I picked it up and drove it back to my shop, and it seemed to work pretty well. Played with the 2-speed rear on the way and it works great.

A couple days later, I drove it to the gas station, since the tank was empty. Once I filled the tank, it would not start. Battery was stone dead. I got my friend to come give it a jump and managed to limp it back to my shop.

I figured the first idiot probably also cooked the alternator, so I pulled it out, and sure enough, it was shot. I figured while I was at it, I might as well replace the lock cylinder on the steering column, since the old one was broken - which is why the "helper" managed to leave it on in the first place. I also replaced the ignition switch, since the old one was pretty crunchy.

New alternator, ignition switch and lock cylinder: only $85. Now she starts strong and runs like a champ! Accelerates much better than ever.

But then I discovered it didn't want to idle. After much farting around with the carb, I discovered the intake manifold gasket is leaking. So I ordered a new one, which just arrived today.

So my task tomorrow is to replace the intake manifold gasket.

I think I'm also going to put a new distributor in there while I'm at it - it looks to me like the vacuum advance on the old one is stuck, which could contribute to the poor idle issue.

I'm getting closer and closer to fixing most of what could go wrong with this beast! And she's running better and better... the good news is that once I get all this squared away, I'm going to eventually make my money back with it.

 

I just passed out for a bit , 5 K !!!! I do not know what to say , how to respond to that . Well , if you are happy , truck is proper , Best of luck !

 

Yeah, it's a work truck, so once I get all the issues squared away, it will start making money for me. I'm still into it for less than $10K total, so I figure I'm doing ok. It's a brute, and I'm expecting it will continue to serve me for several years and I'll get my money out of it eventually.

 

They are good trucks , if properly maintained , And used sensibly ! I hope you have many years of use out of it . I have seen many beaten down from neglect and hard improperly maintained use .... Best of Luck !

 

I tell you what Bill, you tell a darn good story! I really enjoyed reading about your truck (not making fun of your misfortunes, but maybe making light of them), and can certainly understand your frustrations.

Doing the same thing with a '97 F-800 with air brakes. Fortunately I'm on the tail end of it (I think!) and I think I mighta made it thru. It was a lotta work from lights to brakes to windshields to electrical to mirrors to tarps to sideboards to tailgates to tires to cooling system to grease fittings to cab work to repainting to trailer hitches. But I might have a pretty good truck now.

You'll make it. Keep working at it.

And I was sitting down...good luck...Jim