Two Mechanic Questions - old chevy truck and 8n

NewEnglandFarmer · Oct 22, 2009

I have two questions

First.. 1985 chevy pickup. The parking brake light in the dash is staying on. I know there cant be a sensor in a vehicle of that age, any suggestions? Also too, the brake pedal goes down quite a ways, you would think its low on brake fluid but its not, any suggestions?

Second.. Ford 8N tractor. a new puddle of oil coming from the motor. the govenor, behind the generator, is soaked, so is the side of the block/oil pan behind the govenor. didn"t look at it that close. any suggestions?

BCnT · Oct 22, 2009

first on the truck...chances are master cylinder is bypassing between chanbers...that "sensor" has been on most vehicles since mid 60's when dual master cylinders were introduced...it shows pressure difference between front and rear brakes.

off top of my head i'd look at lifter gallery gaskets first on the N...covers could have worked loose too.

landlord7012 · Oct 22, 2009

You must be pretty young to call an '85 "old" but maybe that's just me...as for sensors - they had plenty of them even in 85. The sensor you refer to is a simple pressure sensor that monitored a minimum line pressure or presence of fluid. You likely need to replace the master cylinder.

Good luck,
Bill

Old Ford Mechanic · Oct 22, 2009

First the truck.Check the brake lining's on the rear.If they are worn out replace them.If they still look good adjust them tight then back off enough for the wheel to roll without friction.Do both sides and the light should go off.As for the tractor i would suspect the front crankshaft seal or a leak at the govonor arm.A tip now;I would inspect the brake shoe adjusters also.They may be seized up and not letting the self adjusters work.

Bob85355 · Oct 22, 2009

Assuming you meant it when you said truck parking brake, look for a pressure push type switch in your parking brake pedal linkage. Its either gone bad or is stuck. On the low brake pedal, if your master cylinder is full and your pedal is low, you probably need to adjust your brake shoes. You can do it by braking while in reverse and moving or pull the drums.

Bob

Anonymous-0 · Oct 22, 2009

on the truck ,,try lifting up on the parking brake pedal . They should have a switch there . sometimes pedal don't return all the way up and makes light come on . If not that ,check fluid, adjust brakes ,bleed system .

RodinNS · Oct 22, 2009

The tractor.... get a pressure washer out, or even better, a steam genny and clean it off. Just look for the source of the oil.

The truck... I would suspect a busted rear brake line. It may be a low fluid sensor too. I dunno... but most times I find it's a busted line. Crawl under and have a look. Being an '85 it'd be due for about it's fourth set of lines around here by now.

Rod

shaun wallace · Oct 22, 2009

On 8N sounds like govner hsg has hole beat in it from govner balls. On truck look at other posters suggestions.

axhandle · Oct 22, 2009

what lite is on the brake lite or parking brake lite two differnt problems ones would be the park brake switch and the other one would be on the switching valve to see if your masterclynder is bad push on your brake padle and hold down if it keep going down and dont stop your master clynder is bad if it stop check your rear brakes you proble will have to bleed them

axhandle · Oct 22, 2009

what lite is on the brake lite or parking brake lite two differnt problems ones would be the park brake switch and the other one would be on the switching valve to see if your masterclynder is bad push on your brake padle and hold down if it keep going down and dont stop your master clynder is bad if it stop check your rear brakes you proble will have to bleed them

old · Oct 22, 2009

There is in fact a sensor on the brake lines close to the master that will cause that problem. My 1980 has one so I know yours will also.
As for the 8N most likely the gov. housing is loose or the gasket there it going bad.
Yep I own both plus some. Shoot if I remember right my 1969 Chev had that also on the master

S.Crum · Oct 22, 2009

The sensor everyone is speaking of is mounted in the proportioning valve mounted on the frame below the master cylinder. This valve monitors the correct pressure between the higher pressure front disc brakes and the lower pressure rear drum brakes. Usually if the light is on due to a pressure problem it's because of a blown brake line which is more than likely on a truck of that vintage (rusted). All the lines should be replaced on the truck for the least amount of headaches (the ones that don't leak will, once you disturb them changing the one that blew). Once the system is in good order and the brakes bled correctly the valve re-centers and the light goes out. If the parking brake (same light) is at fault it's likely a stuck parking brake cable due to crud and rust. How's you gas mileage?

Anonymous-0 · Oct 22, 2009

The BRAKE warning light is connected to BOTH the parking brake AND the brake pressure differential switch on the firewall. The link below will tell you how the brake pressure differential switch works, and WHY you need to get your brakes checked out NOW.

It might save your life.
Brake Pressure Differential Switch

NewEnglandFarmer · Oct 23, 2009

Haha you're right, I may not be a young'n, but I'm sure I'm younger than most of the people on this website.

Even though the truck is an '85, it only has 58K on it, no rust underneath, never seen a winter. Entire brake system is original. Master cylander, brake lines, rear drums. I did do the front pads about 10 years ago, or 10K miles ago. Thanks for the tips

tlak · Oct 23, 2009

If it's like most Chevy trucks your brake line rusted through on the frame rail.

John M · Oct 23, 2009

1 master cylinder, I guess others didnt see the part where you werent losing fluid.

2 Probably a gasket somewhere.

Kentb of SWMO · Oct 23, 2009

I did not read all of the post but the master cylinder is by-passing fluid internally on one of the two half. This causes a pressure differential the is causing the sensor to set the light. Replace the master cylinder.

Kent

Sid · Oct 23, 2009

"I guess others didnt see the part where you werent losing fluid." You noticed that too huh. A least I know who ain't working on my brakes.

John M · Oct 23, 2009

Yep, I see alot of that on here, people ready with a solution without knowing the problem.

RodinNS · Oct 23, 2009

Ya might also know that it takes a while to drain the master too then. I don't know about you, but I notice pretty damn quick when I don't have back brakes... so the fact that the resevoir is not empty is meaningless to me. It's just not empty YET.
I dealt with this very same problem on a '97 GMC 3500 about 2 weeks ago. It never emptied the resevoir but it had a very busted brake line along the frame above the rear axle.

Mabey this fellow does have a bad master cylinder. I dunno... but the first LOGICAL place to look on a 25 year old truck is a busted line.. then if you eliminate that probability you continue on to more expensive problems like master cylinders. This, unless you prefer to spend 1-200 bucks on a master cylinder based on a whim and a prayer that it might fix the problem?

Rod

John M · Oct 23, 2009

One would think that if theres a leak, it would show up as a low level in the MS. The one you worked on may not have been empty, but Ill bet it was low!

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