YAKES!! no brakes

[GatorBate]

One of the first parts to go south on my jeep was the vacuum boost on the brakes. The diaphragm tore. So, I go the the web and find the best deal (cheapest) i can . I got what I paid for I think. I really cannot lock up the tires when I'm on a steep slop and now that it has been below zero around here for a while I have to really stand on the petal to stop it until it warms up.

So I think I need a better vacuum boost and make sure that I have the correct master cylinder. I have the stock disk on front and drums on back.

What is a good upgrade for the vacuum boost and master cylinder?

 

[tarry99]

One of the first parts to go south on my jeep was the vacuum boost on the brakes. The diaphragm tore. So, I go the the web and find the best deal (cheapest) i can . I got what I paid for I think. I really cannot lock up the tires when I'm on a steep slop and now that it has been below zero around here for a while I have to really stand on the petal to stop it until it warms up.

So I think I need a better vacuum boost and make sure that I have the correct master cylinder. I have the stock disk on front and drums on back.

What is a good upgrade for the vacuum boost and master cylinder?

First off check your vacuum.........should be at least a "Minimum" 17 inches. 20 is better .........if your at altitude a double 8" Diapham is what I would use if you have the room. Any of the aftermarket ones should be fine as there all approved. There should be a Proportioning valve ( Disc. to Drum ) somewhere in your system.........and hopefully you do have the correct Master Cylinder.........hard to tell from the outside, the bore size is the difference.

 

[Torxhead]

I have heard Parts Mike @ 4x4 upgrades and parts for Jeep, Toyota, Broncos Scout trucks - Categories has a bolt on booster that is pretty good. The YJ booster is a popular add on, but the brake lines are on the oppisite side. I also have the stock brakes on my '86, but it sees little street driving, off-road it is just fine. I was suprised by the results when I replaced the oem prop valve with a Crown version so I guess they wear out also, plus eventually get filled up with .

 

[Tinman22]

I've been waiting two days, can't take it any more, where do the Yak's come into the story! I hit one of dads cows even with brakes we still laugh today!

 

[thiswontbetooexpensive]

I've been waiting two days, can't take it any more, where do the Yak's come into the story! I hit one of dads cows even with brakes we still laugh today!

I bet that the spell check got the original poster on this one!

 

[GatorBate]

Re: YIKES!! no brakes

@#$ New smart phone, small print, deteriorating eye sight, Oh heck, that one just got by me. However, Tinman22 there is a guy that lives up the canyon pass the lake in the middle of some great slick rock that owns a herd of Yaks. I'm sure I could come up with some sort of a story this summer (There's been a time or two I REALLY wanted to try out my bumper on a few cows around here too. But they have to be able to walk into the slaughter house under their own power, so i restrain myself)

Terry, a few months ago I found a broken rubber cap on a vacuum port. maybe I have another one, a cracked cap might explain why the brakes are so stiff in the morning before the engine warms up. I think I will see about getting a new Proportioning valve on its way to. Replacing the 32 year old one couldn't hurt and it makes sense, that could be why I can't really stop my front wheels without standing on the brake petal.

 

[GatorBate]

Re: YIKES!! no brakes

Finely got around to measuring the vacuum. At operating temp its about 12 and when its cold (-10 or colder) its about 9 until it warms up.

I checked for vacuum leaks and could not find any.

 

[tarry99]

Re: YIKES!! no brakes

Finely got around to measuring the vacuum. At operating temp its about 12 and when its cold (-10 or colder) its about 9 until it warms up.

I checked for vacuum leaks and could not find any.

Gator..............9-12 inches of vacuum will not cut it..............As I said before a Minimum of 17 inches is required.......Did you put a new camshaft in this motor with more duration?......
Perhaps you need to take every line off of everything that is attached to Vacuum and check for leaks one line at a time.........I would do this without the motor running. Use a hand Vacuum pump to check each line ...........must be a large leak somewhere?????????????If not they do sell auxiliary vacuum pumps that run off of 12 volts but I do believe they also require a seperate tank.

 

[GatorBate]

Re: YIKES!! no brakes

I've not change the cam. I don't know if a PO changed it or not. The only vacuum line connected to the engine is the vacuum boost for the brakes. I plug that line and it did not change the vacuum any. What else effects your vacuum besides a cam. burnt valves, worn rings

 

[tarry99]

Re: YIKES!! no brakes

I've not change the cam. I don't know if a PO changed it or not. The only vacuum line connected to the engine is the vacuum boost for the brakes. I plug that line and it did not change the vacuum any. What else effects your vacuum besides a cam. burnt valves, worn rings

Yep............all of the above.......I would do a compression test & a leakdown check on all the cylinders.
Does the motor run oK?
Anything along the intake track..........gaskets at the manifold, gaskets under the carb.......is there any plugged ports in the Carb or carb base that are leaking or missing?

 

[GatorBate]

Re: YIKES!! no brakes

Well, that was depressing. I finely had the time to warmed up the jeep and run a compression check... 125 on #1 and 90 to 105 on all the rest. It runs OK, just not a lot of power on the top end.

Terry99, how do you do a leakdown check and what does it tell you?

 

[tarry99]

Re: YIKES!! no brakes

Well, that was depressing. I finely had the time to warmed up the jeep and run a compression check... 125 on #1 and 90 to 105 on all the rest. It runs OK, just not a lot of power on the top end.

Terry99, how do you do a leakdown check and what does it tell you?

Gator, First off doing a compression test is OK but only relative to the person administrating the test IE; engine warm all plugs out and a specific amount of cranking over equal on all cylinders........having said that results can vary.

Leak down.........warm engine , plugs out and whatever cylinder should be at TDC ( Top dead center) or at least a few degrees from that point, you want the piston up whereby it would be sealing the compression stroke.
The leak down guage needs a compressor to give a specified amount of air pressure to load one half of the guage.....via the regulator (see the picture) the other line is screwed into the cylinder......the guage will now tell you what the percentage of leak as compared to the line pressure you have............while the air pressure is on you can also open the blade on the Carbureator and if you hear hissing that may tell you and intake valve is leaking same goes if you can hear hissing at the exhaust.......or if you take off a breather vent and hear hissing the rings could be allowing air to be bypassed to the crankcase. It is also a good Idea to have a breaker bar and socket handy not only to get the piston on TDC but to move the crank a few degrees either direction to seat and unseat the rings........

Keep in mind this air pressure is filling the cylinder with air so do check for leaks at the head and manifold gskts also......and pull the radiator cap and look for bubles also............this is a more complete check of the system........there are cheap guages at Harbor Freight or better ones at Summit or Jegs.........if you have a mechanic or hot rodder in the neighborhood.........maybe he already has the guage and will give you a hand..........write everything down and keep your air pressure consistent throughout the test............Good Luck!