TN75da brake issue

[elkhurst1]

Hello all, been a while since I've posted and have questionable brake issues. I definitely need some expert advise!
A little long winded, so bare with me....
Back about 6 weeks ago, I had to roll my TN75da out of my heated shop to remove a tree from the main road at the foot of my driveway. I hadn't used the machine since late fall of last year. Traveling down my driveway I needed to downshift, so I hit the clutch and brake and both brake peddles (pinned together) went nearly to the floor! It did stop so I continued on to finish what needed done trying not to use the brakes. I got the tractor back to the shop and the next day, my helper and I added brake fluid and tried bleeding both sides. The left was no problem, 2 or 3 times and what little air it had was gone. The right doesn't seem to want to bleed out after several try's.
While bleeding the right side, (like an idiot), I wasn't catching the fluid and started running short, so I had to stop while it still had some air and ordered more from my dealer. At that point, (for some reason), I decided to measure the amount of oil in the reservoir with a set of calipers and by the time I got new brake fluid, (7-10 day's later), the oil level had dropped about .050", so we bled both sides again. The left side had no air, the right still had air, (and seemed like more). After bleeding the right several times, the air never did go completely away. At that point I tried pumping each individual brake as if you were running the machine to see if the oil level dropped in the reservoir wondering if I might have a brake pack bypassing under pressure. After about 75 pumps each, no oil level drop. I wound up getting busy on other things and came back to it about 10 day's later and it had lost another .050" of oil from the reservoir in which the tractor hadn't been started or moved out of the shop. We bled both sides again and the left still had no air and the right had air. We did the complete routine again Friday after the reservoir dropping another .040" in 7 days, and again, we still weren't able to get all the air out of the right side.
There are no apparent oil leaks in the complete brake circuit, and both pumps were replaced appx. 5-6 years ago with no leakage on either of those.
The tractor has just over 3000 hrs. on it.

The oil is going somewhere and creating air, is the right brake pack leaking internally under (no) pressure?

Gary

 

[TractorTech]

Most likely the brake piston in the rear end is leaking into the axle as you have stated there are no external leaks. You could measure the oil on the dipstick for the rear end/hydraulics, but you have pretty much ruled out anything else.

 

[LouNY]

I didn't look up the parts breakdown on your tractor, but if it's similar to many NH's it has a balance line between the two master cylinders. When I got my 8160 I knew that the wrong fluid had been used in the brakes do i flushed it quite well and still ended up replacing both master cylinders. I could not get that system well bled. It was kind of a nightmare I even reverse bled the system going through 3 quarts of that expensive mineral oil. If you pushed both pedals at the same time you would think that you were doing great, you could bleed each side separate and one side would feel good and the other would be spongy. If you double pumped the brakes she'd skid either tire. When you would push both pedals half way down then press harder on either one you could pump them like bicycle pedals, one down the other up and you could do that for as long as you wanted.
Until I removed and plugged the crossover line I could not get good brakes on her. Removed the balance line and plugged the ports and both brakes are working great.
Which is a good thing as replacing the seals on those brakes is an involved job.

 

[Tractor2Big4Me]

Reviving an old thread again, but I am having the same problem with my TN65. I had to replace a master cylinder last summer because it started leaking where the push rod entered the master cylinder (the tractor had not been used much over its life). I replaced the master cylinders with the FridayParts version (https://www.fridayparts.com/brake-m...-tn70a-tn75a-tn60va-tn70va-tn85a-tn70na-tn95a) because the OEM master cylinders are over $500 each. After some initial bleeding trouble (my fault), I got a solid pedal on both sides. However, just like LouNY said above, if you push both pedals and happen to press harder on one of them, they both sink to the bottom. To reset them, you have to push really hard on one side and you can feel something like a "click" in the pedal (like an internal valve has been reset), then they work normally again (until you press harder on one side). I have used almost two quarts of the "unicorn blood" mineral brake fluid trying to get them bled. I have power bled and manually bled them (with a helper at the pedals). There is no obvious fluid loss and the pedal for each side is individually hard as a rock.

I haven't gotten to the point of removing the crossover pipe yet, but I have thought about it. I have read the owner's manual and repair manual sections on bleeding the brakes and both say to bleed them the traditional (pedal pushing) method until no air is visible. I have done that repeatedly.

Is there some air trapped in the crossover section that needs to be "burped" somehow? Is there some trick for bleeding this system that is only known to a few people? Are the FridayParts parts just junk? If so, is there a rebuild kit available for the OEM parts (I kept mine). I have been bleeding brakes since I was a kid helping my grandfather (a mechanic), so I feel like I should be able to handle this. It is driving me slightly crazy. Any suggestions would be appreciated!

 

[LouNY]

I had to remove the cross over line on my master cylinders and have had no issues since. I think what is happening is the balance ports or seals are just a bit out of spec compared to the OEM master cylinders. But at the price of the OEM masters and having excellent brakes with out the balance line, I'm running without it.

 

[Tractor2Big4Me]

I was wondering if there is air trapped in the crossover system that needs to be released. I didn't see any instructions for bleeding the crossover system and I thought I would see if anyone had advice before plugging the system. I am really curious to see if this is related to the aftermarket parts--if so, they really need to update the design.

 

[elkhurst1]

I believe I finally got my brake issues taken care of about 10 days ago.
Turns out both of my brake pistons were leaking into the transmission.
Back in April I pulled the right side axle and replaced seals and springs in the piston which really wasn’t a terrible job. Afterwards I monitored the brake oil level in the reservoir for a few weeks and it still continued to drop at about 1/2 the rate it was before.
It seemed like when I ran the tractor and got the oil heated up, the oil level wouldn’t drop for a few days when the tractor was sitting. I guess the heat expanded the seals to temporarily seal everything up??
I waited to do the left side after I got my hay put up. There was a little more to it since the fuel tank had to come off, but as of now, the oil level is staying put and the brakes work great!
I have a TN55 as well and thinking I should rebuild both pistons on it too??

 

[Tractor2Big4Me]

Latest update to my brake saga.

My latest FridayParts master cylinder (on the left side brake) seemed to bind up near the end of the throw right out of the box. It worked for about six weeks and then it wouldn't hold pressure or allow me to bleed it anymore. Instead of pumping fluid to the wheel, the unicorn blood fluid spurts out of the brake fluid reservoir and the pedal goes all the way down with little resistance. Clearly, the brake fluid is bypassing the internal piston in the master cylinder. They sent me another one under warranty and I'm about to go through the exercise of putting it on the tractor. I'm tempted to buy plugs to seal off the crossover port, but they seem to be M12x1.25 threads. There is no way that I am going to find a plug or short enough bolt like that locally. I would need about a 3/4" length bolt or actual plugs. The shortest bolt I could find locally was about an inch.

My original right FridayParts master cylinder still works unless you press the left brake pedal at the same time--in that case, the pressure from the right side seems to go to the left side and the right pedal sinks.

I'm getting a little scared of the FridayParts units. I have bought three of them and two of them failed pretty quickly. I blamed myself for the first failure because I thought maybe I bled it wrong, so I bought the replacement part instead of asking for a warranty replacement. I'm positive I did the next one properly and, like I said, it tended to bind near the lower end of the pedal throw. I really have to wonder if the crossover design is just wrong on the FridayParts units--it seems like they work until you feel a "click" in the pedal, and then maybe the crossover activates? I was able to feel the pressure from the right side pedal on my failing left side pedal until it completely gave out, so I know the crossover was doing something.

I still have one good OEM Bosch unit left--the inner one started leaking at the input seal, which started this whole drama. I have spent about $300 on FridayParts units so far, plus $75 in unicorn blood mineral oil brake fluid. I'm starting to wish I had just spent the $500 to get a new OEM unit.

Does anyone have a decent source for used New Holland TNxx parts or know of anyone who sells OEM parts at a decent price? I'm getting tired of swapping units...

 

[Tractor2Big4Me]

Hopefully, this is the last installment of my brake saga. I hope it helps someone else someday.

As I mentioned in the last past, I have purchased three FridayParts master cylinders--one of the original two purchased (outboard location) still worked fine. The inner one would not hold pressure--it would work if you only pressed the left brake, but pressing the right brake pedal simultaneously made it sink to the bottom with no pressure. So I bought another master cylinder, thinking I may have damaged it during installation. The third new master cylinder (left side) worked for a while, but the piston seemed to bind up internally from time to time. This part eventually got to the point where it would no longer hold pressure at all--it seemed to just get stuck in the bore. I emailed FridayParts and they were really good about getting me a warranty replacement (delivered in 2-3 days).

I have determined after three iterations that it is not necessary to remove any external part to get the inner master cylinder off. Just remove the 17mm brake line hollow bolt, the lower crossover line (also 17mm), remove the pivot pin from the brake pedal, and use a ball stud hex socket to remove the studs holding the master cylinder onto the tractor. Remove the end from the push rod (loosen 14mm nut, then spin off the nut and pedal bracket). Remove the rubber boot, then push the master cylinder toward the middle of the tractor (there is a passage behind the engine). You will need to loosen and remove the supply line at some point--I was able to do that while wiggling the master cylinder around. If you are patient enough, you can get the master cylinder out by snaking it under the outboard master cylinder. Remember to find the copper washers that are located on the output and crossover lines--it's a good idea to get the assortment of copper washers from Harbor Freight before you begin this process. Hooking up the inboard supply line is a difficult task with the outboard master cylinder still in place, but it is possible if you have some patience and don't mind the sight of your own blood. I should also mention that a plastic cup is good to catch the mineral oil brake fluid that will be flowing freely during this operation.

I replaced the inboard master cylinder with the new FridayParts one. I went ahead and installed the crossover line and vacuum bled both sides. The new FridayParts master cylinder worked great, but the outboard master cylinder that HAD been working would no longer hold pressure, no matter how much bleeding I did. I tried removing the crossover line, installing plugs, and bleeding again. Still no pressure on the right side. The problem with the left brake had switched to the right brake now. In desperation, I yanked the original right FridayParts master cylinder (same technique as above) and replaced it with the one good remaining OEM master cylinder. I used the plugs instead of the crossover line and bled both sides again. This time, I had absolutely perfect brakes--rock hard. I did not try reinstalling the crossover line yet--I will leave that exercise for another day. I suspect the new FridayParts unit will fail shortly. When that happens, I will spend the $518 to buy an OEM part because my sanity is worth more than that and I have spent days replacing parts so far. I have also spent $400 on three FridayParts units and three quarts of mineral oil brake fluid. I wish I had just bought an OEM part to begin with. The FridayParts customer service is awesome, but I'm afraid this particular part is sketchy.

By the way, if you want to plug off your crossover line at any point in time, go to your local box auto parts store and buy a Dorman M12 x 1.25 mm oil drain plug--it is marked as being for a Nissan (get the stubby one--NOT the one with the extended magnetic tip). They are about $5 each and they plug the crossover port perfectly.

So, the moral of my sad story is this: Sometimes it is better to just spend a ton of money to get an OEM part unless your time is worth nothing and you enjoy spilling large amounts of expensive mineral oil brake fluid onto your shop floor.

 

[Linda White]

Has it been resolved? This is very important to me. I've heard that FridayParts is a reliable source for aftermarket tractor parts, my friends recommended it, so I've added it to my candidate list. I think... I will try one, maybe someday.