Teves ABS Pump never stops

[DAVES89]

2seater as youknow I have 4 pumps waiting for your "Frankenstein" experiment. Tuesday afernoon , anytime Wednesday or anytime Friday works for me. Just let me know.

[2seater]

It seems odd that a check valve would have spring pressure holding it open. It seems like it should have spring pressure holding it on it's seat. Perhaps it is held open to allow air to easily escape when there is no pressure in the boost side of the system??

 

Agree a light spring for closure makes more sense, but it can definitely be moved slightly downward in the direction a check would tend to seat. I wonder if vacuum could be applied to the opening to assist if it is indeed slightly open? It would be nice if the pump could be rotated manually to assist with a bit more control but there is no way to do so.

[Ronnie]

Since the check valve is open it might be possible to pull a vacuum on the pump through the valve opening to get the air out. OR it might be possible to push fluid/air through the pump by applying slight pressure to the reservoir. However for either of them to be effective I think it would be best to remove the motor and slowly rotate the pump shaft manually while doing one of the above.

 

I'm thinking that allowing the pump motor to "spin" the pump quickly might be a source of cavitation that could cause the fluid & air to foam in the pump preventing it from passing through the pump passageways and out through the check valve opening.

 

I realize that all this is just talk on my part based on me looking at the photos and speculating on different scenarios - which might be way off base.  I don't have the opportunity to try any of this on my pump. (and I hope I never need to do it) :)

[2seater]

I took my mule pump apart some time ago to take the motor to a repair shop to see if it can be refreshed. It works but looks pretty shaggy on the outside. I broke the plastic inlet fitting on the '88 pump so I couldn't use that to test the vacuum theory but I will put one together to test the theory. I will make sure it is completely empty before trying it.

[2seater]

2seater as youknow I have 4 pumps waiting for your "Frankenstein" experiment. Tuesday afernoon , anytime Wednesday or anytime Friday works for me. Just let me know.

I am tied up this week so this week is not likely.

[2seater]

I did reassemble a pump and there is no joy on self bleeding from the non-return valve. I left it sit for 5 minutes and no fluid drop at all in the reservoir nor did the bubble in the clear fluid feed move at all. I then applied 25"Hg of vacuum to the check valve port and still no joy. No movement at all.

 

The only way I was able to get fluid to run into the pump was to hold the pump with the motor down at about 45* and rotated so the inlet nipple was pointed upwards slightly. That did reward me with a steady stream of bubbles out of the pump and into my fluid container. It took several minutes for the stream to stop and I then turned the assembly so the pump was straight down for 30seconds or so and returned to the 45* position with the nipple upwards. A few more bubbles appeared and that was about it. The amount of total fluid into the pump was 20ml. The accumulator does not need to be installed while doing this pump gyration as no fluid will run out of any port as it doesn't get by the non-return valve. I then tried the empty pump housing with the motor and screen removed facing straight up and the total fluid volume that filled that space was 25ml.

 

When bleeding the pump, I don't really know where the air goes, but I would believe some must be trapped in the accumulator so I would think it may be a good idea to charge the system fully and then deplete it completely at least once before putting in service.

[Ronnie]

Did you try turning the pump by hand to see if it made a difference in getting air out of the pump?

[2seater]

Did you try turning the pump by hand to see if it made a difference in getting air out of the pump?

 

That's the problem with the design. The motor is the wall opposite the pump, so the motor must be removed to turn the pump manually, The motor has a seal around the output shaft and a square ring on the end housing that seals against the pump chamber so the motor must be in place to form the inlet chamber for the pump. I am out of ideas on how to improve bleeding the pump. It really needs something like is done for bench bleeding a conventional master cylinder where curved tubes are installed in the outlet ports and directed back to the reservoir so the master can be cycled repeatedly.

[Ronnie]

 

That's the problem with the design. The motor is the wall opposite the pump, so the motor must be removed to turn the pump manually, The motor has a seal around the output shaft and a square ring on the end housing that seals against the pump chamber so the motor must be in place to form the inlet chamber for the pump. I am out of ideas on how to improve bleeding the pump. It really needs something like is done for bench bleeding a conventional master cylinder where curved tubes are installed in the outlet ports and directed back to the reservoir so the master can be cycled repeatedly.

 

I didn't know that. I've never seen one of them apart. I know by looking at the photo Henning provided that bleeding air out of a pump that has been drained was going to be a real problem.

 

We really need to come up with a procedure to bleed the air out of the pump in situations like this. I have a master cylinder, complete with pump, that I got from Dave. Dave had the forethought to cut and pinch off the brake lines when he removed it from the donor car to retain the fluid inside. I'm glad he did. Maybe I won't have to go through purging air from the pump if I have to use it on my car. But if I do, I would like to know how to get the air out

 

It seems like your twist and tilt method of getting the air out worked pretty well. Do you think enough air was out that the pump would pickup the fluid and continue to operate when installed on your car?

 

Thanks for the work you have done in trying to track down a good way to bleed the pump. Maybe it will help Henning get his brake problem solved. With your testing equipment and more discussion we might eventually find a good way to purge air from the pump. There has to be a way to do it consistently. The factory was able to do it.

 

WAIT. Would it be possible to fill the pump with fluid through the hole where the motor goes in until fluid runs out of the check valve hole and the fitting that connects to the reservoir hose and then put the motor back in place??? Naw, it couldn't be that easy could it?

[2seater]

It could certainly be prefilled with fluid while clamped in a vise and then install the motor although it would be very messy. You would need to plug the inlet fitting or much of it would run out. Of course if it is off the car, it could be filled through the normal inlet but it needs to be with the nipple pointed somewhat upward and the motor tilted down. Then repeat a couple of times. I should have taken a photo and I will do so when I have the chance and it will make more sense. When the assembly is in the mounted position, the fluid from the reservoir travels downwards and then back up into the inlet nipple, very similar to a P-trap under a sink. The fluid then runs into the pump housing horizontally until it intersects the other passage shown on the diagram where it turns straight down and enters the pump chamber vertically. That makes a sort of sense except at the inlet nipple end there is a nice air lock. To make matters worse, the opening for the pump to take in the fluid is near the bottom of the chamber with a nicely sealed wall all the way to the top where the actual pump works are. Sort of like dunking an upside down glass in a pan of water. The water can run in as long as the air can get out, but not in this case. A simple brake bleeder on the housing would fix all that.

 

The test gauge setup, which could be simplified to just a bleed tube with a valve to control flow, allows the flow to be monitored until all the air is out of the pump. It is the only way to know for sure. The complete setup like mine only costs about the same as a fuel pressure tester.

[Aztec62]

The only way I was able to get fluid to run into the pump was to hold the pump with the motor down at about 45* and rotated so the inlet nipple was pointed upwards slightly. That did reward me with a steady stream of bubbles out of the pump and into my fluid container. It took several minutes for the stream to stop and I then turned the assembly so the pump was straight down for 30seconds or so and returned to the 45* position with the nipple upwards. A few more bubbles appeared and that was about it. The amount of total fluid into the pump was 20ml. The accumulator does not need to be installed while doing this pump gyration as no fluid will run out of any port as it doesn't get by the non-return valve. I then tried the empty pump housing with the motor and screen removed facing straight up and the total fluid volume that filled that space was 25ml.

 

This is how I got my pump starting to build pressure, too.

Pump/ Motor assembly removed from the car.

Connected 12V DC and fluid from a makeshift reservoir (unfortunately no filter) and,

holding the assembly in my hand, tilting it in all kind of directions until fluid started to appear at the outlets.

(@ 2seater: why fluid would not go past the check valve? It have to!)

Then I quickly installed the pump back into the car and the Teves unit worked.

Only make certain fluid is coming from a filtered source.

 

Henning

[2seater]

I am probably repeating steps you have already tried. I wouldn't have thought the pump would get too contaminated internally as there is a pretty fine screen inside the pump housing to protect it.

[2seater]

I'm sure this is old news to some, especially Henning, but I wanted to post a low res. photo of the pump chamber. The open end of the chamber is oriented pretty close to as installed. The fluid entry hole is near the top, about 12:30-1:00 o'clock. I was incorrect about the plate that covers the pump itself. It is staked in place but the opening is more keyhole shaped so there is a tiny amount of space around the drive disc in the center as well as the inlet opening at 7:00 O'clock. There is a filter screen assembly with a plastic frame (removed for clarity) that fits around the circumference of the chamber to strain the fluid before it can get to the pump.

 

Brake fluid seems to have a pretty good surface tension so bubbles like to stick in place and don't want to change size, so it would seem mild agitation does assist in flooding the chamber. Once filled, it should retain the fluid as long as the inlet is plugged. 

 

 

[Aztec62]

2seater,

I did not think about the filter mesh inside the pump. So my theory why my pump failed (running it without a filter in the reservoir) is pretty much busted. So why did it fail?

 

Inside one of the pumps I have opened, I found a little plastic tube wich formed a ring around the pump motor shaft.

It was not connected to anything, just lying there inside the ring filter mesh. Unfortunately, I do not have a photo.

Have you ever seen something like this?

 

Henning

[2seater]

I have not seen any loose parts inside the housing and pretty sure it shouldn't be there. The only think I could speculate it would be is the seal for the end of the motor shaft. The motor shaft is about .315" and the outer diameter of the seal is .630". Hard to see inside the seal but the open side faces out from the motor with what appears to be tiny garter spring around the inner part against the shaft.

 

If the seal came apart I would think it should have stayed on the shaft unless it came apart in pieces which could be drawn into the pump itself? That would likely not be a good thing as there is nothing between the motor and the pump to protect it.

[Aztec62]

2seater,

it is not a seal. I will make a photo next weekend.

 

Henning

[2seater]

Very interesting. I was sure you would recognize a seal but it was the only thing I could think of ? Something from the pump itself?? I would love to see a photo.

[Aztec62]

On 8/29/2017 at 3:22 PM, 2seater said:

Very interesting. I was sure you would recognize a seal but it was the only thing I could think of ? Something from the pump itself?? I would love to see a photo.

 

Well, here are the photos:

 

 

 

[Aztec62]

Today I took an angle grinde and cut the pump body in two.

Here are the photos:

 

 

[Aztec62]