I am having a 740B dumper with parking brake problem. The parking brake hold or slowly disengage when I disengage and try moving it. In order to disengage completely, I have to accelerate the machine at neutral ( no gear selected) before it is released. Then I put it in Drive to move further without any issue. If not it continues to hold why driving. This trick has to be continue anytime I hold the brake in order to Drive freely.
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740B parking brake issue
- Thread starter Atanda
- Start date
Having a little bit of trouble understanding the exact issue, parking brake takes an extended time to release, is that correct? First off, what is serial number of machine. Secondly, do you have access to cat ET so you can read what the parking brake pressure sensor is reading? System should have an accumulator in it and there’s also an orifice fitting on the inlet of the parking brake valve, I have seen those get plugged and cause a slow release or a no release situation. Once you post a serial number I’ll be able to look up accurate information.
We’ll get some pressures to support that theory and post them. Without the serial number I can’t tell you exactly but on the T4R 740B, the parking brake release pressure comes from the brake piston pump and is in excess of 3000 psi and does not come from the pilot pump.
nowing75
Senior Member
I agree with ahart. Have had the problem with the orifice geting pluged a few times. Easy to check
Where do I get the serial number, I can only see product identification number. But I told my technicians to service the pilot pump and it was fine now hoping it will take some time. This seems to be a temporary solution anyway. I should have taking the psi but I don't have access to the pressure gauge atm.
Nige
Senior Member
No. Machine Serial Number is the last 8 characters of the 17-character PIN, in your case B1P04441.
So it appears that this is not a 740B as previously stated, rather a straight 740. Parking brake release system is much the same though you will need a pressure gauge to test. Can you give more details on how servicing the pilot pump was a temporary solution? I can’t quite figure out where we are in the diagnostic process or how you plan to complete it without pressure gauges.
Well, I am a junior Engineer in the company with no enough tools. I requested for them and they don't come. All I have to do is loose the pump and clean everything with diesel. The inside is dirty with sand(mud) . We have to scrap some parts with sandpaper. Sorry I did not take pictures when working on it.
