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SW-48 Hydraulic pressure relief

8

88jeepyj

New member
Hi i'm new here!

I'm partially restoring a mid 80's Bombardier SW-48 that i picked up for short money. It has a 6 cyl. Ford and 3 speed auto transmission.

My question is:

How does the hydraulic system relieve pressure on these machines? The pump spins freely by hand, but when the engine is started, the pump will not spin with the engine as it is kicking back against the belt and slipping it.

I'm curious as to where the stuck check-valve may be. In the pump or valvebody? Any help would be appreciated. Thanks!
 
where the stuck check-valve may be. In the pump or valvebody? Quote...



If it is on the valve body, it would be fairly easy to determine as it would look like a large cap with a hex at it's base on the side or possibly the end of the valve body. What type of pump do these have? If it is gear type, the relief is likely inthe valve body.

Hope this might help,

Kirk
 
300 H and H said:
where the stuck check-valve may be. In the pump or valvebody? Quote...



If it is on the valve body, it would be fairly easy to determine as it would look like a large cap with a hex at it's base on the side or possibly the end of the valve body. What type of pump do these have? If it is gear type, the relief is likely inthe valve body.

Hope this might help,

Kirk
Click to expand...

If it is the standard pump it is a vane pump, which is why you can turn it by hand it will not pump till the vanes are spun out. (starts with no load that way)
And if it is standard plumbing the pump has a internal relief with a small hose back to take and the valve has one also under the acorn hex cap. Make sure your suction side is not plugged also.
 
sounds like these have a vickers vtm pump a word to the wise if your relief valve is stuck or has some debries in it you can split the housing also look at the return hose off the relief port if it is kinked it can cause the same problem don't try to shim the relief spring or modify the valve it will not control the pressure right and split the housing its a bout 27 bucks for a valve and spring cheap compaired to the 300 bucks for the housing. i learned this lesson through the school of hard knocks.
 
dds said:
sounds like these have a vickers vtm pump a word to the wise if your relief valve is stuck or has some debries in it you can split the housing also look at the return hose off the relief port if it is kinked it can cause the same problem don't try to shim the relief spring or modify the valve it will not control the pressure right and split the housing its a bout 27 bucks for a valve and spring cheap compaired to the 300 bucks for the housing. i learned this lesson through the school of hard knocks.
Click to expand...

Thanks for you advice, i imagine its just stuck or clogged. I had a feeling that the pump had one as well as the valvebody. I'll let you guys know how i fixed it.
 
88jeepyj said:
Thanks for you advice, i imagine its just stuck or clogged. I had a feeling that the pump had one as well as the valvebody. I'll let you guys know how i fixed it.
Click to expand...

If it has the standard pump looking down from the top you will see a Roll pin
Below it is the pump relief.
 
I walked over and looked at it, i see the hole with a roll pin. I'm going to see what i can do later this afternoon.
 
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