New user here!

I have a 98.5 cummins 24V.

The brake seem rock hard. I can stop but have to apply a lot more pressure than my 1500 gasser.
I know these run off the PS pump. Any easy way to quick test booster?
Also what kind of PS fluid should I use in it?

Thanks!

 

Check the owners manual and the p/s dipstick for oil type. Check the color of the fluid and condition, does it smell bad, brown, or burnt? You could try flushing the p/s system fluid as well. Check for oil leaks around the booster at the firewall and look inside under the dash where the push rod comes through. See if there is any oil there or running down the firewall. After that there isn't much you can do on your own. Hope this helps.

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Just thought of something else. If there is a rubber pressure hose between the pump and the booster then you could try to disconnect it and check the flow to the booster. Old hoses can deteriorate and act like a one way valve but I would do that last.