1009 Engine Revving When Breaking

[Christian]

Hey guys. I'm currently experiencing a weird engine rev. When I pull up to a stop sign and come to a stop, about one in ten times, the engine will rev to ~1500-2000 RPM. No matter how long I wait, it will not slow down on its own. The only way to make it stop is to let off the break and let it drive. Generally, after about a hundred yards or so, it will straighten out and go back down to idle, at which time I can drive on without a problem. It doesn't seem to have any correlation about how quickly I stopped, the speed I was going before I stopped, or how hard or soft I press on the break.

Any idea what could cause this? I've been looking for relevant posts all afternoon and haven't found any.

Also, I'm not sure if it's related, but when I start the truck, it surges to 1500-2000 RPM for about a second, then goes down to normal idle. I still have no idea what is causing this. I've checked for air (put a clear hose coming off the IP return; no bubbles) and run copious amounts of injector cleaner, but still no change. The issue with the breaks is new, the surging has happened since I got the truck.

I really don't want to have to resort to putting it in the diesel shop, but that may be what I end up having to do.

Thanks,
Christian

 

[Keith_J]

Sounds like the hydroboost is loading down the power steering pump which is affecting the injection pump's low speed governing system.

 

[Bethelfire]

Could be you cold high idle solenoid......try unplugging it.

 

[Keith_J]

Yes, try the fast cold idle solenoid disconnect. But the link between brake and the problem is in the hydroboost, there is nothing between the solenoid and brake.

You could try removing right side alternator and power steering belt but you should never drive it with these two disconnected.

 

[Christian]

Tomorrow I'll try disconnecting the fast cold idle solenoid. The issue I face when testing this is how intermittent the problem actually is is. I can get all the way to school, work, then back home (about 20 miles) and it won't do it once, then the next day it will do it at every stop sign. I haven't noticed a correlation between frequency and temperature or driving style or anything. Makes me think hydroboost since it is definitely break related. What would cause the hydroboost to "load down" the PS pump?

 

[Keith_J]

In circuit hydraulic systems, there is a high pressure side and a return to tank/pump side. If there is a leak between the two where the fluid is doing no work, the pump still sees the work, only manifestation of work is the fluid temperature on the return is higher. Heat is work is energy. Work is pressure x volume.

A pump moving 1 gallon per minute at 3000 PSI is performing 1.75 Hp of work. IIRC, the pump on CUCVs flows about 5 gallons/minute at 2000 PSI.

 

[Mainsail]

I've been looking for relevant posts all afternoon and haven't found any.

This thread will be difficult to find in the future as well. Seriously hope it isn't taken the wrong way, but they're brakes, not breaks (unless they're broken). The search engine won't work for the next person looking for brake or brakes or braking. No worries, the keywords are in the thread now.