Jacobs exhaust brake question?

[B.G. Smith]

Just returned from 2,000 mile round trip. Exhaust brake worked great as usual, did notice it coming on when starting truck after rest stop and everything still pretty warm. Was wondering at what temp it comes on to warm up engine after stop and what sensor does it react to? bg

 

[jhenderson]

Mine used to com on at restart when warm, but shut off almost immediately. There's no sensor connected directly to the Jake, it's all controlled through the ECM. If your idle is a little high it might mimic decel and cause the brake to engage. Sorry I'm not more help.

 

[RustyJC]

Deleted - my comment was related to a 2nd gen truck.

Rusty

 

[B.G. Smith]

Rusty, I think mine work the same, the switch was on. jhenderson, when truck is cold and I put it on high idle with exhaust brake on the brake goes off after it gets up to some temperature, less than 190 deg. I just thought it was strange that it was coming on when the truck was still worm, don't know what temperature was but the gauge was about half way up to normal. bg

 

[Ozymandias]

The temperature to switch OFF the brake is fairly high, close to operating temperatur.
Maybe 85°C or something in this range.

I use that feature a lot in winter time and so I know from distant of the truck is ready to go on a cold morning.

 

[ScottLewis]

If I recall, the warmup feature functions at temps below 180*

 

[jhenderson]

Mine was the same. I made the error of assuming warm meant full operating temp.

 

[AH64ID]

As Dan mentioned the ECM uses 180° for the warmup feature. It doesn't take much to get the block to cool down below 180° even on a warm day.

I have seen it take as low as 178° to kick on but it rarely holds until even 181°.

I wouldn't advise using it too much as a warm up aid instead of driving. The exhaust brake can push additional soot into the oil on a cold motor and cold idling is a no-no.

 

[DDozier]

I have 04 an the exhaust brake quit working I have replace the vacuum pump the relay the dump valve an switch I have put the vacuum line directly to the exhaust valve an it activates with pump I test the vacuum pump I have put a vacuum gauge on it it runs at idle 60 an checked the fuse it's good I even replaced hoping it was bad any help would be appreciated thanks DDozier