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jimbo2013 · 08-08-2014, 06:54 PM

I had a feeling the exhaust butterfly was not closing.

Going down a 8% grade a few weeks ago it wouldn't stay under 45 without a lot a service brakes.

So I tried a few things

I ran next to a barrier wall to listen for the noise, nothing.

it downshifts the tranny for sure

Someone said to put it in the gear that it goes to on normal jake engagement, then hit the brake to see if it slows or makes the exhaust noise....nothing.

How can I really diagnose this.

halfwright · 08-08-2014, 07:17 PM

If you have a butterfly in your exhaust, it is not a jake brake. It is an exhaust brake. And, it is really simple. If it doesn't slow you down, it is not working.

jimbo2013 · 08-08-2014, 07:20 PM

ok how can it be traced out and fixed, I assume there's a solenoid that closes it or something that activates it

Skip426 · 08-08-2014, 07:30 PM

There are multiple controls on the exhaust brake. If the shift pad , indicates 2 with the switch on , then the system is seeing the switch and no throttle applied : if it sees any input from the TPS, it over rides the brake.
There will be a relay and an air solenoid, and an air line to the application air cylinder to be checked out.
Many times the air line is at fault , burnt through , by exhaust heat.
You need to look at the exhaust below the turbo for the air cylinder and trace back the hose to locate the solenoid.
Here's a picture of the exhaust brake , off the engine. Air cylinder is the aluminum tube on top of picture.

halfwright · 08-08-2014, 07:31 PM

Look at the exhuast pipe right behind the turbo. There should be a solenoid and an activation arm mounted on the pipe. Try the arm by hand to see if it is frozen. If not, jumper to the solenoid to see if it activates. That will isolate the problem to the switch or wiring from the switch. Check the fuse. Make sure you have 12 volts to the switch. Then, activate the switch and see if you have 12 volts on the other side off the switch.

jimbo2013 · 08-08-2014, 07:39 PM

ok, thanks, I take look see now I have a starting point

Skip426 · 08-08-2014, 07:43 PM

Quote:

Originally Posted by jimbo2013

ok, thanks, I take look see now I have a starting point

For info on the electrical side , relays etc. Going to need a wiring diagram from your chassis manufacturer.

jimbo2013 · 08-08-2014, 07:49 PM

Quote:

Originally Posted by Skip426

: if it sees any input from the TPS, it over rides the brake.
.

Sorry, what TPS?

It sees the switch that works I see it and it downshifts

Skip426 · 08-08-2014, 08:02 PM

Sorry , TPS =Throttle Positioning Sensor. under the pedal if your coach is anything like mine.

Peralko · 08-08-2014, 08:56 PM

It sounds like you have an exhaust brake. An exhaust brake needs regular maintenance such as lubrication. You have gotten some good info on what to check out, but I would encourage regular maintenance.

ardbark · 08-08-2014, 09:37 PM

Quote:

Originally Posted by halfwright

If you have a butterfly in your exhaust, it is not a jake brake. It is an exhaust brake. And, it is really simple. If it doesn't slow you down, it is not working.

Not to put top fine a point on it but his "exhaust" brake is in all likelihood made by Jacobs Inc, hence the nickname "Jake" brake. Jacobs makes both exhaust and engine braking systems.

Regardless, the OP doesn't say what year his coach is but from the avatar it looks to be late 90s. I have a 96 HR and just changed the Jake, I mean exhaust brake out 2 months ago. They are famous for freezing due to poor engineering and a lack of zirks or any other way to actually get lube on the shaft. It is very easy to remove the end of the air cylinder closest to the air line coming in. Pull this side of the air cylinder off and if you can move the butterfly valve the problem is not with the valve body itself.

If you can't easily move the butterfly valve it is froze. In this case you will need to remove the two V-clamps holding the valve in place, along with the air line going to the air cylinder. If it has never been off you will likely destroy the V-clamps, but they're relatively cheap and your going to need a new gasket (inlet side only) regardless.

There have been reports of having some success freeing up the butterfly if it hasn't been froze for too long. I soaked mine in a bath of penetrating fluid for a week then beat the holy whoop out of it to no avail, then hit it with map gas, then beat on it some more. No dice, had to buy a new one to the tune of nearly $1,000 including new gasket and clamps.

On lube, even with the new valve body in hand there was little hope of getting any meaningful amount of lube into the shaft bores where it is needed most. Just a poor design.

Hope this helps.

hes4all · 08-08-2014, 09:39 PM

All of the above are good suggestion. One other thing to look at is if your brake has flappers. Many exhaust brakes will have one or two flappers in it. They let a predetermine amount of exhaust go by.
A friend of mine had a similar issue and found one of the flappers was missing.
He replaced it and welded them up and it works great now.
Now that might not be the "right" then to do?

JFXG · 08-08-2014, 10:41 PM

Quote:

Originally Posted by ardbark

Not to put top fine a point on it but his "exhaust" brake is in all likelihood made by Jacobs Inc, hence the nickname "Jake" brake. Jacobs makes both exhaust and engine braking systems....

Actually, to put an even finer point on it..... the term "Jake Brake" is more than a nickname. It is a registered trade mark of the Jacobs Company, and they apply this trade mark only to their engine compression brake- the traditional so-called jake brake- which they market as the "Jake Brake (tm) brand engine brake". You are correct in that Jacobs also make several vehicle braking systems, among them a line of exhaust brakes which are marketed as the Jacobs Exhaust Brake (tm).

stik · 08-09-2014, 05:15 AM

Quote:

Originally Posted by JFXG

Actually, to put an even finer point on it..... the term "Jake Brake" is more than a nickname. It is a registered trade mark of the Jacobs Company, and they apply this trade mark only to their engine compression brake- the traditional so-called jake brake- which they market as the "Jake Brake (tm) brand engine brake". You are correct in that Jacobs also make several vehicle braking systems, among them a line of exhaust brakes which are marketed as the Jacobs Exhaust Brake (tm).

U DA MAN!!! Thanks