Jake Brake Operation

[dbothwell]

This is the first time I've posted a question on this site (which is my excuse for posting this same question in the "second gen" forum)!



Anyway, I recently had a Jake Brake installed by my local Dodge dealer who told me that I could leave it turned on all the time. It came with an on/off swith mounted on the 6 speed gear shift and after turning it on and off a few times I found it more convenient to just leave it turned on. This way when I let off the go pedal it really slows things down. I've been very impressed with the unit so far (this is my first diesel truck).



I am just curious, however. Is there any downside to leaving the exhaust brake turned on all the time? I haven't seen any so far.

 

[CROW]

dbothwell: Good Question. Got mine installed earlier this month and was wondering the same thing so guys we need help. Info that came with the brake indicated that it would only work when the truck was not being fueled and when the brake is turned on. That sorta indicates the brake will be turned off if you are adding fuel.

Other Questions:

1. Will the brake work when the engine idle automatically ramps up to 1,000 rpm in cold weather. I'd prefer to be able to manually run the idle up to 1,000 or so with the brake on to aid in warm up, but according to the info that came with the brake, it will go off if you add fuel.

2. Will there be a problem with excess heat at idle with the brake on after the engine is at operating temperature.

My truck is a 2003 HO.

 

[JStieger]

other questions

Some other questions -



1)Is the Jake strong enough to lock up the wheels when the road is wet or otherwise slick?

2)Does the Jake engaged sound like the big rigs or is it fairly quiet?

3) Is it possible to do a partial engagement of the Jake as opposed to full on/off to control the degree of braking?



Thanks!

 

[Ladders]

OK, heres MY opinion and ONLY mine...



Leaving it on when shutting down is not too great, it holds the heat in. Turn it off before you get to the parking spot.



In answer to the other ques:



1. YES, I think that MAY have contributed to the roll-over of DRIFTY as I think the brake was on when I started to peddle brake on the black ice.

2. NO, it sounds more like a jet eng (hissing) altho the 03's may sound different.

3. You could try adding a pressure/vacume (depends on which style you have) adjuster and that could do it. EDIT: Was reading the E-brake manual and it says not to operate the vacume pump w/o a load as it will destroy the pump. MAY want to ask Carlton Bale (sp) who posts on here and works for Jacobs.



Now for my ques: I just added the pyro to the brake (dlr let me have the unit to do it before the install) and put it on the ground spot UNDER the elbow (the short bend side) so that the wire comes up by the vacume tip on the E-brake. I hope this clears all other parts after install. Did this after looking at how it was to be installed and this made sense as it could be reached from the fender well. Yes the probe is before the diaphragm and is not in its way. Is this BAD???



Cause if it is, OOOPPPPS..... gonna have2buy another one which is not gud... .



HEHEHEHE. . hope to get it by the weekend but doubt it. Probably wont b at the dlrs till Friday and with all the other dlr adds could be Tue/Wed next week



Anyhows;

soons 2b "SOTS" agn

\\BF//

 

[Dean Upson]

I always left the Jacob's Brake on my 98. 5 in dry weather. I never had any problems with overheating. The brake won't lock up the wheels but it sure would put you in harms way on slippery pavement. Use of the ebrake sure saves the service brakes. It makes sense to shut the brake off to cool down the motor while idling. Wouldn't the truck be shut down when adding fuel?



Dean

 

[dbothwell]

Thanks for the input so far. In response to a couple of questions above,



1. I've left mine activated on wet roads and have not had any problem with the rear wheels losing traction. Ice would surely be another story.



2. From the cab of my 03 it kinda sounds like a "big rig" when I'm decellerating (but quieter - at least to my ear). However, when idling it definately makes a hissing noise when activated.



3. The gear shift mounted switch that comes with the unit is strictly on / off. You can't vary the amount of breaking force applied.

 

[dbothwell]

Thanks for the input so far. In response to a couple of questions above,



1. I've left mine activated on wet roads and have not had any problem with the rear wheels losing traction. Ice would surely be another story.



2. From the cab of my 03 it kinda sounds like a "big rig" when I'm decellerating (but quieter - at least to my ear). However, when idling it definately makes a hissing noise when activated.



3. The gear shift mounted switch that comes with the unit is strictly on / off. You can't vary the amount of breaking force applied.

 

[Dean Upson]

Braking force is determined by rpm. The lower the gear you are in (higher rpm), the greater the effectiveness of the exhaust brake. I would add wet leaves to the list of slippery surfaces (especially when there is frost).



Dean

 

[Ladders]

In addition to my earlier post, finished reading the instructions and it says to leave it off on wet/slippery roads BUT, yes it does help on wet roads. I would make sure that you test it and if unloaded YOU MAY (key word MAY) have some rear wheel lock-up.

Agn, this is probably a "legal" issue with its usage, if you "crash" they wont be responsible (nor I). As with anything - proceed with caution and realize each situation is different.

Of course, when I gets mine, will test all aspects of it. and the truck



soons 2b "SOTSU" agn

\\BF//

 

[Fireman]

That is alot of questions

I don't see any harm in leaving the brake on all of the time. I talked to a Pac Brake dealer once who said that he has no switch, therefore the brake is always on. I am sure that it "could" cause a loss of traction on wet roads, but I have never had a problem. I've been driving Fire Trucks with Jacobs engine brakes for 15-20 yrs. , the only time we turn them off is on the rare occasions that we have ice or snow. If your engine gets to hot the exhaust brake will shut off at idle. I don't remember the temp, but it's somewhere over 200F. Mine has never gotten hot enough to shut off. I've never had either type of Jake Brake lock up the rear wheels. The exhaust brake is very quiet and doesn't make the brat-t-t-t-t-t sound that the engine brakes do. Only the engine brakes ( they actually hold the exhaust valves) are adjustable.

 

[jmbrowning]

Re: That is alot of questions

Originally posted by Fireman

I don't see any harm in leaving the brake on all of the time... ... If your engine gets to hot the exhaust brake will shut off at idle... .

I don't believe that the brake would make the engine too hot in normal operation, however if the brake is operating at idle the EGT will never go under 300* (most likely way over 300) and therefore the turbo will be too hot for shutdown.

 

[Fireman]

Good point, I am still waiting on my pyrometer so i have no idea what the EGT is when idleing



Fireman

 

[ImagesThatSing]

How hot is too hot to shut down?

""don't believe that the brake would make the engine too hot in normal operation, however if the brake is operating at idle the EGT will never go under 300* (most likely way over 300) and therefore the turbo will be too hot for shutdown""



How hot is too hot for shutdown? 300* didn't seem to hot to me so guess I should know what is the threshold.

 

[JStieger]

Lots of good info off this site - all my questions and then some answered!



Can an engine brake as opposed to an exhaust brake be installed on these 5. 9? Or is it just cost prohibitive / over-kill for what we use them for? As part of a work project a year ago I did some ride-alongs with some trucks hauling our mine ore (129,000 lbs gross) to another mine. They had these 3-stage brakes that had some serious retarding power. These trucks had some some big Cummins or 525 Cat engines and 18 speeds could climb those interstate and steep highway hills at a pretty good clip too... but I digress...

 

[Dean Upson]

My guess is the engine brake would be cost prohibitive and not needed in a pickup truck. My own experience with the Jacobs exhaust brake has been pretty positive.



Dean

 

[David Oxland]

I can confirm that mine retarded enough to come down to idle speed on ice even with a 1000 # of tongue weight over the back axle. Got to be on your toes if you're going to play this game

David

 

[jcarew]

pac brake safety

I recently had a pac-brake installed on my 002 6spd and while playing with it to get the hang of how it effects the feel of the truck. I began to wonder what the effect would be to a car following to close talking on the phone or eating drinking etc. the stopping power is like a good shot of service brakes except the stop-lights do not work with it. am I missing something in my installation, or is it let the follower beware. Mine really hauls down if you flip it on an then go from 6th to 5th. just a thought .

 

[Ladders]

More info gotten

An e-brake in most areas is NOT considered an ENGine brake and therefore usable where the Eng brake is not.



Also, after driving mine (about 130 miles on it now) with the e-brake on, found out it shuts off it the eng temp is up and you are stopped for a period of time (traffic lites, stop signs, idleing @ your favorite spot, etc. So this answers the ques about leaving it on all the time. Just have to wait a little longer b4 shutting down the Mighty CUMMINs! So, when I get my probes hooked up, will find out how much this affects the shutdown time if left on. It may take a while b4 they are fully operational but the probe is in on the brake elbow, just gots to rewire things, add things, drill the b4 probe and wire it all up. Probably another week or so (depends when we make trips that we NEED 2 take (Alaska, AZ, east coast, etc) and how much time I have).



SOTSU!

\\BF//

 

[SteveH]

I live in a pretty cold climate and have tried to "warm up" the engine like some have mentioned with the Jake Brake. There is no difference in warming up before or after the Jake Brake installation. Since there is no "thermosiphoning" of the air through the turbo/engine/exhause while the engine is shut down; there can be no "holding of the heat in the engine. " The Jake Brake does exactly what it was designed for, slowing down the rig without depending completely on the pull vehicle's brakes.

Just my 2 cents worth.

Steve H.

 

[Robin]

There is some confusion about Jake brakes and exhaust brakes. Over the years it has become common usage to call the Jacobs Engine Brake a Jake brake, even though Jacobs makes both the engine brake (Jake brake) and an exhaust brake. So it is incorrect to call an exhaust brake a Jake brake even though it might be made by Jacobs



A Cummins "B" series engine such as in Dodges or the "C" series used in motor homes cannot have a Jake brake installed because the fuel is injected by an injection pump. This applied to any Diesel engine with an injection pump as opposed to cam operated injectors.



On a Diesel engine with cam operated injectors a true Jake brake works like this. During normal operation while pulling: In each cylinder the cycle is in five steps like a gasoline engine' 1. a downward intake stroke where a cam opens the intake valve drawing in air but with with no fuel; 2. the upward compression stroke where the air taken in is compressed and reaches a high temperature; 3. At or near the top of the compression stroke, a cam punches the injector which squirts in fuel; The fuel burns because of the high temperature, oxygen rich compressed air; 4; The downward power stoke where the burning fuel forces the piston down; 5. The upward exhaust stroke where a cam opens the exhaust valves for the whole upward stroke.



When the Jake engine brake is turned on, there is a linkage that is shifted which causes the injector cam to no longer operate the injector, rather it operates the exhaust valve.



The Jake brake cycles are like this: During the downward intake stroke the intake valve is open same as normal operation and air is drawn in. 2. The upward compression stroke compresses the air same as normal operation; 3. Here's where the difference is, instead of the injector cam punching the injector, it punches the exhaust valve, opening it briefly. The compressed air is discharged explosively. There is no power stroke because the compressed air had been released and the cam does not inject any fuel. So the piston goes on the the next intake stroke.



This explosive discharge of air is what caused the braaaap sound.



A Diesel engine is notoriously poor as a retarding device as opposed to a gasoline engine. When no fuel is being fed by the injectors, the energy used to highly compress the air is nearly all returned by this compressed air pushing back down on the piston during the no-fuel power stroke. When the throttle is shut off on a gasoline engine, there is a retarding force commonly called compression braking. It is more accurately called vacuum braking because each piston is struggling to pull air in through the closed throttle plate during the intake stroke. This is the where the retarding force comes from, not compression. This is why a lot of blue smoke comes from a worn gasoline engine when descending a grade with the throttle closed. The vacuum pulls in oil past worn valve seals and worn piston rings.



Hope this clears up nomenclature and why a "B" engine cannot have a Jake brake. Sorry for getting long winded.



Bob