Viscuous Heater Relay Pull and Opposite Effect

Greaser · **Posted:** Sun Apr 03, 2011 9:44 am

I pulled my Viscuous Heater Relay and checked a tank (mpg's) and it dropped, a lot, few things I noticed, and not that it would suprise anyone, but it took longer for the Jeep to warm up, at least by a couple of miles before it got to operating temp. And I wonder if that is the reason I lost MPG's instead of gain, I can see this helping out someone who has a bad Thermostat, but since mine is brand new, it made it worse. If you want to see how it tracked you can check my Fuelly at the bottom of the page. Oh and I am in South East Wisconsin and temp ranged from 30-50 degrees.

uham · **Joined:** Tue Nov 30, 2010 10:48 am **Posts:** 37

Greaser,
I pulled my Viscuous Heater Relay about two weeks ago and it improved my mileage from 28MPG to 30MPG on the EVIC. I live in South Florida where it's always HOT. Near 80 most of the time. Also, the idle is smoother after start up in the morning. This may be a summertime fix for a lot of CRD's.

METCRD · **Posted:** Sun Apr 03, 2011 7:20 pm

Greaser, I agree with Uham, I think that pulling the VH relay during the colder months will have a negative affect on fuel economy as the jeep will take longer to warm up. I live in NE Ohio and pulled my relay as well about 3 weeks ago. I debated on plugging it back in during these most recent colder temps but decided to see the affects on the economy. Also the bugger was just plain hard to take out with my bare hands and being so close to warmer temps that aided in my decision to leave it out. I will be plugging it back in this fall when the temps get lower.

dgeist · **Posted:** Tue Apr 05, 2011 5:06 pm

Yep, mostly us folks south of the Mason-Dixon line can benefit from it year-round (that's the southern border of Pennsylvania for anyone who's US-history challenged). It's also really nice if you have a t-stat that's already failing....

Dan

bhc04 · **Posted:** Tue Apr 05, 2011 8:05 pm

Just pulled my #36 relay today. Will see if it makes any difference in MPG. Here in Bullhead City, AZ. usually never gets below 40 deg. in winter.

SPN-87 · **Joined:** Tue Mar 09, 2010 3:09 pm **Posts:** 53

Pulled my #36 relay - DTC B10B3 and P1202 appeared.
Any ideas ?

WolverineFW · **Posted:** Tue Apr 26, 2011 8:44 pm

SPN-87 wrote:

Pulled my #36 relay - DTC B10B3 and P1202 appeared.
Any ideas ?

B10B3-VISCOUS/CABIN HEATER RELAY CONTROL OPEN CIRCUIT

P1202 - FUEL SYSTEM OVER-PRESSURE - Stuck Regulator (Diesel)

uham · **Joined:** Tue Nov 30, 2010 10:48 am **Posts:** 37

Looks like most of the relay pulls were on the 2005 CRD. Are the codes only appearing on the 2006? Has anyone pulled the relay on a 2006 and not seen DTC B10B3 or P1202?

bhc04 · **Posted:** Wed Apr 27, 2011 12:10 am

uham wrote:

Looks like most of the relay pulls were on the 2005 CRD. Are the codes only appearing on the 2006? Has anyone pulled the relay on a 2006 and not seen DTC B10B3 or P1202?

I pulled mine on my 06 and haven't seen any codes. A.C. seems to get colder which is nice in AZ.

warp2diesel · **Posted:** Wed Apr 27, 2011 10:11 am

Quick warm ups reduce cylinder wear and ring wear, that is why there is a Viscous Heater.
VW TDIs put Glow Plugs (three on my Wife's) into the heater hose outlet so the defroster works.
But when you live in the South where it is hot a lot, the Viscous Heater is useless to say the least.

One observation I have traveling around the country is that there are people every where who idle their engines for 10 to 20 min to warm up the engine. Since the most ring and cylinder wall wear happens during engine warm up, the quicker you can get the engine up to temp, the better. As long as you wait for the engine oil light to go off and the engine to smooth out enough so it does not stall, that is all you need to do before you start going. Even with a hotel right off the expressway exit ramp, you will drive enough to get the oil up to the cam shafts before you accelerate to merge.
Since all vehicles get ZERO MPG at idle, it makes sense to get going as soon as the engine has oil pressure and smooths out enough to go. At -15F if I can't plug in, it only takes about 20 to 30 seconds with my CRD before I am comfortable in putting it into gear and pulling out onto the street, I don't need to run it for a half hour like some do. :banghead:

I have used this trick for years to save fuel and reduce engine wear, I hope most on this Forum do the same.

dieseldoesit · **Posted:** Wed Apr 27, 2011 10:39 am

warp2diesel wrote:

Quick warm ups reduce cylinder wear and ring wear, that is why there is a Viscous Heater.
VW TDIs put Glow Plugs (three on my Wife's) into the heater hose outlet so the defroster works.
But when you live in the South where it is hot a lot, the Viscous Heater is useless to say the least.

One observation I have traveling around the country is that there are people every where who idle their engines for 10 to 20 min to warm up the engine. Since the most ring and cylinder wall wear happens during engine warm up, the quicker you can get the engine up to temp, the better. As long as you wait for the engine oil light to go off and the engine to smooth out enough so it does not stall, that is all you need to do before you start going. Even with a hotel right off the expressway exit ramp, you will drive enough to get the oil up to the cam shafts before you accelerate to merge.
Since all vehicles get ZERO MPG at idle, it makes sense to get going as soon as the engine has oil pressure and smooths out enough to go. At -15F if I can't plug in, it only takes about 20 to 30 seconds with my CRD before I am comfortable in putting it into gear and pulling out onto the street, I don't need to run it for a half hour like some do. :banghead:

I have used this trick for years to save fuel and reduce engine wear, I hope most on this Forum do the same.

agreed, I start it up and go, unless it is really cold out and the engine is cold as well.

warp2diesel · **Posted:** Wed Apr 27, 2011 11:03 am

dieseldoesit wrote:

warp2diesel wrote:

Quick warm ups reduce cylinder wear and ring wear, that is why there is a Viscous Heater.
VW TDIs put Glow Plugs (three on my Wife's) into the heater hose outlet so the defroster works.
But when you live in the South where it is hot a lot, the Viscous Heater is useless to say the least.

One observation I have traveling around the country is that there are people every where who idle their engines for 10 to 20 min to warm up the engine. Since the most ring and cylinder wall wear happens during engine warm up, the quicker you can get the engine up to temp, the better. As long as you wait for the engine oil light to go off and the engine to smooth out enough so it does not stall, that is all you need to do before you start going. Even with a hotel right off the expressway exit ramp, you will drive enough to get the oil up to the cam shafts before you accelerate to merge.
Since all vehicles get ZERO MPG at idle, it makes sense to get going as soon as the engine has oil pressure and smooths out enough to go. At -15F if I can't plug in, it only takes about 20 to 30 seconds with my CRD before I am comfortable in putting it into gear and pulling out onto the street, I don't need to run it for a half hour like some do. :banghead:

I have used this trick for years to save fuel and reduce engine wear, I hope most on this Forum do the same.

agreed, I start it up and go, unless it is really cold out and the engine is cold as well.

May I add, this practice is responsible resource (your money) and responsible environmental management that does not repress personal freedom.

dieseldoesit · **Posted:** Wed Apr 27, 2011 11:16 am

warp2diesel wrote:

May I add, this practice is responsible resource (your money) and responsible environmental management that does not repress personal freedom.

No.

papaindigo · **Posted:** Wed Apr 27, 2011 11:27 am

I'd be curious what GDE has to say particularly for those of us with a tune as that lowers the viscous heater shut-off threshold which I presume means it turns off at a lower temperature. As I understand it, could be wrong, the main purpose of the viscous heater is to get some cabin heat early in the warm up cycle but how much the viscous heater actually contributes to engine warm up I don't know but GDE might. I do know that if I plug in the OEM engine heater that I get some cabin heat immediately after cranking up so I suspect in that situation the viscous heater runs little if at all. Of course given my location cold is not that big an issue as +20F is considered fridged for here.

I do know based on 2 Dodge D-250 Cummins and 3 CRDs that operating at idle to warm up the engine is a waste of time and fuel as diesel engines simply won't warm up at idle in any reasonable length of time so I agree with warp. Crank it up and idle briefly then drive although I prefer to not jump straight to freeway speed at least not until I see some signs of life from the temp gauge.

So far with the viscous heater relay pulled no codes and it looks like a bump of 1-2 mpg in town from 22ish to 24ish, I wouldn't anticipate any improvement on the highway.

warp2diesel · **Posted:** Wed Apr 27, 2011 1:08 pm

dieseldoesit wrote:

warp2diesel wrote:

May I add, this practice is responsible resource (your money) and responsible environmental management that does not repress personal freedom.

No.

It looks like our Distinguished Acting Professor of Chemistry has his perspective limited to his specific trade judging by his last comment, even though he follows the intelligent practice :banghead:

warp2diesel · **Posted:** Wed Apr 27, 2011 1:14 pm

papaindigo wrote:

I'd be curious what GDE has to say particularly for those of us with a tune as that lowers the viscous heater shut-off threshold which I presume means it turns off at a lower temperature. As I understand it, could be wrong, the main purpose of the viscous heater is to get some cabin heat early in the warm up cycle but how much the viscous heater actually contributes to engine warm up I don't know but GDE might. I do know that if I plug in the OEM engine heater that I get some cabin heat immediately after cranking up so I suspect in that situation the viscous heater runs little if at all. Of course given my location cold is not that big an issue as +20F is considered fridged for here.

I do know based on 2 Dodge D-250 Cummins and 3 CRDs that operating at idle to warm up the engine is a waste of time and fuel as diesel engines simply won't warm up at idle in any reasonable length of time so I agree with warp. Crank it up and idle briefly then drive although I prefer to not jump straight to freeway speed at least not until I see some signs of life from the temp gauge.

So far with the viscous heater relay pulled no codes and it looks like a bump of 1-2 mpg in town from 22ish to 24ish, I wouldn't anticipate any improvement on the highway.

An example of Responsible Environmental Management is shown in papaindigo's post.
Perhaps the ADD Council needs a Public Service Commercial showing a younger guy with a lifted SUV telling an old guy that warming up a modern engine by idling is IRRESPONSIBLE!
Some States like New York have State Laws and other areas have Local Ordinances prohibiting idling when no one is in the vehicle. Police do issue very casshy tickets.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The viscous heater on the KJ is primarily used to build cabin heat quicker. Close to 90% of engine wear occurs during the first 30 seconds of operation. Once the oil pressure is good the wear stops for the most part. We lowered the VH shut off threshold for very cold climates due to constant cycling with the stock tune. This is just one more fuel economy enabler.

The newest diesels in Europe do not have any sort of add-on coolant heater as they are older technology. Most are using PTC heaters placed directly in the vehicles HVAC air ducts to provide instantaneous heat right after the start. A PTC heater is very similar to a hair dryer, just a heater element with air blowing across it. Granted this puts a big load on the alternator, which in turn means more fuel burning and helps to heat up the engine a bit.

I agree that you should just drive normally during the warm-up period to get the engine up to operating temp quicker. Excessive idling can lead to more wear on the cylinders due to wall wetting from unburned fuel. In some cases it can lead to oil dilution if much unburnt fuel gets past the rings. Extended idle time dramatically increases the hydrocarbon emissions (partial combustion). Notice a truck stop were the guys idle for hours at a time, the exhaust will have a whitish-bluish tinge to it...all hydrocarbon.

Our CRDs were made to run hard, babying them only leads to more soot build up and stuff breaking.

dgeist · **Posted:** Thu Apr 28, 2011 3:14 pm

GreenDieselEngineering wrote:

Our CRDs were made to run hard, babying them only leads to more soot build up and stuff breaking.

...except for the torque converter. Be careful with that :wink:

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

Of course...some parts were never meant to stay stock!

Viscuous Heater Relay Pull and Opposite Effect

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