[char1355]

There is another way to gain another port on that back cylinder. Engines where the port in the head was being used had a plate on the back of the block for the air compressor outlet. You remove the rear freeze plug and mount the plate there. I may have one of those laying around somewhere. The main part is Cummins 3925226, the 1/2" pipe plug in the back is 3008468, the 2 bolts are 3910495 which are M12x1.75x30 flange head (2 req), and the sealing O ring is 3910530. The issue with that part could be it won't clear certain engine adapter plates. The ones found on the industrial engine that had this part were SAE3. The Ford or GM plates may have a hump sticking up that would block using that part. I never test fitted it on one so don't know. Also, if engine to firewall clearance is tight that may not work either. Part is about 1.5" thick or a tad more.

 

[Blaster]

There is another way to gain another port on that back cylinder. Engines where the port in the head was being used had a plate on the back of the block for the air compressor outlet. You remove the rear freeze plug and mount the plate there. I may have one of those laying around somewhere. The main part is Cummins 3925226, the 1/2" pipe plug in the back is 3008468, the 2 bolts are 3910495 which are M12x1.75x30 flange head (2 req), and the sealing O ring is 3910530. The issue with that part could be it won't clear certain engine adapter plates. The ones found on the industrial engine that had this part were SAE3. The Ford or GM plates may have a hump sticking up that would block using that part. I never test fitted it on one so don't know. Also, if engine to firewall clearance is tight that may not work either. Part is about 1.5" thick or a tad more.

On the very back of the block? Looks handy but if it’s where I’m thinking that’s not an option. But I did find a solution I feel good about. So it turns out 14mm is not much bigger than 1/4 NPT. The old threads were still visible after I drilled out the hole.

 

[char1355]

May have some idea for your switch location. The original location for the wax motor type KSB switch is not at the back end. There is another port in the center of the head just below the intake plenum. That is where the KSB switch goes. Unless you have a late model replacement head there should be a 1/2" pipe plug there. Here's a photo of a original 4bt showing that location. That switch turns on when the coolant reaches around 160 deg F. The rear port was used for coolant return on engines with air compressors or a secondary temp sensor or switch. Some applications had a warning light or buzzer in case the driver wasn't paying attention to the gauge or the gauge sensor had gone bad. If you head has both plugs then you could put the fan sensor in that rear plug. All this doesn't matter because I looked back at your photos and you do not have the wax motor KSB. Yours is the solenoid type. The sensor for that one mounts in the intake manifold plate. It is an air sensor set at around 90 deg F, not a water type. Also, it is normally on unit until the preset temp is reached where the wax type is normally off until the temp is reached. Below is the Cummins diagram for your type. Be sure you have the right sensor or the KSB may be working in reverse.

 

[Blaster]

May have some idea for your switch location. The original location for the wax motor type KSB switch is not at the back end. There is another port in the center of the head just below the intake plenum. That is where the KSB switch goes. Unless you have a late model replacement head there should be a 1/2" pipe plug there. Here's a photo of a original 4bt showing that location. That switch turns on when the coolant reaches around 160 deg F. The rear port was used for coolant return on engines with air compressors or a secondary temp sensor or switch. Some applications had a warning light or buzzer in case the driver wasn't paying attention to the gauge or the gauge sensor had gone bad. If you head has both plugs then you could put the fan sensor in that rear plug. All this doesn't matter because I looked back at your photos and you do not have the wax motor KSB. Yours is the solenoid type. The sensor for that one mounts in the intake manifold plate. It is an air sensor set at around 90 deg F, not a water type. Also, it is normally on unit until the preset temp is reached where the wax type is normally off until the temp is reached. Below is the Cummins diagram for your type. Be sure you have the right sensor or the KSB may be working in reverse.

I’ll have to look around for a switch. But just doing a google search for 4bt ksb thermal switch is no good. Unless I have the name wrong all that shows up is thermostats, fuel solenoids and ksb wiring.

 

[char1355]

The manifold switch for the solenoid type KSB is Cummins part 3921642. There may be other numbers that have replace that. Saw one on ebay for $28.50. it's the same one used on the Dodge 5.9 up thru 1993. Be glad you don't have the wax motor type as that switch is near $200. Haven't found a part number for the wiring harness for that one on a 4bt. It may be 3923303 but that is not certain. Pretty certain that's the one used on the 6bt Dodge and the 4bt may use the same one. Again, that one is not horribly expensive. Saw one on ebay for around $40. The one for the wax motor type is near $200. They just didn't make as many of the wax type and they've been discontinued for a long time.

 

[Blaster]

The manifold switch for the solenoid type KSB is Cummins part 3921642. There may be other numbers that have replace that. Saw one on ebay for $28.50. it's the same one used on the Dodge 5.9 up thru 1993. Be glad you don't have the wax motor type as that switch is near $200. Haven't found a part number for the wiring harness for that one on a 4bt. It may be 3923303 but that is not certain. Pretty certain that's the one used on the 6bt Dodge and the 4bt may use the same one. Again, that one is not horribly expensive. Saw one on ebay for around $40. The one for the wax motor type is near $200. They just didn't make as many of the wax type and they've been discontinued for a long time.

So the one I have is a 2 blade style and it has numbers on just about every side of the hex. 803/1/19 120°, 95°C plus or -3°C, 103, 6-24v 3w, VDO made in Germany. Using a voltmeter I’m not getting a continuity test. Could this be a fan switch?

 

[char1355]

The part 3921642 has been replaced by part 4327029. See photo below. That VDO 803/1/19 is a water temp sender for a gauge, not a switch, and works only with a VDO gauge. The KSB air sensor is set for 90 deg F and installs in the intake manifold plate like the 3921500 shown below. The sensor is located in the port closest to the intake opening.

 

[Blaster]

The part 3921642 has been replaced by part 4327029. See photo below. That VDO 803/1/19 is a water temp sender for a gauge, not a switch, and works only with a VDO gauge. The KSB air sensor is set for 90 deg F and installs in the intake manifold plate like the 3921500 shown below. The sensor is located in the port closest to the intake opening.

So is there a switch for the coolant? I don’t have a intake manifold with a port.

 

[char1355]

There is a coolant switch but it is made for the wax motor type KSB but won't work with the solenoid type. It's also super expensive. The wax motor switch is normally open and doesn't turn on until coolant temp reaches 160 deg F. It's of the same order as a cooling fan switch. The solenoid type you have has a switch which is normally closed and turns off when air temp reaches 90 deg F. Did a little looking and found normally closed switches in ratings of 150 and 165 deg. either of those should be OK. They install with 1/2" NPT which fits the port on the head for a water switch. No idea as to price but don't expect them to be real cheap. May be the reason Cummins went with the air type. I did notice that many of their switches are Horton brand which trigger the cooling fans found on big trucks. Here's a link to that site. https://www.indexsensors.com/pdfs/hd_temp_sw_cp.pdf Did a little more looking and found a listing for the switch 8037107 which is the 165 deg for $78.97 at a site fanclutch.com. They also have the 8037121 which is the 150 deg but it is 3/8" NPT and would require and adapter to fit 1/2". It's the same price. Here's a link to that site. Index Sensors & Controls Control/Sensor/Switch 8037107 | FanClutch.com | 800-525-0164

 

[Blaster]

There is a coolant switch but it is made for the wax motor type KSB but won't work with the solenoid type. It's also super expensive. The wax motor switch is normally open and doesn't turn on until coolant temp reaches 160 deg F. It's of the same order as a cooling fan switch. The solenoid type you have has a switch which is normally closed and turns off when air temp reaches 90 deg F. Did a little looking and found normally closed switches in ratings of 150 and 165 deg. either of those should be OK. They install with 1/2" NPT which fits the port on the head for a water switch. No idea as to price but don't expect them to be real cheap. May be the reason Cummins went with the air type. I did notice that many of their switches are Horton brand which trigger the cooling fans found on big trucks. Here's a link to that site. https://www.indexsensors.com/pdfs/hd_temp_sw_cp.pdf Did a little more looking and found a listing for the switch 8037107 which is the 165 deg for $78.97 at a site fanclutch.com. They also have the 8037121 which is the 150 deg but it is 3/8" NPT and would require and adapter to fit 1/2". It's the same price. Here's a link to that site. Index Sensors & Controls Control/Sensor/Switch 8037107 | FanClutch.com | 800-525-0164

So my intake manifold has no port for a ksb. But what about this plug on the side of the head. Could that be used for the Switch? One thing im confused about for the Thermo switch is it seems to be a 3 prong connector. So you get power to it and then from there down to the solenoid. What's the 3rd wire for? The pigtail is 3823255.

 

[char1355]

Your intake plate must be one of the aftermaket units. If that port on the head goes into the intake chamber you could use it but it may be of little use if you use the intake heater. The heat from that unit would raise the air temp around that sensor to 90 deg F before it could ever turn on. Here shows the location of the sensor on a 6bt and the 4bt would have been similar. It's well away from the intake heater.

 

[Blaster]

So I came across this one for ksb wiring. I was concerned that the ksb switch has 3 wires. But according to this manual the center prong/wire are unused.

 

[char1355]

Yes, that is correct. Although the plug has provision for 3 wires only 2 are used. Just 12V in and 12V out.

 

[Blaster]

Well a little progress is progress and that’s what counts right. I got the belt tensioner bracket made and another alternator bracket. I need to pick up a shorter serpentine belt 54 inches is what I would like. And I’ll have to change it all up again in the future when I finally get air-conditioning. I’m waiting for a new lower radiator inlet to come in so I can change the direction of that. Of the lower radiator hoses. The Thermal switch for the KSB finally arrived. Also waiting on shock hoops. I sprayed some lizard skin thermal and sound control on part of the firewall so I can get my foot peeled and stuff mounted up and out of the way so I can dress up the engine bay a bit more.

 

[Blaster]

So I took the old bracket and welded on an extension. Drilled and filed out a couple square holes for the throttle and eventually cruise control.

 

[Blaster]

Just dressing up wires and a few other things.

 

[edpruss]

There is no law that says engine must be in the center, I see you have already built engine mounts, but if you moved it slightly to the starboard side, it would help your diff. clearance.

Ed in CO.

 

[Blaster]

There is no law that says engine must be in the center, I see you have already built engine mounts, but if you moved it slightly to the starboard side, it would help your diff. clearance.

Ed in CO.

I actually did move it over as far as the motor mount bushing would let me. But I would like just a little more. Here is a little of a before and after. I welded an extension on the left side"Drivers side". and pushed the bushing all the way over as much as it could.

Before

After

Driver side further from the frame

Passenger side as close as the rubber would allow.