6B Coolant Plumbing and Flow Questions

[Kevin Cummings]

Hello, I am in the planning stage of installing new SMX Coolant Temperature Alarms on my 370B twins (CPL2208).

I have read thru all of Tony’s tips and also my O&M manual, but need a few clarifications as I plumb in my new hi-temp coolant switches. My Port side is no problem – My Stbd side with existing hot water heater plumbing is a bit more challenging. I read thru the excellent Redundant Alarms article.

My questions relate to the various coolant hoses in the system and trying to understand the coolant flows to determine placement how much coolant to remove before installing new plumbing and hi-temp coolant switches.

Q1). The two vent hoses from the coolant expansion tank:

– One vent hose goes to the area near the temperature sender: Is this hose to allow air/coolant to flow from the block to the expansion tank? Is the flow direction from block to tank?

– Second vent hose goes from expansion tank to the adapter on top of the manifold. Same question – does this hose allow air/coolant flow from block to expansion tank?  Is the flow direction to the tank?

Q2).  What is the purpose of the 1″ hose from the head – located just in front of the heat-exchanger to the coolant pump inlet? Is this the coolant bypass path that it used when the engine is cold and the thermostat is closed (and bypass port open)?  I could not tell from the pictures and  Cummins documentation if the coolant bypass uses an internal path or this is the purpose of the hose.

Q3). What is the purpose of the 3/4″ hose from the expansion tank to the coolant pump inlet? Is this flow constant when engine is hot? This is the hose I use to drain the entire system with a drill pump, but unsure of it’s normal use in the system.

Thank you in advance for clarifying the coolant plumbing flow/hoses, beyond what I can find in the documentation.

Kevin

 

 

Topic

[Tony Athens]

Yes,  the BYPASS  you are searching for is controlled internally thru  the thermostat housing & thermostat design on all B engines. This design came out it in the late 70’s and very early 80’s when the “B” series engine came off the drawing board and was put into production as an industrial engine and has really not changed since.

Must be pushing 10++ millions engine later?

1 user thanked author for this post.

Kevin Cummings

[Kevin Cummings]

Thanks Tony, I’m probably overthinking this setup and your answers make sense to me. I guess I thought that the main coolant return path was via the heat exchanger (when hot?) One followup question – The coolant bypass path – is it via the 1″ hose or some magic internal path. I’m at the end of a long maintenance path over the winter, will send you some pics when done!

 

Update – I just signed up/in for QSOL and can now see the service manual – According to this pic, it appears that the bypass path is an internal passage to the water pump.

Thanks for your help!

Kevin

[Tony Athens]

Simple answers

 

Vent hoses bleed air and coolant to eliminate “air locks” in th closed cooling system . They by-pass the heat X  

 

1″ hose –main return for the entire system to the inlet on the coolant pump ( same as the bottom hose on a car “radiator”

 

3/4″ hose–Make-up hose for vent lines and for filling the system

 

 

[Author]

Replies