MCI 102C stock webasto info

[buswarrior]

A friend has a 4 stroke C3 with the fans across the back. The D3 and DL3 is likely the same...

Does anyone have a plumbing schematic?
Where do the Webasto lines run, and is there any flow control?

The Webasto in my friend's unit needs to be bypassed due to leaking bits, the coach has to go home for parts and repair.

The commonly available 96/102ABC manual doesn't appear to cover any of the Webasto stuff.

Difficult to coach over the phone without knowing the plumbing and control logic...

Who has a better manual?

Happy coaching!
Buswarrior

[Paso One]

Her is some pictures of whats in a 1996 D3  (burner removed)

[buswarrior]

My concern is advising a bypass strategy or plug it strategy, without knowing the patterns of flow.

Overheating the engine is a potential, if an uninformed choice is made.

What is the flow, from where to where, and is there any valve/control involved?

What would the result be to just put the pipes together, or plug them both?

Happy coaching!
Buswarrior

[Jim Blackwood]

On my DL3 there is a valve on each leg of the run to the heater cores. So on the curb side you can close off the manual valve. On the driver's side close to the webasto is a solenoid type control valve but it only isolates the lines and cores. So plugging the line from the engine to the circulation pump would be the way to go I think.

Jim

[buswarrior]

Jim, is the Webasto plumbed in line to the coach HVAC system?

Or, if there's a control valve, does it go from the hot side, back to the cold side/return to the engine directly?

I am doing this all on the phone with someone who doesn't know...

Happy coaching!
Buswarrior

[Jim Blackwood]

I'll go in a few minutes and look.

Jim

[Paso One]

It appears to me that the engine produces the heat or the Webasto produces the heat, the water is in constant circulation ( on this C10 Cat engine ) as both shut off valves are "after" the heat producers.
Here is more clearer pictures of the Y's .

[Jim Blackwood]

OK I made a drawing but it probably wouldn't photograph well so I'll try to explain it.

First. the heater loop has a manual valve on each leg so it can be shut off entirely.
Then the big solenoid valve short circuits the lines leading to the heater loop.
The engine and webasto are in series, so with the webasto fired up and the solenoid valve open the path of least resistance is through the engine. Assuming the manual valves are also open.
If the solenoid valve is closed. the engine, the webasto, and the heater loop are all in series.

Now I have to make assumptions about flow direction. If the webasto circulation pump is on the cold side for better pump life then flow is through the engine block, out a big casting on the side, through the webasto, through the heater loop (or through the solenoid valve) and back to the water pump housing.

To completely eliminate this system due to leaks both lines to the engine should be detached and plugged. Do not tie them together as this would short circuit the radiator. The two manual valves could be closed to avoid draining the heater loop. The solenoid valve should have little or no effect.

To use the webasto for coach heat only, the simplest solution would be to put a 4 way valve in the lines to the engine to the effect that the engine is removed from the circuit and those two ports blocked with the other two ports connected, but it might not be very easy to find that specific configuration, especially in a solenoid valve and even more in a surplus item.

Jim

[Paso One]

The parts manual shows 4 different illustrations covering the 4 engine options. My pictures are for Cat engine

[buswarrior]

So, in paso's figure, there's a lot of "supply" lines... where is the flow to and from?

Which component, if it fails, would make a feedback loop and overheat the engine?

If that "bypass" valve stays open, where does the flow go?

The coach in question has a cummins.

Thanks, we're getting there...

Happy coaching!
Buswarrior

[Paso One]

Sorry there is only 3 options Cat, Cummins, Detroit.
On this Cat engine I would say there is no way to stop constant flow when engine is running.  Following  the normal assumption that the suction side of the water pump is pulling the flow. Even if one valve was closed it would just go thru the
" y" and continue to flow thru engine and radiators.  I think MCI would not allow an idiot to close a valve and  reduce flow to engine. Also unless  someone added extra valves it's not possible unless thermo was stuck closed. The webasto pump free flows according to service manual

[buswarrior]

Where does the hot output from the webasto go? Labelled as "heater supply" on the figure?

The two "supply" and "return" towards the right side, beyond the two isolation valves are to the coach HVAC?

The webasto gets it's input of coolant from the hot side of the engine, or from the cold side of the HVAC return, via that bypass valve?

Besides the current issues, we all need to know how it works, if we are going to be modifying...

Happy coaching!
Buswarrrior

[Paso One]

Actually the way I see this set up the water is coming from the water supply line on the most left hand side of above picture. It then goes thru the webasto  circulation pump on left side hand side of picture illustrated as a square( cold side ). Then water gets heated and leaves the right hand side of picture.( auxiliary heater) It then goes to the top isolation valve if valve is closed it goes thru the bypass valve and into the  y  just past the lower isolation valve marked on right as return line. The only confusing  part of the diagram is the  word and arrow pointing to the location of the supply its not the actual direction of flow. ( if top isolation valve is open it sends it to front heater)  as you stated, then the return water flow becomes really clear. If the webasto is the only thing working it would get cold water from engine  ( left side  ) and send hot thru the bypass  Y to heat engine.

[Jim Blackwood]

The diagram is accurate for the series 60. the "heater supply" comes from a large casting on the side of the block which also feeds the transmission oil cooler. (This would be the highest pressure in the system, directly connected to the engine pump outlet)

The "return" goes to the water pump housing on the engine. (The line that looks like there's a cap on the end of it. There isn't) The solenoid valve bypasses the heater loop.

The heater loop would be the two lines going forward.

Disregarding the two manual shutoff valves, there are three possible conditions and two possible states, meaning six operational possibilities:
1) Engine on, Webasto on solenoid valve open
2) E O, W O, SX (off)
3) EO, WX, SO
4) EO, WX, SX
5) EX, WO, SO
6) EX, WO, SX
And of course everything off.

To properly do the job all possibilities must be considered and coolant flow analyzed.

It does appear to me that a certain quantity of engine coolant will bypass the radiator in condition 3. Perhaps the lines are sized to take that into account.

Jim

[buswarrior]

Not shown, is the heat control valve for the HVAC, this regularly interupts the water flow through the heater core.

This "bypass valve" that allows coolant to shortcut back to the cold side causes me concern. How does it work, and what is its failure mode? That's an overheated engine looking for a place to happen?

So, if we just plug the ends of the webasto pipes, there's no feed to the HVAC?

Happy coaching!
Buswarrior