PT40 Hydraulic Radiator Fan / Transmission Cooling (Formerly Temps)

[Leroy A. Eckert]

--- In WanderlodgeForum@yahoogroups.com, "Glenn Allen"
wrote:

Glenn: Call me at 850-830-9163. It might be easier to tell you where
to look while next to the bus. I only live about 35 miles away and
would run down on Saturday and maybe we can figure it out. A high idle
could possibly drive up the tranny temp while stationary. The
Alarmstat control unit should be on the left rear of the engine close
to the water pump and the water temp sender. Two wires and looks like
a bulb about 2" in diameter screwed into the water jacket
Leroy Eckert
1990 WB-40 Royale
Dahlonega, GA
Smoke N Mirrors
>
> Pete...Thanks
>
> Leroy,
>
> Your post seems to describe what I observe. I don't know if I have
> an electric or air/electric valve for the override switch. Where is
> this valve located? I would assume I would see an external air line
> going to the valve if it is air/electric and only wires if it is
> electric only.
>
> My fan is operating at idle and picks up a significant speed at
> increased engine RPM. There is a difinite difference in Fan Speed
> between engine idle and 1200 RPM. If I flip the Fan Override switch
> at engine idle, I do not get any change that I notice. I'm trying
> to determine if the FAN is stuck in High or if the FAN is not
> switching to High. While I was previously thinking it was always in
> high, you indicate that there should be elevated RPM even at idle.
> I'm not sure the idle fan speed I have is "elevated" or not. Maybe
> if I locate the valve, then I can switch it with external power to
> determine the condition. I will investigate this avenue to
> determine my state.
>
> All of this became my focus when I recently noticed my transmission
> temp increasing while stopped at a red light. While under way it
> runs 170-180. Engine water temps are fine at all times. I have
> recently changed the internal and external trans filters and fluid.
> Everything looked fine.
>
> If I place the transmission in neutral while stopped (after I notice
> the increase in temp) the temperature will begin decreasing again.
>
> The increase will go over 210 just sitting at idle in gear while
> stopped.
>
> Possible problems:
> 1) The radiator is not cooling properly. I do not think this is the
> problem since the engine temps are OK. However, I am going to clean
> the radiator to be sure it is getting maximum heat transfer.
>
> 2) The transmission heat exchanger is fouled. I'm not sure how to
> test this without draining the radiator coolant and transmission
> fluid. I'll check this out after other possiblities to avoid
> changing fluids again.
>
> 3) The radiator fan is not changing speeds as commanded. Should
> this kick into high sitting at at light while stopped? I'm still
> not sure if I'm stuck in high or low. But I do know that it is not
> changing. I will see if I have a diagram of the fan electrical
> circuit but I don't recall having one. Does anyone have a fan
> override electrical diagram applicable to a 1986 PT40?
>
> 4) Idle Speed is too high. My tach is not functional. This is
> another one of the items on my list. Does anyone know where the
> tach sending unit is located on the 6V92? I'm hoping it is the
> sending unit that needs repaired / replaced and not the Tach since
> the matching Tachs are not available anymore. I will try using an
> external RPM sensor to determine the idle speed until the tach is
> repaired.
>
> 5) Internal problem with transmission....Let's hope its not. My
> local Allison dealer looked at the pan/fluid and said the residue
> looked normal (light amount of fine powder as opposed to metal
> pieces). They suggest that after I have eliminated the cooling
> system as the problem, they can instrument the transmission to
> evaluate it as a possible source of the problem.
>
> Am I missing anything?
>
> Thanks for all the comments / suggestions.
>
> Glenn
> 1986 PT-40
> Marietta, GA
>
>
>
> Re: [WanderlodgeForum] Re: Temps
>
>
> This is related to a 1990 WB-40.
>
> If your coach has an electric fan override yours should be similar
> but not necessarily identical. I have read that certain early models
> operate the fan with an air valve as opposed to electric.
>
> The small radiator that sits on the bottom of the main radiator is a
> Hayden and cools the power steering and hydraulic fan oil. There are
> three filters in the oil reservoir and one Parker canister in line
> filter on the roadside.
>
> If you follow the water hoses they should go to heat exchangers for
> the tranny and engine oil possibly from a manifold on the road side.
> Radiator water cools the engine and tranny oil.
>
> Fan operation if yours is Alarmstat electric control.
> The fan operates in idle(approx. 300-500rpm)except as follows:
> Alarmstat turns on the fan to high mode at 195 degrees and cycles it
> to low mode at about 188 degrees. You should be able to see this
> happen on the water temp gauge while driving. If the temp is not
> reduced to 188 degrees the fan remains in high mode until temps
> reach the lower value of the Alarmstat. The Alarmstat is located at
> or near the water pump in the water jacket. It is a bulb looking
> instrument with two wires. This unit is designed to default to fan
> high mode in the event of failure. Your fan operating in high mode
> at all times could be due to a failed Alarmstat(likely) or the
> Alarmstat has been removed by a PO. or a problem with a a/c/fan relay
> (unlikely) While stationary at idle have someone operate the fan
> override and/or chassis a/c and see if the fan speed changes. There
> is a very noticeable difference.
>
> With the chassis a/c or fan override on the fan runs in high mode
> until either or both are switched off. Switching either one on takes
> the Alarmstat out of the system and runs the fan on high.
>
> My understanding is that engine idle speed provides more than
> adequate fluid volume to operate the fan on full high mode.
>
> My fan enable relay is in the lower load center on an ignition
> circuit.
>
> You need to find someone with 1986 prints for your records. I bet
> someone out there has a set. I have a fan circuit diagram for my
> coach if you want a copy. It may not be identical to your coach.
>
> Leroy Eckert
> 1990 WB-40 Royale
> Dahlonega, GA
> Smoke N Mirrors
>