Coolant leaking from circulating pump

richard5933 · January 27, 2018, 11:38:44 AM

Regardless of how it came to be, the circulating pump is leaking now. I need to either change the seal or the entire pump. I'm guessing that there has been at least a minimal leak at the pump for a short time due to the corrosion on the end of the motor casing.

Anyone ever rebuilt one of these pumps? How about replacing one?

Aside from getting the parts, I'm puzzled how I'm supposed to reach the darned thing. It's one other side of the bay from the access hatch, and even being as small as I am it will be nearly impossible to reach in far enough to use two hands to work on it. Love to hear if someone else did this, and if so was there any access from the bottom by removing the a/c condenser fan.

dtcerrato · January 27, 2018, 11:56:21 AM

You may want or need to create your own access (cut an opening) to get to that rascal...

Templar52 · January 27, 2018, 12:23:41 PM

Luvrbus,
The cooling capacity for 4106 bus is 24 gallons including the heating system,according to the manual. Should be the same for a period Buffalo.

luvrbus · January 27, 2018, 12:46:27 PM

I just did a anti freeze changed on a 4905 and it was 5 ft longer 21 gals with the front heater since the coach heat was removed did one on 4106 without the factory coach heat it only held 18 gals so I don't know what up on the GMs

richard5933 · January 27, 2018, 03:46:28 PM

Here's a couple of pictures of the problems.

Apparently the water modulating valve has been leaking in the past, but it was dry when I tested it this week. I'll have to check again next time I can get it up on the highway for a while.

The circulation pump looks like it has been leaking longer than just a few days. Don't think this leak happened from running it for a few minutes low on coolant the other day. I wouldn't be surprised if this has been leaking for a few years.

The system's total capacity is 92 quarts (23 gallons) per the manual.

I was able to get in the bay through the access hatch, which is about 16" x 16". At least I got my head, shoulders and arms through. What makes it really tough is that the area in front of the access hatch only has about 12" clear before the basement a/c unit. I had to have someone standing by to help get me out. Once inside the bay, I was worried about touching the back of the condenser coil and damaging the fins.

Not sure if I'll be able to do any repairs through the hatch though. Looks like it would be easier to get in from underneath by removing the condenser fan assembly. My goal today was just to verify that if absolutely necessary, I could get my hands on the pump.

I had thought about cutting another way in, but there really isn't one. On the other side of the bulkhead where the pump is mounted is the fuel tank. Across the bulkhead towards the passenger side is the heater core and ventilation unit.

Next step will be to have a chit chat with Luke and see what options exist. That will determine what comes next. As always I welcome any suggestions.

eagle19952 · January 27, 2018, 06:37:03 PM

Those look more like oxidation and electrolysis to me.
Leaks are wet.

richard5933 · January 27, 2018, 07:41:38 PM

Quote from: eagle19952 on January 27, 2018, 06:37:03 PM
Those look more like oxidation and electrolysis to me.
Leaks are wet.

You might be correct about the water modulating valve.

The pump was definitely dripping coolant when I ran it yesterday.

richard5933 · January 28, 2018, 12:11:09 PM

I just was out at the bus and topped off the coolant. Needed another gallon to bring things to the bottom of the filler neck in the surge tank. That makes 8 gallons total, or about 1/3 of the total capacity of the system.

This last fill came after running it for about 45 minutes yesterday to bring the temp to 180 degrees to open the thermostat. I still don't see a drop of coolant anywhere in the engine bay or around the radiator. Not a bit of moisture that I can see around the defroster or the heater core. I checked the oil after full cool down to ambient temp and it is still spot on at the 'full' mark and still looks like just oil (no sign of water or any other contaminant).

This is a lot of coolant to replace. If they didn't fill it properly at the shop could they have missed it by this much? Seems unlikely that the dripping on the circulation booster pump could have caused this much loss on the 40 mile trip home from the shop or the 30 mile drive we took it on the week after. Hasn't moved since then. The OTR heat ran good on warm on both of these trips, so if there was an air pocket it wasn't causing a total airlock to the front of the bus.

The bus is parked on a grade with the nose higher than the tail. If anything that would seem to raise the level at the surge tank, not lower it.

I'm at a loss where the coolant went. Suggestions?

chessie4905 · January 28, 2018, 01:13:53 PM

I don't think they got it full. The switch in the coolant door is there to run the pump to force coolant through heating system to purge trapped air. I don't think coolant can get past pump if it is not on, to purge air in system. That's why the pump switch has to be held in the on position for this purge. Once done, pump runs as needed with normal operation. If you decide to pull pump, after removing clamps, slit the hose lengthwise with a sharp utility knife. Much easier to remove than doing a lot of prying with a screwdriver.

richard5933 · January 28, 2018, 01:32:38 PM

Quote from: chessie4905 on January 28, 2018, 01:13:53 PM
... If you decide to pull pump, after removing clamps, slit the hose lengthwise with a sharp utility knife. Much easier to remove than doing a lot of prying with a screwdriver.

I wish it were as simple as slitting the hose to remove this thing. Take a look at the photo I posted below and you'll see that this is a flange-mounted pump. The flanges mount directly to matching flanges on the ends of the copper piping. I'm anticipating that this is going to be a royal bugger to get out of there. Hopefully the bolts turn and the gaskets let loose. Otherwise I'm on to plan B.

Of course, I'll have to find out what parts are available first...

Templar52 · January 28, 2018, 02:13:26 PM

I have some duos on stock but they are all 12 volts . Is your bus is 24 volts ?

richard5933 · January 28, 2018, 02:23:31 PM

Yup - 24v

chessie4905 · January 28, 2018, 02:32:54 PM

I was talking about the hose connection only. I realize there are also bolts to remove.

richard5933 · January 28, 2018, 03:36:44 PM

Quote from: chessie4905 on January 28, 2018, 02:32:54 PM
I was talking about the hose connection only. I realize there are also bolts to remove.

Maybe I'm confused here. It looks to me like the only thing that connects this pump to the coolant lines are the two flanges. Did I miss something in there?
All I saw in there are two copper lines covered in soft rubber insulation that connect to the pump at the flanges, and the two wires going to the motor.

Our 4106 had rubber hoses, but the one on this 4108 seems to be connected more directly.

I'm not doing well this weekend being patient waiting to talk to Luke - kind of stressed over whether there are parts available. I don't know why this is bothering me so much since I imagine there is a work-around if the pump is not on the shelf. If I know something is repairable I can deal with it, even if it's a big job. It's the not knowing that gets me every time.

From the looks of the manual, the 4108 and the 4905 share the same circulating pump setup.

chessie4905 · January 28, 2018, 04:53:42 PM

Probably same as all 4905s. Shouldn't be a problem getting kit or replacement unit.