Coolant leaking from circulating pump

richard5933 · January 26, 2018, 02:19:57 PM

We had a somewhat warm day today so I thought I'd run the generator and bus engine to get their fluids moving. First time for the bus engine since parking it about two months ago.

Funny thing happened when trying to start it. Temp was around 45F, so it fired right up. Smoked for a brief minute and smoothed out right away. About 20 seconds later it just cut out. Waited a minute or two, restarted with no problem. This happened a few times till I noticed the low water light was on each time.

I then checked the surge tank and it was low. Added 3-1/2 gallons of coolant mix and she started up again with no problems. Ran the motor on fast idle for about 5 minutes and the buzzer started to indicate low water again. Went out to get more coolant and added another 3-1/2 gallons. Ran it on fast idle until the engine temp hit 180 and the thermostat opened. I search everywhere that I can think of but can find no coolant leaking. The oil level is normal and there is no indication of coolant in the oil.

This coach does NOT have a Webasto or Aqua Hot. Just the OTR heater, which worked just like it should today. No leaks in engine compartment, no leaks around defroster core, no leaks visible around heater core.

Only thing I can think of is that the shop didn't fully fill the coolant when they had it in late fall. The last thing they did was install the block heater. I ran it home from the shop, and then for another very short trip a week or so later. Temps have been cold (very cold) since then.

It's quite a bit of coolant to replace and I am somewhat concerned. You'd think that there would be a puddle under the bus, but since we're parked over fine gravel I'd never see it if it was a slow leak. I'll keep my eyes on the lookout but so far I see nothing dripping since shutting down an hour ago.

Any thoughts where to look for the missing coolant?

Oonrahnjay · January 26, 2018, 03:00:50 PM

Look for yogurt on the dipstick???

richard5933 · January 26, 2018, 03:29:44 PM

Oil looks just fine.

I think I found the leak. The a/c condenser is located in the first bay driver's side. There is an access hatch on the rear side of the a/c bay in the bulkhead that can be accessed from the next bay to the rear.

I opened the access hatch, and all the way on on the front of the bay is the heater circulating pump. It's bolted to the copper coolant lines and had a electric motor. Sure enough, there is a slow drip coming from the circulating pump.

Assuming that I can get a replacement pump, I'll need to practice my contortionist moves to get to the darn thing. Pulling the condenser would allow access, but that would require evacuating (and later refilling) the refrigerant. This coach is still running the original refrigerant, so I don't want to touch this.

If I had a way to get under the bus I'm sure that there is access through the bottom of the bay, since the condenser fan vents down and has a removable screen over it. This might be a job for the shop - not sure yet. Sure wish this was as easy to get to on the 4108 as it is on the 4106 - that one was right out in the open.

Funny thing is reading through the service manual bit about all this. They make it sound like you can just reach in there and pull the pump with no problem. Apparently at one time it was possible to get a rebuild kit for the pump and motor. Not sure what's available now, and won't know till Monday when I can talk to Luke.

Anyone have experience with this? Anyone know if the pumps or parts are still available? Since the whole purpose of this pump is just to move coolant around, I'm assuming that if the OEM pump is not repairable or replaceable it will be possible to retrofit something else to do the job. What fun.
Trying not to stress out over this...

bobofthenorth · January 26, 2018, 04:53:28 PM

Years ago I added a magnetic drive pump to circulate the coolant through the house radiators on our bus. If you end up replacing the pump take a look at the mag drive pumps because they get completely away from seals which means your leak can't happen.

chessie4905 · January 26, 2018, 05:34:01 PM

I would call Luke. If it is still available, either pump or kit, he can most likely get it or has it.

richard5933 · January 26, 2018, 05:58:54 PM

On my list for Monday morning to call Luke. I was hoping someone else has done this and could let me know how it went.

Templar52 · January 26, 2018, 06:04:11 PM

Sir,it may be just the gaskets between the pump and the modulating valve. I remember a few years ago,we installed some special gaskets over there. Thoses gaskets were ticker and stronger than the originals one.
If ever the motor is defect,everyting is rebuild able...

richard5933 · January 26, 2018, 06:33:53 PM

Seems to be dripping directly from the pump, just below the place where the shaft/seals are. Gaskets look like they've seeped in the past, but they are dry now.

The service manual has instructions for rebuilding the pump and motor, but doing that will depend solely on the parts available.

buswarrior · January 27, 2018, 07:46:52 AM

The important lesson for busnuts in this?

Check fluids before start, ESPECIALLY after a period of storage.

Check EVERYTHING after the shop has had it. Hired help doesn't give 2 hoots about your stuff.

Good fortune this time!

Your protection from the bus demons is now expired...!

happy coaching!
buswarrior

Templar52 · January 27, 2018, 08:05:36 AM

Whent the shop refill your engine after the installation of your block heater,they probabely did not start the circulating pump to fill the heater and defroster water circuit. They should have closed the two valves to isolate the bus heating system before draining your engine .They probabely forget to do So.
You say that you put 7 gallons of antifreeze back in the surge tank.....certainly not a dripping circulating pump.

luvrbus · January 27, 2018, 08:09:20 AM

If you have silicone hoses (the blue one) they leak during cold weather I tighten mine all the time when the weather gets cooler

richard5933 · January 27, 2018, 09:24:03 AM

Quote from: Templar52 on January 27, 2018, 08:05:36 AM
Whent the shop refill your engine after the installation of your block heater,they probabely did not start the circulating pump to fill the heater and defroster water circuit. They should have closed the two valves to isolate the bus heating system before draining your engine .They probabely forget to do So.
You say that you put 7 gallons of antifreeze back in the surge tank.....certainly not a dripping circulating pump.

There are anywhere from 75,000 to 90,000 drops of water per gallon, depending on who you ask.

The pump drips about once every 5 seconds when running the pump with the engine at fast idle. That's about 720 drops an hour. Even if the number of drops/gallon for coolant is only 50,000 it would take about 70 hours to drip through one gallon. I've driven the bus about 20 hours total, at most. That would bring me to less than half a gallon lost through dripping. Even if I double the rate of dripping for operation on the highway, it still only accounts for one gallon of coolant loss.

I still want to get it fixed, as I have no idea when it will fail further and empty out the entire cooling system.

That of course brings me to the problem of where all the rest of the coolant went. I opened the access hatch to the heater core and to the defroster core. Both are dry and show no signs of having anything more than some condensation over the years. No dried puddles of coolant, no stains, no corrosion. Even the a/c bay with the dripping pump doesn't really show signs that it's been dripping for that long. All the basement bays are dry. There is no sign of even a drip in the engine bay. Engine oil is fine and at the proper level. No smoke or haze in the exhaust. Can't figure out where the coolant went.

Only thing I can figure at this point is the shop didn't properly fill the thing up when I had them install the block heater. The low-water sensor didn't trigger at the time - maybe the warmer weather at the time kept it from reading low? Maybe there was a large air pocket that finally made it's way to the surge tank? Don't really know.

Anyone have suggestions on where else to look for possible leaks?

Templar52 · January 27, 2018, 09:38:15 AM

I think Richard that there is no leak at all.
The shop did not full the system. They probabely stay with some gallons of antifreeze that was impossible to them to put back in the tank. They do not taught were the rest of the coolant was for. Whent you start your bus last time you brobabely switch on the heater and the circulating pump take some water from the engine to send it to the defroster or heating radiator who were empty at the time. 7 gallons is approximately what the heating system use.
So don't worry...be happy that this problem appear on your driveway and not on the freeway.

dtcerrato · January 27, 2018, 10:33:18 AM

I agree wit Templar52
That may be the very reason why your coolant circulating pump is leaking now - for it may have ran "dry" for a spell and coprimised the seal...

luvrbus · January 27, 2018, 11:34:51 AM

His bus should take 19 gals for the entire system ? how much coolant will the heater and lines take to fill,the engine alone holds 8 gals,then radiators on buses take the same amount or more that only leaves 3 gals if my math is correct 7 gals of coolant is a lot that is over a 1/3 of the total capacity of the system,he has a leak some where