Community Forums

SteveR161 · 05-23-2011, 09:11 PM

We experienced a coolant leak today on a trip from Cottonwood Az to Cortez Co. the coolant was leaking above the rear differential on the driver's side frame rail. I suspected a heater hose as the feed and return lines pass through this area. It is a cluster of electical wires, air lines, etc in this area. We have a 2002 MADP 3954 with a cummins ISL 370.
To get me to the campground, I created a bypass with the heater hoses by connecting the inlet to the outlet on the engine block. This got me by but there is still coolant leaking above the rear differential on the driver's side frame rail.
Is there anything in this area that requires engine coolant that I am missing?
Are there more than 2 lines for the cockpit heater system?
All input is greatly appreciated.

Mr_D · 05-23-2011, 09:27 PM

Have you checked you coolant filter? Usually it's further toward the rear but if it's leaking the fluid might be spraying forward and fooling you.

SteveR161 · 05-23-2011, 09:47 PM

The coolant filter seems dry, mine is located right next to the engine oil filter.

Barlow46 · 05-23-2011, 11:53 PM

Do you have a coolant hose near there that runs up to the turbo area?

GaryKD · 05-24-2011, 08:12 AM

Hi SteveR161,
There is a lot of coolant in in the line no longer being used. It may take a while to drain out.

dons2346 · 05-24-2011, 09:24 AM

Do you have a water heater that uses engine coolant to heat water while on the road? Could be a line for that.

SteveR161 · 05-24-2011, 09:46 AM

As for the extra coolant in the long lines to the cockpit area, I thought of that, but the coolant level kept dropping. I had the low coolant light come on twice in 40 miles. I stoppped and refilled once and arrived at the CG with the low coolant light on and buzzing.

I think the turbo is oil lubed only.

I have the hydro hot system and thought that this system was self contained. I've looked this system over as well as done some repairs to this system and don't recall seeing any engine coolant line feeding the hydro hot.
Am I wrong?

I will crawl under the coach today and try to unscramble the wiring mess to locate the leaking line.

deandec · 05-24-2011, 10:29 AM

We have two school bus water pumps installed by the manufacturer that are prone to leaking and failure.

One is near the rear differential, the other is behind the front "bumper". They serve to move hot coolant to the dash heater and then on to the water heater while enroute. They are always electrified whether needed or not.

I have removed the pump in the rear because it left me stranded one time on the freeway in Eastern Montana by dumping my coolant.

The intent was to repair or replace the pump, but the bypass does not seem to affect either my domestic water heating or the cab heat generated, so it remains bypassed and removed.

Maybe you have a similar setup?

SteveR161 · 05-24-2011, 05:10 PM

Well it was a coolant line that feeds the Hydro Hot system. The line splits over the rear differential along the drivers side frame rail. Not sure how it circulates with only one feed and then a split. It was a bugger to change but all is well now,
About $75 in parts and coolant and a few hours labor.
Thanks for all the suggestions.
With every issue that arises, I learn something new about the coach systems.