Over the weekend, the engine in Mondial overheated after running it for about an hour and a half. I was seeing very little water flow out of the exhaust pipe. I changed the impeller and even tried drawing cooling water from a bucket. My guess is that the the water orifice into the mixing elbow has plugged. From reviewing the archives, it's apparent that others have had the same problem. How have you gone about fixing it? Can the mixing elbow be roto-rootered out?

I cleaned out my mixing elbow a while ago by placing it in a bucket with a gallon of Marsolve, then using a small 12-V bilge pump in the bucket to circulate the Marsolve through the water injection port. I let the system run overnight and it seemed to do the job. Later several others pointed out to me that I probably could have taken the elbow to radiator repair shop and got them to chemically clean it out for me with less effort.

I had a similar overheating situation a few years ago on my 1983 #385. After much trouble-shooting with no success, Mack Boring suggested replacing the water pump. Although I had already replaced the impeller and cleaned and checked many other parts, in desperation I replaced the pump and the problem was solved. I think it was about $185

$185.00? Lucky you... I replaced mine in St Thomas and it was $300. And it still didn't fix the problem...which in fact was a collapsed hose somewhere back there. The hose looks fine on the outside but was almost completely blocked. Could save you some $$ if you check that first Joe... C

Had the same problem.
Replaced the mixing elbow ,impeller, flushed the motor twice with marsolve ( was another product but can't remember the name) took out the thermostat,cleaned the raw water filter,
etc. no luck, still overheating especially at higher rpm's.
Then a mechanic pointed to a kink in the hose which goes from the mixing elbow to the muffler.
Flipped the hose and the problem was solved.

I did some diagnostics on Friday of last week. At the outlet of the pump, I'm getting a nice high-pressure stream. By the time it gets to the inlet of the mixing elbow, it's still a stream but it's lost quite a bit of pressure. I wasn't able to test the mixing elbow directly and a friend who owns a auto repair shop told me that no one "tanks" radiators anymore, so I'd have hard time finding a place to get it done. My current thought is to hook up a water supply directly to the mixing elbow and see if we get any water flow out of the exhaust pipe. Any danger of the water backing up into the cylinders?

As far as the block and head are concerned, I doubt it would hurt anything to flush the system with a solvent. I've owned Mondial for 14 years and know that it's never been done before. Having never seen Marsolve in a chandlery, I stopped by Fawcett's (aka Tiffany's on the Severn} figuring that if anybody know of it, they would. Lo and behold, they never heard of it...and referred me to an auto parts store. Where do I find Marsolve?

You can try contacting Marsolve at (203)761-8988 or info@marsolve.com

I have also seen recommendations to use a dilute solution of muriatic acid. You can get muriatic acid at masonry suppliers, possibly some larger home supply stores, and possibly pool suppliers. Muriatic is fairly weak acid but I would still be careful of splashes.

marsolve is out of business.

Look for "Rydlyme"

Had the same problem myself a few yrs ago. Tried everything. Found out that the cap on the raw water filter wasn't seating correctly, and was pulling in air since it is on the vacuum side of the water pump. I replaced the original filter and have never had a problem since.

the mixing elbow is clogged. these generally clog up every 5 years or so. it can be resurrected with muriatic acid, or replaced if the build up is unmanagable.