Universal Diesel M18 overheating and coolant escaping from bleeder problems

[mforum]

I found a few drops of coolant periodically below the engine and suspected an old hose with leak from the freshwater pump to the heat exchanger. I drained the coolant from the manifold and block with a little more than 2 quarts.

M18 manual says the coolant capacity is 3 quarts. I changed the hose. I added about 1.5 quarts which filled to about 1 inch below manifold cap as shown in picture 1.

I ran the engine at idle waiting for temperature to rise but the temperature gauge was sticky and jumped from < 120 F to > 280 F. I immediately shut down the engine, waited for it to cool down and checked the manifold which looked empty. See picture 2. I added more coolant back up to 1 inch below manifold cap and idled the motor again.

At low idle and low temp no coolant would escape from what I think is the coolant bleeder. I’ve run the engine at idle for several minutes while warm but not hot with coolant bleeder open and closed. As soon as I increase above idle or temperature starts to rise, coolant will start to leak from the coolant bleeder valve. I’ve tried running the engine to 2800 to 3000 rpm for a few seconds to try to remove air as described in the manual but coolant continues to leak from the bleeder despite trying this several times.

My questions are:
Is coolant still escaping from the bleeder because there is still air in the coolant system lines which is expanding and increasing pressure in the system when heated forcing coolant through the bleeder?
Is this a thermostat problem?
Is this a heat exchanger problem?
Is this a hose or line blockage problem?

I welcome any thoughts and suggestions about what I should try next to solve this problem.

 

[jviss]

Maybe you should replace that bleeder valve! They are cheap.

 

[jviss]

I had a Universal M25. I learned that one of the best ways of filling it with coolant was to pump it in from the drain petcock with that thermostat housing bleeder open.

 

[captcoho]

Search past threads, some people added a coolant overflow tank to M18

 

[BarryL]

Hello,

Do you have water heater that uses engine coolant to heat the water? If so then you probably have an air bubble, It can be very difficult to get the air out and the right amount of coolant in. I had a similar problem when my water heater died and I replaced it. It took over 3 go arounds of adding coolant, running the engine, getting overheating, adding coolant, etc. I did a bunch of searches and eventually found a way of getting the air out.

Good luck,
Barry

 

[TimFromLI]

Are you sure the water is circulating? Is there possibly a blockage in the heat exchanger, the fresh water pump is working? try removing the thermostat. That bleeder valve looks to be the highest point in the system, if coolant escapes, there shouldn't be any air. I had an m25 that had one hose higher than the manifold that was difficult to bleed. I had to remove it, pour coolant into it, put my thumb over the end and reattach to get past the air lock.

 

[mforum]

I suspect air in the system more likely than blockage since there has been no over heating in the 3 years I‘ve owned the boat with a new heat exchanger at that time.

At low idle before temperature increases, there is no coolant escaping through the bleeder valve and the engine can run like this for 5-10 minutes with the coolant and engine only getting warm. There was probably a half a quart difference in coolant added from what I drained from the petcock on the starboard side of the engine block.

There is an overflow hose without a tank connected to the manifold cap but it has never leaked any coolant except after I installed the new hose and added new coolant and then only a small amount.

I’m going to try JVISS’s idea of pushing coolant in through the petcock drain in the block which appears to be close to the lowest point in the system, then cycle engine, overheat, add coolant a few times before checking thermostat and then heat exchanger. I’m not sure if I have a hot water heater, what it looks like or where it would be located.

 

[BarryL]

Hey,

To find a water heater you need to trace the coolant lines. From the water pump (not raw water pump but coolant pump) there should be two black hoses. One carries hot water to the water heater and then heat exchanger, the other carries the 'now' cooled water back to the engine block. The correct routing is Engine - Water Heater - Heat Exchanger - back to engine, but some are plumbed to go to the heat exchanger first. Either way, the water heater will have 4 water connections - two COOLANT lines to heat the water, a COLD water inlet and a HOT water output. There is another heat exchanger inside the water heater. The hot engine coolant is used to heat the water inside the water tank.

This is a picture of the M-18 that was in my 1986 Newport 28. The black hoses at the top carry coolant to / from the water heater and heat exchanger. Follow those. If all you find if the heat exchanger then you don't have a water heater.
I bet that if you can 'burp' the engine a few times you will get the air out and that will solve your problem.

This seems to be a common problem

air lock on water heater from engine coolant side

Is there a technique to purge any air pocket from the water heater lines. After replaceing collant hose and water pump, engine overheats within minutes or withen an hour. Steam pressure develops at highest point due to air pocket at water heater and causes engine to over heat. I Removed the...

forums.sailboatowners.com

Hope this helps.

Barry

I’m not sure if I have a hot water heater, what it looks like or where it would be located.

 

[jviss]

If all you find if the heat exchanger then you don't have a water heater.

Also, if you turn on the hot water tap after running the engine for 30 or more minutes and no hot water comes out, then you probably don't have a water heater.

 

[Stu Jackson]

in the 3 years I‘ve owned the boat

I’m not sure if I have a hot water heater, what it looks like or where it would be located.

Excuse my exasperation, but you've owned the boat for 3 years and you don't know if you have a water heater or not? Really?
Do you not have a manual for your boat? Almost every single Catalina boat made has active, helpful owners associations, who usually have their own websites, most of which offer copies or PDFs of the boat's manuals.
A Google search for "+catalina+27" found this in less than a minute:

Catalina 27 Manuals | Catalina 27

A list of engine, owners', and other useful manuals for the Catalina 27 sailboat.

www.catalina27.net

 

[jviss]

I've had my boat for 4 1/2 years now, and I still can't find the macerator.

 

[mforum]

Pushed the coolant with a large syringe through the block coolant drain. Felt resistance, no coolant came out the coolant air bleed, opened the coolant cap and coolant flowed out the top.

Idled motor with engine in forward and slowly warmed up. Air/coolant hissed through coolant air bleed but eventually stopped after about 15 minutes. Engine runs fine now at 160F after warm up. When I increase from idle to about 2100 rpm I find coolant dripping from what I think is the bottom side of the manifold just forward of what appears to be the exhaust flange. Do I have a crack in the manifold? It doesn’t seem like it’s coming from any of the hoses or connects going to the manifold or heat exchanger.

 

[jviss]

Loose manifold, manifold gasket, who knows?