Overheating Westerbeke 4-107

[stwagstaff]

The saga continues...

After successfully replacing the oil cooler on my Westerbeke 4-107, I changed out all the fluids. New oil filter, new 15w-40 diesel-rated oil, new antifreeze. Engine starts right up. Took her out for a test drive. Outside the harbor, I opened her up. About a mile out, temperature had pegged to the top of the guage -- 220+.

Killed the motor, dropped anchor, and took apart the raw water pump, even though I was getting a steady stream+spurt out of the exhaust . Impeller looked fine, but I replaced it anyway. Added some coolant to the resevoir. That took long enough for the engine to cool, so I started up -- water flow still looked good -- and I and I limped back in at barely over idle, still close to red-lining on the temperature, between 210-220.

So far, I've taken out the heat exchanger. Zinc was totally rotten away, and there were chips rattling around inside, but the cooler looks otherwise OK. I've flushed a substantial pile of zinc crumbs out and plan to ream it out with a rod later today, to make sure all the tubes are clear. There's a solid flow through the unit if I run water into one side -- it comes through and out the other no problem in both the fresh and saltwater circuits.

I know the gummed up exchanger could bee the main source of the problem -- but what else do I need to do or check? Is it possible there is air trapped that I need to bleed -- maybe in the hot water tank circuit? Also, i'd like to replace the thermostat for good measure, but the Westerbeke manual (Service Bulletin 107) specifies that the Thermostat needs to have a " bypass hole sufficient to allow adequate water flow through the exhaust manifold...", and cautions to use only the original Westerbeke part. The original part is unavailable, of course. Has anyone replaced theirs that can recommend a good unit to use? The one I can find that's supposed to match is a Sierra 23-3653. Does this need modification?

[RayNWanda]

 Give us some history- did the overheat start when you replaced the oil cooler? Which heat exchanger do you have- is it mounted crossways on the back of the engine? Have you done any cooling system replumbing other than changing the oil cooler? There should be a seawater strainer mounted next to the vee drive- check the basket in it. Do you have a Velvet Drive or Paragon?

[SailingSeaDragon]

Stwagstaff,

I have had problems with the W40 overheating in Sea Dragon since the day we brought her home if I ran the engine over 2,300 RPM's for any length of time (30-40 minutes)... I replaced the thermostat, heat exchanger, and "fretted" with this and that for years without success... Last winter I re-plumbed the hot water heater per Westerbeke service bulletin #95 (see below) --- Problem solved. This summer the temp set nicely at 190ish even on the hottest day running at 2,600 RPM's for an extended period...

http://www.sailingseadragon.com/Manuals/DomesticHotWaterHeaterSBulletin7July1980.pdf

I made my H-connection from parts I ordered from McMaster-Carr for less than $20 using standard iron pipe fittings... Logic in using standard "black iron" fittings was 1. I wanted to make sure it helped before shelling out big $$$'s for bronze; 2. It is part of a fresh water (less corrosive) system and should last several seasons without a problem.

I plan to document the process now that the season is over and I had no problems with over heating.

Hope this helps.

Garner

[ishmael]

Agree with Garner.  I had the same issue until I re-plumbed the hot water heater circuit. 

Ron

[stwagstaff]

Wow Garner,
Another great tip about the hot water heater. Thank you. I'm going to go over the system and see how it conforms to the service bulletin.

I took the fresh water heat exchanger off, rinsed out the rotten zinc crumbs, scraped out the heat exchanger tubes and ran water through the whole system to make sure it was running smoothly. It was. I replaced the zinc.  Then I added 50/50 antifreeze/water to the reservoir, making sure all the air was able to bubble out of the system and that the reserve tank was mostly full before I closed it up...and...success! Temp now runs steady at 180-ish, by the gauge, even when I revved her up in the slip for an hour (in gear) and then went for an hour-long cruise in the Bay. I suspect both the gummed up heat exchanger, and the possibility that I hadn't completely filled the  coolant system, as the combined culprits.

Somebody did some interesting plumbing on the fresh water/water heater circuit  on this boat. The coolant reservoir is mounted just under the starboard hatch, directly above the water heater tank, and well above the rest of the engine -- it's the highest point in the whole system. I'm not sure if this is normal - the boat mechanic I had come look at my ruptured oil cooler was surprised to see it. Clearly,  I have to add coolant from this point, or the system doesn't fill completely.

Sean

[Randy]

that's the standard location for the coolant resevoir.

[SVJourney]

That's where our coolant tank is mounted as well.  Nice to be able to check and see the coolant levels. 
(Now if I can just get the oil dipstick to be that easy!)