Coolant change M35B

[John Langford]

I went to change my M35B engine coolant for the first time and ran into a snag or two. First, the manual points you to coolant drain plug on the starboard side of the block above the forward engine mount. But when I opened the plug and took off the radiator cap I got no flow whatsoever. I noticed in a later M35B manual from Westerbeke that they show a picture of a different drain plug but I can't locate anything resembling that drawing on the engine.

I then wondered if undoing the petcock on the heat exchanger would drain the block as well as the HX but it didn't want to move with hand pressure and I was reluctant to put a tool to the flimsy handle.

Finally, the manual shows a petcock on the top of the thermostat for bleeding air while refilling. I have no petcock in that location so I was wondering what alternative techniques M35B owners have resorted to...assuming I can get the old coolant out:)

I have searched the archives but found nothing specific on a M35B coolant change. Any advice appreciated.

[Stu Jackson]

John,

Try reply #6 here on Burping your engine, discusses a way to remove coolant without using the engine block petcock. http://c34.org/bbs/index.php/topic,4518.0.html   I've looked at some photos of the M35 that Tony Wright had posted, but didn't see a comparable easy to get to hose from the freshwater circulating pump.  Good luck.

The HX has the engine antifreeze coolant in the tubes, not the shell, so i don't know how you'd do anything with the HX.

Tapping into any of the hoses with the engine coolant in it would do.

[Ron Hill]

John : I believe that the plug that you are looking for to drain the internal coolant (50/50% Prestone/water) is on the port side of your engine just under the alternator.  You might think of getting yourself a petcock so when to remove the plug you can replace it with a petcock rather than the plug (local Kubota dealer).

I believe that the "butterfly valve" on the HX will remove the coolant as removing the Zn will remove coolant raw water.  Let me check. 

[mainesail]

I believe that the "butterfly valve" on the HX will remove the coolant as removing the Zn will remove coolant raw water.  Let me check.  

Ron you are correct, at least on all the Universal/Westerbeke HX's I've worked on.

You can see in this photo that the pet-cock is in the sealed system side of the HX and the zinc is in the raw water side. Perhaps they made them where this was not the case, but I have yet to come across one..

[John Langford]

Thanks guys. That's very helpful. I will look on the port side of the engine but of course that is a lot easier said than done on the C34.

Re the HX petcock valve. Does it drain the block as well? Also, any further advice on handling a petcock valve when turning the handle by hand produces no results? It doesn't look like the kind of thing that wants to be forced. Perhaps I can probably take off one of the coolant hoses at the HX instead.

[Ron Hill]

John : If you turn the petcock "butterfly" valve and nothing comes out here's what I'd do.  Open that valve and take a piece of wire and try to clean out the clog.  If that doesn't work, take a open end wrench and remove the entire valve, drain it and replace it with a new valve assembly (same thing for the muffler drain if you need to use it)

The coolant plug on the port side of the engine block does drain the block.  It's been my experience that you can never get all of the coolant out of the block, hoses and water heater.  Try some pressure in the radiator cap and it will force out a bit more.  No need to worry unless you are adding a new coolant that is NOT compatable with the coolant that you already have in the engine. 

Coolant does not "wear out". The lubricant and rust inhibitor additive qualities do deteriorate with time.   A few thoughts

[John Langford]

Thanks Ron. I read your mind and put a small wrench to the petcock handle earlier today assuming that I could replace the whole assembly if it broke. In fact, it did not and coolant came dribbling out slowly but persistently. I also put a pump on the end of one of the water heater hoses at the coolant pump and got a quart or so out of that system independently. With the amount sucked out of the reservoir added it is beginning to look like a very respectable bucketful of old coolant.

Does anyone bother with a fresh water or chemical flushing on the coolant side before refilling? The drain process is so slow that I am not sure that anything I dislodge with "Super Flush" would actually find its way out of the HX.

[jfssail]

Good point John, when I changed the coolant on my M35A, I first drained the system by disconnecting both hoses at the hot water heater. Used a hose to flush the heater, and flush the engine. Let the system drain and refilled with 2 gallons of distilled water. Drained the distilled water after bringing the engine up to temperature and then draining the distilled water and refilling with 60/40 Prestone.

Jack F Stewart
1993 C36 #1233 "Windancer"
Port Clinton, OH

[Ron Hill]

John : There was a recent post where a C34 owner flushed out his system with fresh water after he used it to help the impeller.
I commented "what a great idea" for a number of reasons.  I wouldn't do it after each use, but it's like fresh water in the head system if you're going to leave the boat set for a week or so to control the smell. 
I'm not too sure if the fresh water will help the impeller - it surely won't hinder, but it will "sure as hell" will help the inside of the HX, the inside of the raw water pump and prolong the Zinc's life. 

I'm going to rig up a "Y" valve and flush out that system with fresh water, just like I spray fresh water on my new anchor chain after it's pulled in!  Why let these items set in salt water when it only takes a minute or so to do a flush?  A thought

[John Langford]

To complete the coolant change saga. I used a small funnel to fill up both water heater lines with coolant and reattached them. I then filled the manifold, opened the HX petcock again briefly to be sure that the HX was filling up and then closed the petcock. I  ran the engine with the radiator cap off and after a short while the level of fluid in the manifold went down but the engine temperature gauge went through the ceiling so I turned the engine off. I noticed that the engine block itself wasn't that hot but the thermostat housing where the sender is located was. So after things cooled down, I pulled one of the water heater hoses off the water pump housing and used the funnel to fill up the pump body with coolant. That did the trick. The airlock disappeared, the engine ran solidly at 160F and the water heater produced the normal "hot" water. I then refilled the reservoir to midpoint and checked the coolant change off my To Do list. I reckon I got out and put in about 5 litres of coolant - close enough for a Canadian to the advertised 6 quarts.

One final point for M35 B owners. The HX petcock drain is a far easier to access than the drain on the port side of the block. It is also lower down than the block drain.

[mainesail]

To complete the coolant change saga. I used a small funnel to fill up both water heater lines with coolant and reattached them. I then filled the manifold, opened the HX petcock again briefly to be sure that the HX was filling up and then closed the petcock. I  ran the engine with the radiator cap off and after a short while the level of fluid in the manifold went down but the engine temperature gauge went through the ceiling so I turned the engine off. I noticed that the engine block itself wasn't that hot but the thermostat housing where the sender is located was. So after things cooled down, I pulled one of the water heater hoses off the water pump housing and used the funnel to fill up the pump body with coolant. That did the trick. The airlock disappeared, the engine ran solidly at 160F and the water heater produced the normal "hot" water. I then refilled the reservoir to midpoint and checked the coolant change off my To Do list. I reckon I got out and put in about 5 litres of coolant - close enough for a Canadian to the advertised 6 quarts.

One final point for M35 B owners. The HX petcock drain is a far easier to access than the drain on the port side of the block. It is also lower down than the block drain.

An easy way to bleed is to replace the side mounted pet cock on the M-35 t-stat housing with a quarter turn ball valve, a plastic elbow and some hose. This hose now becomes your new high point in the system. You can crack the ball valve and not burn your hands and still purge all the air. I have been rigging my boats like this for years. Probably should have got a patent on it, cause it works sooo well....


What it looks like on my Westerbeke. On the M-35 it would just come in from the side.

[Ron Hill]

Main : Great idea !  I believe that most of the M35BC engines have both available side ports from the thermostate filled.  One has a sender to the temp gage and the other has a switch to the hi temp alarm.

Maybe they could replace the butterfly valve, but I not to sure if they have the height clearance for a ball valve unless it was installed on a 90 elbow.  Will have to look at that.

[John Langford]

I don't have a butterfly valve on my thermostat housing. Just the sender and switch connections. The picture of the engine in the manual shows a petcock but it ain't there and there is no tapped fitting to thread one into.

[Ron Hill]

John : Strange that you don't have a petcock, but don't feel bad because I never used mine on the old engine in 22 years.  I always used a "HandyBoy" PAR pump to clear(suck) the bubbles out of the water heater. 
I'd guess I changed my internal coolant 8-10 times in that 22 yr. period.

If you ever change the thermostate, that would be the time to drill and tap the top of your thermostate housing for a petcock.  A thought

[Ron Hill]

John : Look at your parts book again.  My manual for the M35B engine (dated Dec.2001) shows 3 ports on the thermostat housing.  All three ports come off of the sides and not the top.  One for the temp sender, one for the temp switch(alarm) and one for the petcock - which is in the front.