Overheating Issue

[BlueWhale]

"Single-action thermostats also require a method of controlling the flow within the bypass loop in order to provide the necessary flow through the block and head to enable the thermostat to regulate temperature within normal range. If you do not already have a valve in your bypass loop, you can find one in our online catalog with a product number of CSOT_01_61. "
From the online catalog.

What T-stat did you install?
If you used the T from MMI you must have a bypass unless you just plugged one side of the T. Check and make sure you do not have a bypass as stated in post #4. If you do have the bypass and it does not have a valve that could be your issue.
When cold the T-stat is closed. With out a restriction in the bypass all water goes thru the bypass and passes over the T-stat. This may keep the T-stat cold and it never begins to open. The engine gets hot even though you have full flow out the exhaust because no or very little water is passing thru the block.
I would try the suggestion in post #8 and close/restrict the bypass.

Dan S/V Marian Claire

I now understand the flow of water in the cooling system and I do have a bypass. Working on the suggestions in #8 in the morning.

Thanks

[BlueWhale]

The late model engine will have a hose from the water pump to the T fitting on the side plate. And another hose from the T fitting to the thermostat housing. This is the "bypass" hose.* It allows water to flow around the engine rather than through the engine for a quicker warm up. When the double action thermostat opens it blocks the bypass at the top of the thermostat housing and the water is forced through the engine. Sometimes the seal inside the housing is imperfect due to corrosion and when the thermostat opens the bypass is not blocked and water flows around the engine by way of the bypass. Having a build up of crud in the engine water passages over the years will will make this situation much worse.
So anyway another thing to try is clamping the bypass hose when the engine starts to over heat. This will force all the cooling water to through the engine not around the engine bypass. If this doesn't help ditch the thermostat and try clamping the bypass again.
I can tell you for sure that in a RWC engine that if you have enough water flowing through the engine (not around the engine through the bypass) your engine will not run hot.

TRUE GRIT

* If your plumbing is any different than this let us know. We will also need a picture or two.

I do in fact have a bypass. Thanks for the explanation of the water flow. I'll be trying your suggestions tomorrow.

[BlueWhale]

There is a reason Moyer Marine sells this bronze replacement:

Hope I won't need it :-)

[JOHN COOKSON]

Water flows through the system fine until the temperature rises and the thermostat closes off diverting the water into the engine. It seems that the blockage is either in the engine itself. Perhaps the bypass hose is bad and collapses when the temperature rises? I'll be on the boat in the morning and check it out.
I do get steam, but only after the temperature begins to rise. At that point there is no water flow either.
Thanks

There is something fishy going on here. It almost sounds as if the new thermostat is stuck in the closed position. Did you buy the new thermostat from Moyer? It is like the thermostat is installed up side down but I don't think this is even possible. In any case I'd follow the advice of others and ditch the thermostat for now until all this gets sorted out.

A couple of comments on the quote.
As the engine temp rises the thermostat should open not "close off" allowing more water to flow through the engine.
A collapsing bypass hose is much like clamping the bypass which will force more water into the engine and result in cooler running.

TRUE GRIT

[Marian Claire]

"I do get steam, but only after the temperature begins to rise. At that point there is no water flow either." From post # 14.
Are you saying that the flow out the exhaust stops when the engine is warm/hot?

Dan S/V Marian Claire

[BlueWhale]

There is something fishy going on here. It almost sounds as if the new thermostat is stuck in the closed position. Did you buy the new thermostat from Moyer? It is like the thermostat is installed up side down but I don't think this is even possible. In any case I'd follow the advice of others and ditch the thermostat for now until all this gets sorted out.

A couple of comments on the quote.
As the engine temp rises the thermostat should open not "close off" allowing more water to flow through the engine.
A collapsing bypass hose is much like clamping the bypass which will force more water into the engine and result in cooler running.

TRUE GRIT

The new thermostat works fine. I purchased it from Moyer and checked both the old and new per Ken in the parts department. No, it cannot go in upside down. Thanks for clarifying the "open" and "closed" position of the thermostat. From my understanding of the water flow in the cooling system from the diagram posted earlier, what appears to be happening is when the thermostat opens water is diverted to the engine by way of the bypass into the water jacket.

Today, I attempted to do the muriatic acid flush but, as I am sure many here are aware, one thing leads to another. Before doing the flush I wanted to check to see if the bypass was collapsing. So, I removed the bypass hose from the thermostat housing and clamped it off. When I turned on the engine water started coming out at some point near the T fitting. I'm not sure if I loosened the clamp and water was coming from the hose or some other point. I had to stop the engine before I could see if water was making it through to the exhaust but I doubt if it did. It seems that the blockage is internal. From my understanding of the water flow diagram if the 90 degree elbow at the manifold were clogged water would not flow whether or not the thermostat was open or closed. So, I removed the alternator and the distributor to get at the water jacket cover (recall I replaced it this spring). After removing the cover the water jacket was filled with gunk. I removed as much as I could by hand. I replaced the cover and installed new hoses on both ends (from the pump and the bypass). I attempted to complete the muriatic flush at that point but was unable to get my timing correct after reinstalling the distributor (I always have trouble finding TDC!!!). After struggling with that, becoming completely frustrated and losing daylight I decided to call it a day. I'll get back to it on Saturday. Hopefully, we'll still have warm weather. I guess I have three questions at this point:

1. Am I correct about the 90 degree elbow and the water flow (I'm going to remove it and clean it out anyway)?
2. If the clog is internal how do I clean that out (remove the head)?
3. I have Moyer's manual for the A4 and have followed his directions for finding TDC and aligning the distributor but can never seem to get it right. Is there some gimmick or trick to getting it right?

Thanks

[BlueWhale]

Hello Everyone,

I could use some help with my overheating issue. Let me give you the full context of the problem and what I've done to try to remedy the situation. Perhaps the collective intelligence of the wonderful folk here can save me some time and frustration. Here goes: Last spring I replaced my water jacket cover adding the brass cap and drilling the diversions hole as directed. Everything ran fine throughout the summer. I took several long cruises with no wind and plenty of motoring. Everything worked fine. Later in the season, admittedly after too much disuse, I began to notice on a few short sails that the temperature was running above my normal 140 - 160. Since, I was only going on short sails and only needed the engine to get me in and out of the slip (I cut the engine ASAP) and off I went, until conditions required me to use the engine under heavy load one night. Needless to say she overheated just as i was approaching my marina requiring me to make an emergency stop at the marina next door. I got a tow over to my slip and hoped i hadn't done major damage to my engine as she wouldn't restart after cooling. When I got a chance to get back to the marina a week or so later she started right away but continued to run hot. So, my first thoughts were something was stuck in the intake. I checked the through hull and cleaned out the strainer. I even had the bottom dived on and cleaned. No success. Since I hadn't changed the impeller in a couple of years I next replaced the impeller. It was fouled. The rubber part had separated from the inner ring and was no longer rotating in the pump. Still no success. Next, I replaced the thermostat. I gave the old one a vinegar bath and tested it in a pot of hot water. It was stuck in the open position (down). When the temperature of the water in the pot rose the underside of the thermostat did not rise. So, I bought a new one and figured that would be it and I would be sailing down the Patapsco River very soon. Well, when I installed the new thermostat on Saturday it still overheated - UGH!!! It was suggested that I work my way down the back end of the cooling system checking hoses for crude, corrosion and clogs. That's next on my agenda. I'm somewhat confused on exactly how the cooling system flows. I know when the temperature reaches 140 degrees the thermostat opens to allow water to pass through to cool the engine? How is it diverted when it is closed? In my situation water passes through the system fine until it has to move through the engine. I'm figuring that there is a blockage in that portion of the cooling system. What is the most common place and cause of such an issue? Is my reasoning sound or is there something in my understanding of how the cooling system operates inaccurate? Is it possible that something is going on with the water jacket replacement from the spring (I surely hope not). I'll be removing hoses and elbow joints in the coming days and checking for blockages. Any advice on this matter would be tremendously appreciated. I really need my sailing therapy!

Thanks

Brian
S/V Rekofa The Blue Whale
1979 C&C34

Finally got back to the boat:

Today, I attempted to do the muriatic acid flush but, as I am sure many here are aware, one thing leads to another. Before doing the flush I wanted to check to see if the bypass was collapsing. So, I removed the bypass hose from the thermostat housing and clamped it off. When I turned on the engine water started coming out at some point near the T fitting. I'm not sure if I loosened the clamp and water was coming from the hose or some other point. I had to stop the engine before I could see if water was making it through to the exhaust but I doubt if it did. It seems that the blockage is internal. From my understanding of the water flow diagram if the 90 degree elbow at the manifold were clogged water would not flow whether or not the thermostat was open or closed. So, I removed the alternator and the distributor to get at the water jacket cover (recall I replaced it this spring). After removing the cover the water jacket was filled with gunk. I removed as much as I could by hand. I replaced the cover and installed new hoses on both ends (from the pump and the bypass). I attempted to complete the muriatic flush at that point but was unable to get my timing correct after reinstalling the distributor (I always have trouble finding TDC!!!). After struggling with that, becoming completely frustrated and losing daylight I decided to call it a day. I'll get back to it on Saturday. Hopefully, we'll still have warm weather. I guess I have three questions at this point:

1. Am I correct about the 90 degree elbow and the water flow (I'm going to remove it and clean it out anyway)?
2. If the clog is internal how do I clean that out (remove the head)?
3. I have Moyer's manual for the A4 and have followed his directions for finding TDC and aligning the distributor but can never seem to get it right. Is there some gimmick or trick to getting it right?

Thanks

[JOHN COOKSON]

is when the thermostat opens water is diverted to the engine by way of the bypass into the water jacket.
. So, I removed the bypass hose from the thermostat housing and clamped it off. When I turned on the engine water started coming out at some point near the T fitting. I'm not sure if I loosened the clamp and water was coming from the hose or some other point. It seems that the blockage is internal.

1. Am I correct about the 90 degree elbow and the water flow (I'm going to remove it and clean it out anyway)?
2. If the clog is internal how do I clean that out (remove the head)?
3. I have Moyer's manual for the A4 and have followed his directions for finding TDC and aligning the distributor but can never seem to get it right. Is there some gimmick or trick to getting it right?
Thanks

1. Once water leaves the water pump it goes through the engine or around the bypass or a bit of each. If you have the original three legged thermostat it is a double action thermostat. It opens to allow water to flow through the engine and at the same time blocks off the bypass. The bypass hose goes to the top of the thermostat housing. When the thermostat opens part of it rams up into the top the housing shutting off the flow through the bypass. As a result the water flows through the engine.
2. If you are getting water out the back of the boat the clog is in the engine somewhere. When you clamped the bypass the water could not go through the bypass or the engine and found the weakest point and spurted out. Try this: Take the temp sending unit out and put a common plumbing nipple in its place (I think it's 3/8") attach a tube to the nipple, aim it into the bilge or cockpit, start the engine and rev it up a bit. This will blow a lot of KRAP out of the water jacket and hopefully the clog with it. Be careful not to damage the exhaust system when you do this because no water will be flowing through it.
3. I don't have my Moyer manual handy so can't be of any help with the timing. If you put #1 at TDC compression before you remove the distributor and don't turn the engine you will always have a reference point to come back to. Also did you mark the distributor before removing it?

You're getting closer.
Happy new year.

TRUE GRIT

[Marian Claire]

More questions.
When you replaced the water jacket cover last spring did you clean out the gunk inside?
Did you experience a soft grounding between the time she ran fine and the time you first noticed higher than normal temps?
If so did you run the engine in an effort to get unstuck?

When you say the impeller was fouled, from post #1, what do you mean? Full of mud?

What type of T-stat did you remove?
What T-stat did you install?
Did the new T-stat need one of the spacer kits?
If so was the spacer also installed?
Does your bypass line have a valve?
When the engine warms up do you still have full flow out the exhaust?

Something happened to start this problem. Changing the impeller did not fix it. Changing the T-stat did not fix it. What if the old T-stat was a double action and the new is single. Then there has to be changes made in the bypass set up for it to work properly. It is likely that the cooling passages are clogged but until we know that everything else is set up properly we are just guessing.

Dan S/V Marian Claire

[hanleyclifford]

1. Once water leaves the water pump it goes through the engine or around the bypass or a bit of each. If you have the original three legged thermostat it is a double action thermostat. It opens to allow water to flow through the engine and at the same time blocks off the bypass. The bypass hose goes to the top of the thermostat housing. When the thermostat opens part of it rams up into the top the housing shutting off the flow through the bypass. As a result the water flows through the engine.
2. If you are getting water out the back of the boat the clog is in the engine somewhere. When you clamped the bypass the water could not go through the bypass or the engine and found the weakest point and spurted out. Try this: Take the temp sending unit out and put a common plumbing nipple in its place (I think it's 3/8") attach a tube to the nipple, aim it into the bilge or cockpit, start the engine and rev it up a bit. This will blow a lot of KRAP out of the water jacket and hopefully the clog with it. Be careful not to damage the exhaust system when you do this because no water will be flowing through it.
3. I don't have my Moyer manual handy so can't be of any help with the timing. If you put #1 at TDC compression before you remove the distributor and don't turn the engine you will always have a reference point to come back to. Also did you mark the distributor before removing it?

You're getting closer.
Happy new year.

TRUE GRIT

This is a solid approach (but the temp sending unit could be tough to remove and could be 1/2" NPT). However I would first clear (and possibly replace with a straight nipple to barb) the manifold discharge. The question will become: does the double acting thermostat actually block off the by pass as indicated?

[JOHN COOKSON]

This is a solid approach (but the temp sending unit could be tough to remove and could be 1/2" NPT). However I would first clear (and possibly replace with a straight nipple to barb) the manifold discharge. The question will become: does the double acting thermostat actually block off the by pass as indicated?

Post # 14: "I do get steam, but only after the temp begins to rise. At that point there is no water flow either".

A possible explanation for this is when the bypass is blocked as the engine heats up and the thermostat opens water can't can't flow through the engine or bypass all goes to hell in a hand basket. I assumed Brian had water flow out the exhaust when the engine was cold, but the water flow out the exhaust stopped when when the engine heated up. Maybe not. If there is no water coming out the exhaust ever then there is for sure a blockage somewhere.

Edits to a previous post: When you remove the sending unit do not use a open end wrench. You will only round the soft brass. I had good luck with a closed end wrench and a hammer.
When you start the engine with the nipple in place clamp the bypass. This will divert all the water into the engine and hopefully through the engine.


TRUE GRIT

[hanleyclifford]

Post # 14: "I do get steam, but only after the temp begins to rise. At that point there is no water flow either".

A possible explanation for this is when the bypass is blocked as the engine heats up and the thermostat opens water can't can't flow through the engine or bypass all goes to hell in a hand basket. I assumed Brian had water flow out the exhaust when the engine was cold, but the water flow out the exhaust stopped when when the engine heated up. Maybe not. If there is no water coming out the exhaust ever then there is for sure a blockage somewhere.

Edits to a previous post: When you remove the sending unit do not use a open end wrench. You will only round the soft brass. I had good luck with a closed end wrench and a hammer.
When you start the engine with the nipple in place clamp the bypass. This will divert all the water into the engine and hopefully through the engine.


TRUE GRIT

Good analysis. If indeed you are getting good water flow out the exhaust while the engine is cold (thermostat in lower position allowing water thru the bypass while sealing off the block), but water stops flowing when the thermostat opens up the passage thru the block but shuts off the bypass, then the manifold discharge is not the culprit. This narrative points squarely to a blockage in the block itself. I concur with John re the temp sending removal. A better method might be to use a six point socket with a breaker bar, but be warned that you may shear the thing off flush with the casting. Have a pipe tap and drill at the ready and a plug or new sender.

[BlueWhale]

More questions.
When you replaced the water jacket cover last spring did you clean out the gunk inside?
Did you experience a soft grounding between the time she ran fine and the time you first noticed higher than normal temps?
If so did you run the engine in an effort to get unstuck?

When you say the impeller was fouled, from post #1, what do you mean? Full of mud?

What type of T-stat did you remove?
What T-stat did you install?
Did the new T-stat need one of the spacer kits?
If so was the spacer also installed?
Does your bypass line have a valve?
When the engine warms up do you still have full flow out the exhaust?

Something happened to start this problem. Changing the impeller did not fix it. Changing the T-stat did not fix it. What if the old T-stat was a double action and the new is single. Then there has to be changes made in the bypass set up for it to work properly. It is likely that the cooling passages are clogged but until we know that everything else is set up properly we are just guessing.

Dan S/V Marian Claire

I cleaned out as much as I could which was very little. It's in a difficult location.
No grinding sound or attempts to get unstuck.
No mud in impeller. The rubber part separated from the inner ring. None of the fins came off.
I replaced the Tstat with the same type (double action, three legs).
No spacer or valve.
Water flows out the exhaust until the temp rises above 180 - then only steam.

[BlueWhale]

Good analysis. If indeed you are getting good water flow out the exhaust while the engine is cold (thermostat in lower position allowing water thru the bypass while sealing off the block), but water stops flowing when the thermostat opens up the passage thru the block but shuts off the bypass, then the manifold discharge is not the culprit. This narrative points squarely to a blockage in the block itself. I concur with John re the temp sending removal. A better method might be to use a six point socket with a breaker bar, but be warned that you may shear the thing off flush with the casting. Have a pipe tap and drill at the ready and a plug or new sender.

I don't like the sound of that. Should I even try the muriatic acid flush?

[ndutton]

Seems clear to me your block/head is clogged. When the temp is low, the double action thermostat allows water through the bypass directly to the manifold. As it warms the thermostat opens the block/head passage and restricts the bypass. Your water flow out the exhaust should lessen (not that it should but I expect yours does). When it reaches 180° the thermostat has fully closed the bypass and fully opened the block/head passage in favor of full block/head flow and since it's clogged there isn't any flow.

At least that's how I see it.

If this is correct, I don't expect an acid flush will help at this stage of occlusion. I think you're looking at a manual mucking out and depending on your sailing area be prepared for stuff as hard as concrete. On my spare engine I went after it with a pneumatic needle scaler, like a mini jack hammer. And expect to remove the head for access to several small passages. Sorry.