4BY2 Overheating - can the thermostat be removed?

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4BY2 Overheating - can the thermostat be removed?

Postby captstu on Wed May 23, 2018 8:39 am

My 2010 R25's 4BY2 engine is overheating and leaking coolant.

We tried pressure testing, removing/cleaning/testing the heat exchanger, and several other things - now it is time to replace the thermostat.

The thermostat assembly is either unavailable or a long time (week +) in coming - this is a frequent problem with Yanmar parts for this engine.

Question: Can I remove the thermostat assembly, remove the thermostat from the assembly and replace the assembly, allowing a full flow of coolant from the engine to the heat exchanger?

Thanks /Stu
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby NorthernFocus on Wed May 23, 2018 8:59 am

Down south where you are you can probably get away with it due to the warm water. Based on the history of the problem you're having I'd say you have little to lose. "Back in t he day" when dealing with an engine overheat problem that was one of the first things we'd do.

Also tstats are a commodity item. If removing it resolves your overheat issue you can take it to a NAPA store and they might be able to match it for you.
Dan

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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Wed May 23, 2018 9:55 am

Dan,

According the the parts list, the thermostat and assembly are a single assembly on the $BY series -- and I can't get the part, or at least have not yet.

I know about running without a thermostat - should be OK for a short time.

So, the question remains,

Can I get the Thermostat out of the thermostat assembly on the 4VY2?
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby Brian B on Wed May 23, 2018 11:15 am

Stu,
I assisted Knotflying on the Tstat replacement on his 4BY2 180, same block as your 150. As he mentioned in a previous thread the T stat could be in one of two places. It is a bear of a job. I’d wait for the correct part to have on hand. No sense in going through all that work twice. You should speak with Knotflying (AKA Mike) directly.
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby NorthernFocus on Wed May 23, 2018 11:50 am

captstu wrote:...So, the question remains,

Can I get the Thermostat out of the thermostat assembly on the 4VY2?

Sorry, Stu. I missed the crux of the question there. Without knowledge of that engine I should have refrained from commenting.
Dan

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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Wed May 23, 2018 12:46 pm

Dan, No problem - threads are hard to follow and I appreciate the help.

I've spoken to Mike - not 100% sure my thermostat is where his is, but it might be. It is truly difficult to access, far beyond my older hands - and I have a mechanic who is working the problem.

But, I have both an overheat and a leak - not sure they are the same problems - and parts are nearly unobtainable here in S. Florida. The boat has been down for a month with no idea of what is truly broken.

so, I was thinking of a hammer and chisel removal of the t'stat to see if at least the overheat goes away. I think I can do that by loosening the turbo-charger air tube to the intake manifold and taking out the 4 t'stat T'4 bolts to gain access to the t'stat itself.

Some hammering and cutting I thought I could make a hole in the existing t'stat to let some water flow - none is entering the heat exchanger at any temperature now. If this circumvents the problem, I can run the boat cool until the mechanic (an authorized Yanmar dealer) can locate a new t'stat -- or if the problem persists, at least go on to the next step, removal of the engine.

I'm trying to locate a non-Yanmar engine for a replacement because I just can't keep an engine running without a source of parts and what I think of as second level support.

Thanks again - don't hesitate to throw out ideas, please!
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby knotflying on Thu May 24, 2018 7:04 am

Stu,
The T-stat is a BMW part. We can do one of two things. I have a spare ( the old one I replaced, but it is a good one) a) If there is a BMW part number on it I will send you the info. b) I can send it to you and when you get yours send it to me. From what I could tell in my adventure the thermostat can just be removed in either location and then reassembled.
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby crowleykirk on Thu May 24, 2018 10:03 am

I'm new to the forum but would like to comment here. My past background, many moons ago we were the Ford Lehman dealer for Grand Banks and others in Newport Beach CA. We were also certified by Cummins, CAT, Onan, Borg Warner and of course Ford. We also worked on Yanmar's, Perkins, John Deer and others. We did not care fo the Yanmar's much, mostly they where in sail boats. Parts were hard to come by and they just seemed to have a lot of issues. No granted, this was back in the 80's and 90's. I know they are solid engines. Here's my comments but please forgive me for I don't know the exact engine you mention here.

The Lehamn's and Yanmar's and all others can suffer from over heating from many causes as you all know. Obviously check your thru hole first, remove the hose from the sea strainer and open the sea cock. You want good flow. Next the raw water pump. The obvious is impeller but make sure the pump is in good shape and not leaking or cavitating as it may be to worn to work properly. If you find a broken impeller you better go find the blades that are missing. We always carried spares pump and impeller. Next keep following the water flow. If you don't use a boat for awhile and they sit in the water corral can grow in your hoses and oil coolers and heat exchangers. Squeeze those hoses, do they make a crunching sound? Pull the hoses off any coolers and look inside. They look like a small heat exchanger. a 1/8 dowel will help with cleaning but if the are bad remove them and soak in miratic acid (pool acid). If they are older than 4 years they should be replaced, give or take. I can tell you many stories on this subject. Like batteries, just replace every 4 years or so. Those zincs can cause a lot of build up in your heat exchangers, clean them every 6 months with the dowel and flush.

Is you overboard discharge normal? Once the raw water side of things is good next would be the engine and fresh water side. Forgive me if you are not raw water cooled. I'm not up to date on the latest and greatest. I will be soon as we are looking at a Ranger, At or NT soon as well.

You can test that thermostat in a pot of hot water and a thermometer to see if it is opening at the correct temp. You can run for awhile without it. If it's really cold you may just get some unburnt fuel out the exhaust, smoke. White.Cold running.

Make sure the hoses are not being restricted and the water pump is not leaking etc... the fresh water side is pretty simple. It's usually the raw water side that is the problem. Of course there are many engine issues that can cause heating but that's another discussion and I'd need to know more about that particular engine etc... When you do an oil change, at least once a year I'd get an oil analysis, same for the tranny. Helps keep on eye on what's going on inside your engine.

If your engine is running smooth and not rough from a bad injector, rings worn etc.... you should be in good shape. If you are having engine noises or rough running and idling well, you have other issues that could be causing the overheat.

Good luck, just start from the beginning of your raw water flow and work your way to the end. I always advised to my customers to carry cruise kits. Always. Keep any spares and especially those you know are difficult to order and get in a timely manner. In which most cases you will not know until you need it... right? But.. just saying... there are certain parts you will replace anyway at some point. I'd buy some of these ahead of time. I'm kinda of a nerd when it comes to this subject. When we boated and when I went with customers we took a lot of spares, even an injector or two. And on one trip we actually used that spare injector. Only time I've seen that.

Hope you get it figured out and back on the water and having a great summer:-)

Kirk
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Thu May 24, 2018 10:42 am

Dan/Mike, The parts came, the thermostat assembly is here --- but there is no thermostat.

So, I must guess mine is where yours was????

No idea of the parts to order, my manual shows the thermostat in the assembly.

Any chance you could e/mail me the page from the parts catalog that describes your engine?

thanks! /Stu@shearwater-sailing.com
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Thu May 24, 2018 10:44 am

knotflying wrote:Stu,
The T-stat is a BMW part. We can do one of two things. I have a spare ( the old one I replaced, but it is a good one) a) If there is a BMW part number on it I will send you the info. b) I can send it to you and when you get yours send it to me. From what I could tell in my adventure the thermostat can just be removed in either location and then reassembled.


Looks like I have a spare also. Where did you get the part number for the one you installed in the hose? It isn't in my book??
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Thu May 24, 2018 5:12 pm

Turns out there are two placers where the 4BY2 can have a thermostat.

The usual place on top of the block is where the service manual tells you to remove and replace it when the t'stat fails.

Knot - and others - have pointed out the second place, not in my service manual but as a small part on Figure 11 of the parts manual, #120650-44570.

We removed the thermostat assembly described in the service manual - there was no thermostat present. We are now trying to remove the other thermostat described above - but have so far not found it! We know it is on the line from the water pump discharge to the heat exchanger raw water input - so it is off with the heat exchanger for the second tine,

When we get this apart, the thermostat goes in the scrap bin - and we re-install the original top-of-the-block thermostat as described in he service manual.

My guess is the new location was chosen to allow more of the engine to heat to reduce the emissions - but, in my case, the primary emission reduction comes from missing two planned trips because the engine won't run.

Question: How to I remove the thermostat located on the exhaust manifold?
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby knotflying on Thu May 24, 2018 5:25 pm

Stu,

I sent you info via your e-mail address with a diagram and how I removed mine. If you get to it getting the new one into the assembly is a two man deal. It has to be compressed and locked in and seated properly. I installed mine back where it was. I had several discussions with various Yanmar techs. I wanted to opt to put the thermostat back in at the easy spot. The answer I got. "Put it where it was"!
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4BY2 Overheating - can the thermostat be removed?

Postby captstu on Thu May 24, 2018 9:10 pm

Did get it out. Plan to put it at the top of the block near the water pump. Is that what you meant, “where it was.”

Thank you. Stu@shearwater-sailing.com
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby knotflying on Fri May 25, 2018 5:23 am

captstu wrote:Did get it out. Plan to put it at the top of the block near the water pump. Is that what you meant, “where it was.”

Thank you. Stu@shearwater-sailing.com

Not in the water pump, back into the elbow.
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Re: 4BY2 Overheating - can the thermostat be removed?

Postby captstu on Fri May 25, 2018 5:50 am

Thank you. The mechanic won’t put the thermostat in the elbow and I can’t.

Massey is saying the boat bottom is dirty and there is air in the coolant.

Still no idea where the leak is!

The coolant in the heat exchanger is not heating so there is a clog, bad thermostat or a bad raw water pump. If the just painted Boat bottom we’re dirty, I think the coolant in the heat exchanger would steam and push coolant into the recovery bottle.

We are just taking off parts with no real idea.

Curious, why put thermostat in elbow, Yanmar said it was done to meet emission rules when engine idles a long time. Is there another reason?


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