4BY2 Overheating - is it the thermostat?

[captstu]

Hi, for the past 2+ weeks my 2010 Ranger R-25's Yanmar 4BY2 has been overheating after running for 5 minutes at 3200 RPM.

At 2000 RPM it runs OK.

The domestic hot water is producing ample very hot water.

Today, she was returned to me after the mechanic removed, cleaned, and pressure tested the heat exchanger - no trouble found. They also changed all the hoses related to the heat exchanger.

I capped off the cabin "bus" heater - although there was no signs of a leak. I also tightened the hose clamps on the domestic hot water heater - again, no signs of a leak.

After running the boat at low speed and topping off the coolant, I ran it at 3200 rpm for 5 minutes before the overheat alarm went off. When the engine cooled, it was over 1 gallon low on coolant and the overflow bottle was full - indicating, to me, that while coolant was lost, none was "sucked" back in as the engine cooled.

I installed a T in the "bus" heater line and brought the engine to 15 psi. There was no visible leak and the 15 psi held for 30 minutes.

There is ample sea water flow thru the heat exchanger and the exit water measures 105 degrees F. Once I added coolant, it was cool to the touch indicating, maybe, a block in the coolant lines???

The mechanics suggest changing the thermostat and inspecting/changing the raw water circulation pump.

Any idea what to do now?

 

[scross]

Stuart,
I understand your coolant loss problem is very different than our low coolant problem. We also suspected a bad thermostat before finding the real problem.
At low rpm our boat would stay stable at about 200-205 degrees which is the temp the thermostat is suppose to be wide open. It would only go above 205 if we went above about 2,000 rpm. The fact that the temps heated up after starting and then stayed stable at the 205 degree full open thermostat temp with low rpm told all the “experts” we talked to that it was not the thermostat that was causing the problem.
Hope this info helps....
Good luck!
PS: Our overflow bottle stayed full the entire 4 days we were having our low coolant problem. The big air bubble at the top of the cooling system had no where to go, and expanded when hot, forcing even more coolant back into the overflow tank rather than letting the coolant from the overflow tank move back into the coolant system. Any possibility that the impossible to reach cap at the top is faulty and letting air into but not out of your cooling system?

 

[captstu]

Al and Vicki

I was able to get the Cap off the heat exchanger to add the extra gallon of water after I ran the engine 3200 and overheated.

I also was able to check the lines to the domestic hot water heater and cabin heater and they both had water in them after out of the gallon of water.

I do not think it is the thermostat for two reasons:

One. Where were all the water go? Assuming thermostat is not opening when the system got up to 220 degrees, enough to trip the overheat alarm, but likely not enough to boil the water since there was antifreeze in the water and the pressure was at 15 psi.

Two. When a thermostat fails typically the temperature heats up fairly evenly from room temperature to boiling. In this case the temperature heat it evenly to about 205° And then stopped heating further for five minutes. After five minutes the temperature rapidly climbed from 205° until the over temperature alarm went off. At that point I shut the engine down and let it cool. After two minutes I restart the engine and it was down under 200. This leads me to believe there is a blockage in the coolant line somewhere leading to the heat exchanger?

Tomorrow I will fill the system leave the radiator cap off and I had all the engine until it comes up you’re running temperature. At that point I will physically measure the temperature of the coolant where the cat would’ve gone. Hopefully since the engine is it running temperature the excess heat is being dumped into the heat exchanger to be dissipated in the salt water.

My original guess is that the heating changer was leaking, however the shop test of the heat exchanger and I presume make sure each of the copper tubes inside was clear and flowing water although I don’t know this for sure. I do know that the heat exchanger was returned to me in shiny bright Brand new condition with all of the battle parts that are not painted looking brand new.

Hopefully you’ll find your legs and hopefully it is the ddomestic hot water heater. It is fairly easy to remove the lines for the domestic hot water heater and the cabin heater and bridge the field line from the pump directly to the return line on the port side of the engine all that is needed is a three-quarter inch barb elbow. You might give that a try?

Thanks for the ideas. It is fairly easy to remove the lines for the domestic hot water heater and the cabin heater and bridge the field line from the pump directly to the return line on the port side of the engine all that is needed is a three-quarter inch barb elbow. You might give that a try?

Thanks for the ideas. /Stu

 

[knotflying]

After running the boat at low speed and topping off the coolant, I ran it at 3200 rpm for 5 minutes before the overheat alarm went off. When the engine cooled, it was over 1 gallon low on coolant and the overflow bottle was full - indicating, to me, that while coolant was lost, none was "sucked" back in as the engine cooled.
Any idea what to do now?

Just a thought, If there is a leak somewhere then it may be possible that the vacuum caused when cooling down is being neutralized via the leak opening rather than being siphoned back from the overflow tank and that is why the tank is remaining full.

You say there is no antifreeze in your bilge water. Get an antifreeze detection kit http://chemsee-foods.com/antifreeze-detection. Suck your bilge dry, remove the fuse from the bilge pump, go for a run and then test the water in the bilge. It won't find your leak, but it will prove that the leak is outside the engine. Loosing as much antifreeze as you do and starting out with a dry bilge, I would think you should detect the antifreeze.

 

[captstu]

Good idea about turning off the bilge pump.

I filled the heat exchanger last night, it was 3 qt low this morning, maybe air spaces filling.

I’m beginning to think I have two problems. The overheating is looking more and more like a thermostat issue. Today I took off the heat exchangercap, filled the heat exchanger to the top, and ran the engine for 90 minutes.

The engine came up to 165° on the gauge and about 160 measured with My infrared thermometer. The water in the heat exchanger did not warm up at all, so I’m thinking that no coolant was being interchange between the engine and the heat exchanger.

During the test the heat exchanger cap was off, there were no bubbles visible on the water, and the level did not change once the engine got up to temperature and small amount overflow because expansion.

Tomorrow the thermostat comes out, Another tough job. I am always helpful.

Thanks for the suggestion

 

[scross]

Stuart,
Not sure I understood your last post.
At the risk of sounding like a complete idiot, let me explain how I think the thermostat should be working. When the engine is cold the thermostat is closed. It doesn’t start opening until about 190 degrees or so. At 160 degrees, the thermostat would would be closed if working properly. The coolant in the heat exchanger would not be getting warm because the thermostat allowing flow to the engine section is closed.
At about 190 degrees, the thermostat starts to open allowing flow of coolant between the heat exchanger area and the coolant area of the engine. Above 190 degrees the coolant in the heat exchanger is warming up. At 205 degrees the thermostat is fully opened allowing for full mixture of the coolant in both the heat exchanger and the engine areas.
If the thermostat is stuck open then the coolant in the heat exchanger would start to warm up even at low temps due to mixing. Based on your description at 160 degrees it doesn’t seem that the thermostat is stuck open.
If the thermostat is stuck closed then the engine quickly overheats but the coolant in the heat exchanger area still stays at a reasonable temperature because there is no mixing. From your prior posts i thought you were getting both overheating of the engine and very high temps in the coolant in the heat exchanger area. If so, then it sounds like the thermostat is opening at high temps.
Am I misunderstanding the situation?

 

[Levitation]

If you have a blown head gasket it would answer most of your symptoms.
Because we have water cooled exhaust we will not see the coolant going out the exhaust as steam.
A blown head gasket does not always put bubbles in the coolant nor coolant in the oil - usually one or both are present but there are exceptions.
At this point I am rooting for it to be a thermostat or a water pump so that the solution is easy and inexpensive. Let us know.

 

[knotflying]

Stuart,

In case you do not know, the thermostat is under the heat exchanger in the elbow. You need a mirror and good feel and patience to do this. The manual shows the thermostat in the engine coolant pump, where it normally is, but that is not the case. At least this was the situation on my 4by2-180. Also, removing and reinstalling the t-stat from the elbow is a two man job. I wrote a thread on this and also have pictures of my thermostat removal. The thermostat has to be compressed and fitted under two nibs in the elbow. Thermostats going bad is an unusual occurrence. My problem was I was running too cool. The Thermostat actually popped out of the seat and was therefore allowing fluid to flow freely.

 

[captstu]

Denny-O:

Still thinking about the head gasket. There is no water in the oil and no steam blowing out the exhaust. Most of the water is "lost" in a single glob of about a gallon - last time I filled it to the top and the next morning it was 3+ quarts low without running the engine. I checked the exhaust manifold inspection port under the heat exchanger, it was dry and showed no signs of excessive antifreeze.

Knot: The manual says the thermostat is bolted to the coolant pump on the starboard side of the engine and connected to the hose that goes to the heat exchanger and a second hose that goes to the domestic hot water heater. Both hoses area as the manual pictures. The heat exchanger was off the boat for cleaning and testing.

Would the thermostat as you describe be in one of the hoses that came off during the heat exchanger cleaning? I would think so?????

Anyway, today the assembly behind the metal tube that carries the turbocharger air from the charge cooler to the intake manifold comes off and the water pump and the thing I think is the thermostat come off - assuming the gaskets ordered arrived late yesterday.

The parts "look" like a thermostat and match the book's description. Since the hoses I know about have been replaced, I'm not sure what hose you are describing to contain the thermostat????

I'm especially curious since the heater hose comes off the box and the heater is no longer getting any heat?????

It is starting to look like the recirculation pump isn't moving any cooling water.

Yesterday's test brought the engine to running temp and no heat was detected (IR thermostat= 84.9 degrees) in either the hoses to the heat exchanger or the hot water hoses.

I'm sure I'm missing something obvious - but the combination of water loss and overheat is really confusing to me.

thanks for the thoughts!

 

[BB marine]

Stuart, I have followed your issue and differently feel your pain. Chasing an over heat with a loss of coolant in a boat can be a challenge. There are two components of the cooling system as you know. Raw water cooling and closed cooling. One system works with the other. Raw water is not as simple as seeing good water flow. The small high rpm diesels that we have in our Rangers and Cuts have small exchangers that are properly sized for proper water flow going thru them. Any loss of flow reduces the efficiency of the exchanger. The heat sink effects are reduced and the coolant temperature goes up. On larger exchangers pressure gauges are installed at each end of the exchangers and pressure drop is measured across the exchangers to determine if there is a restriction. In many cases the water flow is not a measurable amount. Water going in comes out. Pressure is the tell tail. This type of troubleshooting is hard to do on our boats. A service technician has to have a plan. Make sure the raw water system is complete. This would be inspect each component of the system. Inspect for no restriction in the system and confirm the pump is preforming to manufactures specs. Testing the pump for gallons per minute . If the complete raw water system checks out. Now the trouble shooting goes to the closed cool system, Circulation of coolant. culprits could be circulation pump, thermostat, hose restriction, internal blockage and loss of coolant. Internal leak is usually the easier trouble shoot, there is evidence of water( antifreeze) in the crank case. Not always though, a crack in the cylinder head that open as the engine heats up from expansion can be expelled with exhaust. If the leak is large enough evidence of white smoke will be noticed exiting the exhaust. Not always. Another internal leak is a crack in the exhaust port the anti freeze will not be in the combustion chamber so there really is no additional smoke it mixes with exhaust. A crack in the exhaust manifold will also leak anti freeze leaving very little trace especially if it is a crack that opens up from heat. If your circulation pump is bad or the thermostats is not functioning properly this could cause the over heat but not loss of antifreeze internally. It could cause an external loss and you would see evidence of this loss. As I have said in a previous post sometimes one problem starts another problem. An over heat from the raw water system being ineffective cause an over heat which can cause an internal crack ,o-ring or gasket failure. An over heat from an closed cooling component can do the same thing. If it was me I would start from point A and work thru the whole system and check off each component until you get to point H,I J,or K. The problem is there and you seem persistent you will find it Good luck.

 

[captstu]

BB, thanks for the comments.

The heat exchanger and all hoses were pulled, cleaned and pressure tested.

The coolant temp in the heater peaked at 94 degrees with the cap off and the engine above 170 degrees.

This makes me think the thermostat is completely clogged or the recirculating coolant pump isn’t pumping.

Gaskets are ordered to pull and inspect both.

The leak, I believe, is another issue. It is getting worse! So it should be easier to find. Engine lost about a gallon overnight while cold. Some in bilge this time.

Maybe the internal air vents from crankcase to heat exchanger are clogged. Any idea how to test these air vents?

Thanks for the thoughts.

 

[Scottfree]

I like to blame cheap parts first. I have had rad caps be the source of steam leaks at the engine running temperatures. Even though the coolant is not at boiling point it will still boil off vapor resulting in coolant loss. They are rated for temperature and pressure so buy the correct one. Also if your changing the thermostat there are the cheap ones and high flow ones. Not sure which one you would have but I would look for the high flow version.

Good Luck, Leon

 

[captstu]

Leon,

I tested the cap by pressurizing the engine by pumping air into the heater hoses via a T. It held 15 psi for 1 hour. Yanmar requires a 20psi cap so I ordered a new one.

The last test was with the cap removed so no pressure built. No bubbles came out of the opening and the coolant did not heat.

Pump. Thermostat. Probably not the cap.

Thank for the the note.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

"Knot: The manual says the thermostat is bolted to the coolant pump on the starboard side of the engine and connected to the hose that goes to the heat exchanger and a second hose that goes to the domestic hot water heater. Both hoses area as the manual pictures. The heat exchanger was off the boat for cleaning and testing."

Stu,

Here is a picture from my album of the thermostat. Like I said, mine was under the heat exchanger in an elbow bolted to the bottom. When I opened up the water pump as you describe it was not there. So pick your poison and hope for the best. You have a 50/50 chance of picking the right spot. Take a look at my album pictures. I have a few potos of it.

 

[captstu]

Strange about the thermostat position?? The hose your picture on the bottom of the heat exchanger was removed and replaced when the heat exchanger was cleaned and tested.

Still waiting for parts, but I’m betting the thermostat is in the assembly that is bolted to the recirculating water pump. Is there any chance yours was pushed out of the normal place and down into the hose where photograph shows?

 

[captstu]

Stu,

Here is a picture from my album of the thermostat. Like I said, mine was under the heat exchanger in an elbow bolted to the bottom. [

I can visualize the spot from your photos, but can’t picture the bolt
Holes shown in the photos. That hose is clamped to the aft bottom of the heat exchanger on my boat. Can you squeeze the bottom of the hose without removing the heat exchanger? I’m trying to see if the thermostat fell out of its mount and clogged in the hose???

How is the metal tube from the charge air cooler to the intake manifold attached to the charge air cooler?


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

Strange about the thermostat position?? The hose your picture on the bottom of the heat exchanger was removed and replaced when the heat exchanger was cleaned and tested.

Still waiting for parts, but I’m betting the thermostat is in the assembly that is bolted to the recirculating water pump. Is there any chance yours was pushed out of the normal place and down into the hose where photograph shows?

Absolutely not. No way it could have traveled. Besides the elbow is designed to receive the thermostat. I do seem to remember that the tech I spoke to said that the thermostat location was changed, so maybe yours is an older version with it still located by the pump. It is easier to get at that then the elbow assembly.

 

[captstu]

Thank you. I’m trying to figure how get the air pipe off the charge cooler without taking the heat exchanger off again.

Maybe I’ll just get a canoe.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796