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Old 07-07-2020, 11:31 AM   #1
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CAT 3306 overheating

I have done a barnacle flush on the sea water circuit using Rydlyme, over the weekend.
The flush was successful. The idle temp went down. However, the engine still overheats at cruising rpm, which is 1500.
At 700 rpm idle, the temp is steady at 160F. In reverse gear, idle rpm 700, the temp is 175-180 and steady. When I put it in neutral and go up with rpm, it is 180 at 1000 and 1200, but at 1500 it overheats to 210/220.
At this point I ran it on idle for 5 minutes to cool it down and turned it off and started again. It was 180 at idle rpm. I am afraid to take her out and have the engine overheating, while cruising. Your opinion? Thanks
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Old 07-07-2020, 12:27 PM   #2
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You have addressed just one of several possible causes of engine overheating. Others, in no particular order, are:

1. Sea water flow is reduced due to a restriction in the suction side of the pump: collapsed hose insides, barnacle fouling of the hull inlet, strainer plugged with sea weed, etc.

2. Impeller is bad or pump body is worn reducing flow.

3. Main heat exchanger is plugged with old zincs or marine growth.

4. Injection elbow is plugged with scale reducing flow.

5. Antifreeze coolant side is fouled.

6. Coolant side pump is bad

7. Coolant side thermostat is stuck closed

The list goes on. But don't just start tearing things apart and cleaning or replacing stuff, although that may be a good idea for an old engine with neglected maintenance. Most of these can be ruled in or out with intelligent diagnostics with limited tools like an IR gun.

David
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Old 07-07-2020, 12:35 PM   #3
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Originally Posted by DavidM View Post

The list goes on. But don't just start tearing things apart and cleaning or replacing stuff, although that may be a good idea for an old engine with neglected maintenance. Most of these can be ruled in or out with intelligent diagnostics with limited tools like an IR gun.

David
Thanks David.

I have a longer history about this problem on this other thread:
https://www.trawlerforum.com/forums/...tml#post897230

I started a new one, because this time the issue might not be the sea water circuit. I have replaced the thermostat, the temp sender, and the sea water pump. I did the barnacle flush on the sea water circuit.

It seems the problem is with the coolant flow. It is enough for low rpm, but at high rpm, like cruising speed, it is not.
I am looking for ideas, how to narrow it down? Belts, or water pump?
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Old 07-07-2020, 01:11 PM   #4
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I fixed overheat problems in a number of engines with a similar history of work done. Often the need to flush the coolant side gets overlooked. When the coolant gets old, the anti-rust properties are lost. Rust can form on the water jackets and passages in the block and head. It acts as insulation. So less heat is transferred from the engine to the coolant until the heat rise is uncontrollable. Rydlyme also dissolves rust. It's a quick, easy operation to try before throwing more parts at the engine. It's worked for me many times. Since the engine doesn't overheat at idle, running a couple hours at 160įF will speed up the cleaning.
One more thought, too high of a antifreeze mix doesn't transfer heat as well as water. Using 100% antifreeze can lead to overheating.
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Old 07-07-2020, 01:30 PM   #5
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I fixed overheat problems in a number of engines with a similar history of work done. .
Lepke

If I understand you correctly, you would do a Rydlyme flush on the coolant circuit, as well? Am I correct?

Do you have any advice, how to collect the coolant safely, without letting it into the bilge? I am on the hook full time and it is difficult to maintain a dry bilge.
Thanks.
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Old 07-07-2020, 01:38 PM   #6
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. Rust can form on the water jackets and passages in the block and head. It acts as insulation. So less heat is transferred from the engine to the coolant until the heat rise is uncontrollable.
Do you see any rust inside the coolant pipe on this photo?
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Old 07-08-2020, 12:26 PM   #7
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Originally Posted by Lepke View Post
I fixed overheat problems in a number of engines with a similar history of work done. Often the need to flush the coolant side gets overlooked.
Lepke
Do you know where the drain plug is for the coolant on a 3306? Is there one on the block, or somewhere else? I cannot figure it out from the manual.
Thanks.
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Old 07-08-2020, 12:47 PM   #8
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I don't know the 3306 very well. Since you have been into the coolant side is it possible for the circ water pump to be full of air? Most engines are self bleeding but some are not.

Belt driven or gear driven circ pump? Seen pumps where impeller slipped off shaft. Looked all normal, but would not pump.

With engine warmed up to where tstat starts to open, you should be able to sense coolant flow beginning. Pipes leading to HX should warm up, HX should warm up a bit on one end.

If the HX is fouled on either side (or both), coolant at exit will be hot where it leads to circ pump suction.

Usually the exhaust manifold and turbo (if water cooled) are on a separate flow path that does not go through the tstat and HX. So as engine warms up those two things should warm up uniformly and their plumbing should warm up indicating flow. If manifold warms up but plumbing stays cool that means no flow.

That it is overheating at such low power setting makes me want to verify the circ pump is doing its thing.
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Old 07-08-2020, 02:19 PM   #9
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CAT 3306 overheating

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Originally Posted by Ski in NC View Post
That it is overheating at such low power setting makes me want to verify the circ pump is doing its thing.

I suspect it is gear driven circulation pump. I looked at it this morning and I donít see a belt going to the pump. I suspect I know which is the circulation pump, but I was not sure. I took some photos. I see a plug at the bottom of it, so it could be the draining spot for it.
I really want to descale the coolant system, before I do further troubleshooting.
The belts you see on the photos are the alternator one on the left and the hydraulic pump on the right. The water pump must be the one above the hydraulic pump and part of the block. That is my guess.
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Old 07-08-2020, 03:40 PM   #10
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Quote:
Originally Posted by LeoKa View Post
Lepke

If I understand you correctly, you would do a Rydlyme flush on the coolant circuit, as well? Am I correct?

Do you have any advice, how to collect the coolant safely, without letting it into the bilge? I am on the hook full time and it is difficult to maintain a dry bilge.
Thanks.
Yes, I'd use Rydlyme on the coolant side. It dissolves rust. Rydlyme is biodegradable so I pump it over the side. On my engines, I installed a small valve on the block drains so I can connect a hose, circulate, drain, etc. On the Detroits, before the block drain valve, I have a builtin pan under the engines and drain the antifreeze into that and then pump into a bucket. Now I just run a hose to a bucket. If you're fast when the engine is cold, you can pull the plug and install the valve without a big loss of coolant.

When I was a fisherman, in warmer waters, many didn't use antifreeze, just an anti-rust additive and water. Those that let the anti-rust additive get old had overheat problems and had to do a coolant flush. Just like maintenance on a car, the coolant side needs a flush at times.


It sounds like you've done all the common fixes for overheat in the raw water side. If you have a good thermostat, good exhaust water flow, and recent flush, it has to be a coolant side problem. But, since the idle temps went to normal after the flush, but not cruising, it's remotely possible you need an additional raw water flush.
Raw water flow is important. I have seen barnacle and mussel growth inside plumbing close to the seacock. Also in a ship used seasonally, I had mussels in the plumbing, die when the ship was laid up in fresh water, and then come loose and plug the strainer the first time the engine was started after layup. Since that experience I've always added a way to force out the salt water with fresh and close the seacock when laying up.
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Old 07-08-2020, 04:19 PM   #11
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Leo
Two questions
--When was the last time the engine and transmission coolers were removed, cleaned, inspected and pressure checked?
--Has this engine ever run at full rated RPMs without overheating?
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Old 07-08-2020, 04:36 PM   #12
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Leo
Two questions
--When was the last time the engine and transmission coolers were removed, cleaned, inspected and pressure checked?
--Has this engine ever run at full rated RPMs without overheating?
I have removed the transmission exchanger 2 weeks ago and could not see any blocking stuff there. Just last week, I did the Rydlyme flush, when the mix was sitting all night in the sea water circuit and pushed out in the morning. This included all the elements of the sea water section. The engine heat exchanger has not been removed, but there was healthy outflow on the sea water side. The flow increased significantly, when the I ran the engine at higher rpm.

I did the max rpm couple months ago on a weekend trip. There was no overheating at that time.

The coolant was replaced in 2018.
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Old 07-08-2020, 04:44 PM   #13
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CAT 3306 overheating

Quote:
Originally Posted by Ski in NC View Post

If the HX is fouled on either side (or both), coolant at exit will be hot where it leads to circ pump suction..


The pipe elbow, which connects to the engine at the thermostat, gets really hot. That is the spot, where the alarm switch sits, so it triggers the alarm. There is a 30-40F difference between the HX side of this elbow and the other end, at the thermostat connection. This elbow has a small hose section clamped in the middle, but nothing else. My guess is, there is little flow, or the thermostat does not open enough, and the coolant accumulates at this turn, making the elbow very hot.

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Old 07-08-2020, 05:45 PM   #14
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I don't know the 3306, but I was able to find a link to a CAT 3306 water pump:

https://huace-parts.com/product/cate...8002-for-sale/

It looks like the item you identified earlier in the thread and also looks to be gear driven. Possibly it's impeller has worn off or come loose on it's shaft?

Also keep in mind that even though you put a new thermostat on does not mean it's working correctly, a brand new part can be bad as well. Easy to test, drop it in a coffee cup full of boiling water and see if it opens.
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Old 07-08-2020, 05:54 PM   #15
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Thinking about it some more, you say that the elbow gets hot on the side that's attached to the engine, but on the other side of the hose on the heat exchanger it's 30-40 degrees cooler. Sure sounds like the thermostat is not opening. The elbow bolted to the engine is probably getting hot just because it's bolted to the engine, and the heat exchanger is thermally isolated by the rubber hose, if the coolant was flowing it would seem like the elbow attached to it would heat up also. Does the heat exchanger heat up at all, or does it stay cool?
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Old 07-08-2020, 07:52 PM   #16
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T Does the heat exchanger heat up at all, or does it stay cool?

Yes it does heat up. You can on the photos that I have measured around 150-160F inside, sticking the gauge into the coolant. The housing of the exchanger is over 100F.
The elbow in question has a bit large diameter than the thermostat. Still, the flow should be sufficient enough to keep the elbow within normal temps. The alarm switch sits right next to it and it should trigger at 195F, which it does. It should not go that high. There is not enough coolant flow. Be it the thermostat or the water pump. I need test both. I have a quote for the pump around $190.
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Old 07-13-2020, 11:52 PM   #17
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I am still waiting for the water pump and gasket kit. Hopefully I can do the swap and cleaning of the coolant section this weekend.

I took the boat out yesterday for a spin, but I did not get far. After about 20 idle speed, the temp went up to 180-190F. I disconnected the alarm switch and continued. It was stabile for a while, so I pushed the rpm higher. At 1000-1200 it was still around 200, but when I raised it to 1500 rpm the coolant boiled and the temp jumped to 240. I had to shut it down for a while. After restart, I moved very slowly back to my base. It just cannot handle higher rpm.
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Old 07-14-2020, 06:21 AM   #18
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Not a good idea to run the engine under load until you get this sorted. Good way to trash the engine.
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Old 07-14-2020, 07:31 AM   #19
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Not a good idea to run the engine under load until you get this sorted. Good way to trash the engine.
+1

Ignore those that are saying your gauges or temperature sensors are at fault until you fix problem. Years ago I worked at a place that had a dozen or so 3306s. The heads were very susceptible to cracking with minor overheats.
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Old 07-14-2020, 11:29 AM   #20
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+1
Ignore those that are saying your gauges or temperature sensors are at fault until you fix problem. Years ago I worked at a place that had a dozen or so 3306s. The heads were very susceptible to cracking with minor overheats.
I hope it did not happen this time. The run was less then a mile and lasted about 20 minutes. Most of the time I was moving with idle speed, with no overheating to extreme temps.
I wanted to see, if the overheating at 1500 rpm will happen underway, too? It happened before, while running in neutral, hooked to my buoy.
I watched the gauge closely and once the needle started to move up fast, I shut down the engine. Few minutes later I started it again, but ran it only on idle at 700 rpm and it cooled down to 180F and stayed there.

What is the best way to see, if there was any damage to the head?
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