Perkins 4236 Strange Overheat Problem

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8 years 9 months ago #1151 by Lee Davis
Perkins 4236 Strange Overheat Problem was created by Lee Davis
Lew-

Have a overheat problem with the Perkins 4236 on my Brewer (Hull #268). Have about 5000 engine hours. My exhaust elbow was getting clogged with mineral deposits, so I just finished a fairly extensive maintenance process where I changed out the exhaust elbow, installed a new exhaust manifold, replaced all hoses, replaced the raw water impeller, installed new belts, installed new thermostat and coolant, and acid washed the heat exchanger. Have gone over both the raw water and fresh water circuits pretty thoroughly. I have excellent raw water output from the exhaust now and the header tank coolant remains at the full level (not losing coolant). When I run the engine under load, engine temp will slowly rise for about 15 minutes until the overtemp alarm sounds (temp indicator shows under 180 degrees). I back off the throttle to idle and let it run for around around a minute or two and then then thermostat will kick in and water temp goes to 160 degrees (currently have a 160 degree thermostat installed) and the overtemp alarm will die out. I can then run the engine for hours at full load and the engine will never show an overheat condition again. But if I turn the engine off and let the engine cool down, the overheat process will occur again until I idle for a couple of minutes, etc. This happens every time.... have duplicated it around 10 times now.

So... it seems like the themostat is not kicking in soon enough to prevent an overtemp alarm. I have tried another 160 degree thermostat- same results. I have monitored the engine temps with an IR themometer. It seems that the rear of the engine is hotter than the front of the engine by 10-20 degrees. I think the overtemp alarm sender is at the rear and the engine temp gauge sender is at the front (not 100% sure of this as I haven't traced out the wiring yet).

Maybe I have air in the freshwater system ? If so, not sure how to check this or bleed it out.
Maybe I have some blockage in the freshwater system ? If so, not sure how to check this and remove the blockage.

Any ideas would be greatly appreciated, Lew.

Thanks,

Lee Davis
S/V Head Out

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8 years 9 months ago #1152 by Robert Slais
Replied by Robert Slais on topic Re:Perkins 4236 Strange Overheat Problem
Hi Lee,
It seems that your thermostat just needs to get in contact with the hot coolant to start it's regulation. Try drilling a 1/16 hole in the thermostat base to allow a tiny bit of coolant to bypass the thermostat. A hole this size will not prevent the thermostat from allowing the Perkins to come up to operating temperature, but would allow sufficient flow of coolant to come in contact with the thermostat itself.
Bob Slais

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8 years 9 months ago #1153 by Lew Streeter
Replied by Lew Streeter on topic Re:Perkins 4236 Strange Overheat Problem
Nice that the problem is not intermittent at least.
Sounds like you have an air bubble in the fresh water side. I would suggest a coolant over flow bottle to give the air a place to go and not come back into the system. Make certain to change the cap also so that you have a seal at the top of the cap so the coolant will go into the bottle. I will usually mount the bottle above the engine in a very convient place to be able to see it and add coolant. If you are using pre mix coolant make sure it is for diesel engines. If you are mixing the coolant yourself use distilled water and never use different colors of coolant with each other as this can lead to a gelling situation
You should be using a 180 degree thermostat to help with getting rid of condensation in the crankcase.
Apparently you have reconnected all of your cooling lines correctly or the condition would never go away. Drilling a very small hole in the thermostat is a good idea in fact some of the Perkins came with that done to their original stat.
Make certain that the stat is installed in the right direction that would be the temp sensor side in the coolant and the cone up.
Lew

PS Great advice Bob

Lew Streeter
Free N Clear
Hull #70

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8 years 9 months ago #1154 by Lee Davis
Replied by Lee Davis on topic Re:Perkins 4236 Strange Overheat Problem
Bob- Thanks for the advice- I'll drill out the hole this weekend and report back. Used to have to do this on an old Dodge pickup I once owned but had completely forgotten about this- it's always fun re-learning those lessons over and over !

Lee
S/V Head Out

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8 years 9 months ago #1155 by Lee Davis
Replied by Lee Davis on topic Re:Perkins 4236 Strange Overheat Problem
Lew- And thanks for your excellent advice, too, Lew. I'll use an SCA based diesel engine coolant when I drill out the hole in the thermostat. I did install a coolant overflow bottle a few years back. I'll let you know how this pans out.

What's the easiest way to flush out the existing coolant in the system so I don't mix the different coolants ?

Lee
S/V Head Out

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8 years 9 months ago #1157 by Lew Streeter
Replied by Lew Streeter on topic Re:Perkins 4236 Strange Overheat Problem
While you have the thermostat out drain the block of coolant and flush out with a hose. Make certain not to just throw the coolant out as it needs to go to a company that can recycle or handle it correctly as coolant is a poison.
Lew

Lew Streeter
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Hull #70

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8 years 9 months ago #1159 by Lee Davis
Replied by Lee Davis on topic Re:Perkins 4236 Strange Overheat Problem
Thanks, again, Lew. Not 100% sure how to make sure the block is completely drained. Is there a water drain plug on the block somewhere ? Probably if I lived in a cold climate and had to winterize my boat I would know this ! I also have a water heater in the circuit (under the chart table across from the engine room).

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8 years 9 months ago #1161 by John Meskauskas
Replied by John Meskauskas on topic Re:Perkins 4236 Strange Overheat Problem
Guys, I have a Perkins 4.236 in hull #2. I rebuilt the engine and t does the same thing. I checked the engine with an IR thermometer and the rear is a bit warmer than the front. The thermostat is all the way in the front, the meter sender in the rear . My engine does not have an overheat sensor but the temp gauge slowly goes to about 210 and stays there. After about 5 minutes the thermostat opens, the temp comes down to 180 and stays there. I like the idea of drilling the thermostat but wouldn't go to any further trouble to resolve this. It has been completely predictable in its response over about 700 miles of operation.

John Meskauskas S/V Laume II

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8 years 9 months ago #1162 by Lew Streeter
Replied by Lew Streeter on topic Re:Perkins 4236 Strange Overheat Problem
Yes there is a plug on the side of the block some have a petcock others just a pipe plug. As for the heater just disconnect the hoses at the engine and have them lower than the heater and they will drain it out. Your maintenance manual should show you where the plug is. If you don't have a manual you should get one, possibly one of the members has one in electronic form that you might be able to use.
Lew

Lew Streeter
Free N Clear
Hull #70

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8 years 9 months ago #1166 by Lee Davis
Replied by Lee Davis on topic Re:Perkins 4236 Strange Overheat Problem
Thanks, again, Lew. Have a Perkins maintenance manual but the locator picture for the 4236 is terrible- one picture shows a drain plug somewhere on the starboard side (looks like under the rear of the heat exchanger) and one shows a drain plug on the rear of the engine near the oil cooler. As neither location is very accessible I'll have to do some gymnastics but I'll find it !

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8 years 9 months ago #1167 by Lee Davis
Replied by Lee Davis on topic Re:Perkins 4236 Strange Overheat Problem
Thanks, John- sounds like we have the same issue. I am going to try drilling a hole in the thermostat and I'll let everyone know the results. I am hesitant to just let this continue, as is, as the overtemp alarm will eventually drive me crazy- I could disconnect it but I think an overtemp alarm is a good idea on a diesel, just in case.

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