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Old 28-04-2013, 16:56   #1
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Perkins 4108 Overheating/Steaming

Bought a 1978 Cal 39 about two years ago, and the engine coolant pump was frozen. The local mechanic changed the pump and it worked okay for docking and short motors. When we began using the motor for over a half hour, we noticed problems.

The temperature increases slowly all the way to the point where steam fills the cockpit (at about 190 per the gauge).

We have removed the heat exchanger and it is pristinely clean. There is plenty of water coming out of the raw water exhaust. There is no water in the oil. The transmission is getting very warm. The cooling system is set up such that engine coolant is running through the transmission/oil cooler and the exhaust.
Note: there is NO thermostat - apparently it was removed. We removed the water heater but left those lines connected to the old boiler/heat exchanger.

We did find that the engine coolant fitting at the transmission/engine cooler was out of shape and reshaped that to round, hoping that would solve the problem. Then ran the engine, in gear, at the dock, at 800 rpm for 50 minutes and the temperature only went up to 140.

Then yesterday we went for an engine check, motored at 1000 rpm for about an hour, and the temperature slowly and steadily rose to boiling with steam.

So, removed the coolant reservoir, found a missing thermostat, and here we are. We have two opinions from marine mechanics about whether to replace the thermostat. Could this be it or something else?

Read on another thread the engine coolant water pump gaskets are of differing size - is it possible to look to see if that's the problem?

Local water temperature: 79 degrees year-round for what that's worth
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Old 28-04-2013, 17:14   #2
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Re: Perkins 4108 Overheating/Steaming

I am sorry, I did not understand. You said there was no thermostat. Then you talked about an old boiler/heat exchanger. Then when you were telling about the coolant reservoir you found a missing thermostat.
My hot water tank has an internal coil that heats the potable water from the cirulating engine coolant. My coolant reservoir has no thermostat.
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Old 28-04-2013, 17:35   #3
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Re: Perkins 4108 Overheating/Steaming

I was told there was a thermostat located under the expansion tank. When I pulled the tank off, there was no thermostat. As far as the boiler goes, that was for potable water, and the water tank itself was rusted, so I replaced it with one that doesn't have the capability of using engine coolant - electric only. The original hoses and the boiler heat exchanger are intact.
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Old 28-04-2013, 17:55   #4
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Re: Perkins 4108 Overheating/Steaming

i had the same problem 2 years ago on my 4-108.

first, confirm that your raw water system is working. this is pretty much just looking over the stern to see if it's pumping water. you should be aware from past experience just how much water it should be pumping. if that looks good, check the place where raw and fresh water come together - the heat exchanger.

i have the old style 4-108 with a completely seperate heat exchanger, about the size of a 2 liter bottle of soda, with four hoses connected to it, which made it easy for me to check it. just take it off, remove the end cap, and look down the tubes. they should all be clear. if not, they can be carefully rodded out with a coat hanger size wire, then water flushed and reinstalled.

if good so far, look at the fresh water side. it's pretty simple. i had a thermostat, which i tested on the stove, but replaced anyway. made no difference. i eventually removed the thermostat altogether and have never reinstalled it. finally i came to the last piece of cooling system gear, and when i checked it, it all became clear what had happened.

the fresh water pump is belt driven off the engine - on mine the same belt also drives the alternator. i loosened the belt and spun the pump - it spun freely; it shouldn't. there's water on the other side of that pulley, and it should provide enough resistance to slow the pulley real quick. but it didn't. it spun like a top.the implication was clear. the pulley and and pump blades were not connected. replaced the fresh water pump and end of problem. examining the old pump, it was plain that the blade assembly was no longer connected to the shaft, so although the pulley turned at engine speed the blades turned not at all.

best of all, it only took me three days to find the problem......
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Old 28-04-2013, 17:56   #5
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Re: Perkins 4108 Overheating/Steaming

My 4-108 did exactly the same thing for years. The local mechanics in Tortola were unable to fix it. So were the expat mechanics in the BVI.

Out of extreme frustration, I flew in a friend from the States who is a master mechanic. He found three problems in a half hour, and had them fixed in about two hours.

Here are things to check:

1. Be sure the radiator cap is new/clean/making good contact so that pressure can build in the cooling system. This pressure is needed to raise the boiling point of the coolant.

2. Very important: when you replace the water pump, there is a thin flat steel plate which fits between the pump housing and the block. This plate has a gasket on each side These gaskets are not identical! If you don't use the right gasket, you will plug up an important port for coolant to circulate. This was the major problem with mine, and none of the local/expat mechanics had found it.

3. Just because a heat exchanger looks clean, and passes the "blow" test, doesn't mean it's OK. Mine had been cleaned several times, including the boil-in-acid treatment. But, it still wasn't up to the job. A new heat exchanger helped a lot. For awhile.

Important:
the heat exchanger on the 4-108 is way undersized. It's just barely able to keep up, even when brand new. I finally fit a larger Perkins heat exchanger -- I believe it's for a 4-236 -- and now, more than 14 years later, have never since had an overheating problem.

Here's a pic of the larger heat exchanger.

Click image for larger version

Name:	HeatExchgr.jpg
Views:	535
Size:	184.3 KB
ID:	60079

Hope this helps a bit.

Good luck,

Bill
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Old 28-04-2013, 18:31   #6
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Re: Perkins 4108 Overheating/Steaming

If my 4.108 has a little air in the fuel injection system it runs hot.
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Old 28-04-2013, 21:43   #7
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Re: Perkins 4108 Overheating/Steaming

Quote:
Originally Posted by btrayfors View Post
My 4-108 did exactly the same thing for years. The local mechanics in Tortola were unable to fix it. So were the expat mechanics in the BVI.

Out of extreme frustration, I flew in a friend from the States who is a master mechanic. He found three problems in a half hour, and had them fixed in about two hours.

Here are things to check:

1. Be sure the radiator cap is new/clean/making good contact so that pressure can build in the cooling system. This pressure is needed to raise the boiling point of the coolant.

2. Very important: when you replace the water pump, there is a thin flat steel plate which fits between the pump housing and the block. This plate has a gasket on each side These gaskets are not identical! If you don't use the right gasket, you will plug up an important port for coolant to circulate. This was the major problem with mine, and none of the local/expat mechanics had found it.

3. Just because a heat exchanger looks clean, and passes the "blow" test, doesn't mean it's OK. Mine had been cleaned several times, including the boil-in-acid treatment. But, it still wasn't up to the job. A new heat exchanger helped a lot. For awhile.

Important:
the heat exchanger on the 4-108 is way undersized. It's just barely able to keep up, even when brand new. I finally fit a larger Perkins heat exchanger -- I believe it's for a 4-236 -- and now, more than 14 years later, have never since had an overheating problem.

Here's a pic of the larger heat exchanger.

Attachment 60079

Hope this helps a bit.

Good luck,

Bill
Thanks, Bill, saw your post on an earlier thread. I looked at the engine coolant pump and only saw one gasket. Can both gaskets be inspected without removing the pump?
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Old 28-04-2013, 21:53   #8
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Re: Perkins 4108 Overheating/Steaming

By the way, the engine coolant is running through the dual engine oil and the transmission oil cooler. A local mechanic recommended plumbing this cooler with raw water. I'm wondering if the original heat exchanger is big enough to handle this load.
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Old 28-04-2013, 22:15   #9
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Re: Perkins 4108 Overheating/Steaming

don't agree with that. my coolant has been running that way for the past ten years i've owned the boat with no problems. probably the same for all 4-108 marine engines. you could wind up creating a whole new set of problems - like an overheating transmission. and there's no temperature guage on the tranny to warn you of impending failure....

i'd be wary of a mechanic who comes up with oddball solutions simply because he isn't able to find the problem.
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Old 28-04-2013, 23:02   #10
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Re: Perkins 4108 Overheating/Steaming

Edited for (hopefully) clarity:

Bought a 1978 Cal 39 about two years ago, and the (Perkins 4108) engine coolant pump was frozen. The local mechanic changed the pump and it worked okay for docking and short motors. When we began using the motor for over a half hour, we noticed problems.

The temperature increases slowly all the way to the point where steam fills the cockpit (at about 190 degrees per the gauge). The transmission also gets quite hot.

This is what weve done:
1. We have removed the heat exchanger for inspection and it is pristinely clean. There is plenty of water coming out of the raw water exhaust. There is no water in the oil.

2. We also removed the rusted-out potable water heater recently but left those lines connected to a little heat exchanger that used to slide into the potable water heater. Should we plug or remove these lines?

3. We ran the engine, in gear, at the dock, at 800 rpm for 50 minutes and the temperature only went up to 140. No leaks/no steam.

4. Then yesterday we went for an engine check, motored at 1000 rpm for about an hour, and the temperature slowly and steadily rose to boiling with steam.

5. So, we removed the coolant reservoir. I was told there was supposed to be a thermostat located under the expansion tank, but when I pulled the tank off, there was no thermostat.
We have received divergent opinions from local marine mechanics about whether or not to replace the thermostat.

6. We read on another thread that the engine coolant water pump gaskets are of differing sizes - is it possible to verify proper gaskets without removing the pump to see if that's the problem?

7. The engine coolant is running through the dual engine oil and the transmission oil cooler. A local mechanic recommended plumbing this cooler with raw water. I'm wondering if the heat exchanger is big enough to handle this load, especially as weve read others with overheating 4108s have solved their problem by replacing the original with a larger one.

8. Weve also read threads about how air in the cooling system can cause overheating, but cannot find any bleed screw. Is it worth trying and if so, what would be the procedure.

FYI: Local water temperature: 79 degrees year-round for what that's worth
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Old 29-04-2013, 07:59   #11
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Re: Perkins 4108 Overheating/Steaming

i would take the hot water heater out of the circuit completely by just removing the hoses from the heater and joining them together. i've done that to mine.

when i had my cooling problems the local perkins guy said i didn't really need the thermostat in florida/bahamas. haven't had it for years. when you finally get your engine running just make sure it comes up to operating temperature; if it runs too cool, you'll need to put the thermostat back in.

i guess at this point i would look for blockages somewhere. maybe by removing one piece at a time and pushing water through with a garden hose.

i think i would check that fresh water pump again. that was the last thing i checked and turned out to be the problem.
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Old 29-04-2013, 08:21   #12
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Re: Perkins 4108 Overheating/Steaming

I think you already have your answers....

1. Replace/pressure test your cap... check your cap mount surfaces... should not be blowing steam enough to fill the cockpit at 190....

2.Pull the pump.... Make sure one of the gaskets isn't blocking a passage... check pump shaft to vanes...
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Old 29-04-2013, 10:20   #13
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Quote:
Originally Posted by onestepcsy37 View Post
don't agree with that. my coolant has been running that way for the past ten years i've owned the boat with no problems. probably the same for all 4-108 marine engines. you could wind up creating a whole new set of problems - like an overheating transmission. and there's no temperature guage on the tranny to warn you of impending failure....

i'd be wary of a mechanic who comes up with oddball solutions simply because he isn't able to find the problem.
I had the same problem with my 4-107. Popped the cap on the heat exchanger and it was about 90% scale. I replaced all the raw water hoses, and most were very plaqued up with scale. The elbow between the oil cooler and heat exchanger was almost entirely blocked.

I back flushed and acid "boiled" all my heat exchangers in place. I flow tested each prior to the process because I'm just nerdy that way. With the back flush pump it took 25 seconds to flow a quart of water through the oil cooler before treatment, and 4 seconds post. That was the max my little pump could do on any of them.

That solved my issues. I think I'm over propped, so I can't turn full RPM without black smoke and getting hot, but I can make full cruising speed no problem now. The back flush boiling was easy to do, I highly recommend it.

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Old 29-04-2013, 12:47   #14
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Re: Perkins 4108 Overheating/Steaming

If you search this forum for the last few years, you will see that the "overheating 4.108" is one of the most popular thread titles. Lots of causes, most of them fairly easily fixable/explainable. Lot of information here, as
Ever-Popular Overheating Perkins 4108
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Old 29-04-2013, 19:25   #15
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Re: Perkins 4108 Overheating/Steaming

One other thing you might check is the hint mentioned in one of the posts above, the one about disconnecting your water heater from the circuit...for some reasons some installations like this with Perkins cause them to overheat. I don't remember the reason, but I think you can find it on this forum. The basic point is that the hose to the heater screws up the circulation and you get an overheat.
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