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Old 04-01-2010, 21:59   #1
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Perkins 4.108 Overheating Problems

First post, so be gentle!

Yet another overheating 4.108. I've not had a problem with my engine at all. Normal operating temp under all conditions. Went from zero problems to overheating.

Here's what happened: After something like 45 minutes of normal running (1750 rpm), engine suddenly overheated. I was more than fortunate to got the boat back to the dock without too much trouble, but the engine would not run at anything more than an idle for more than 5-8 minutes before overheating again.

Here's what I did:
1. Checked alternator belt - Intact and tensioned. Checked coolant level- It was good. Checked raw-water flow - It was good. Checked the entire raw-water circuit for any obstruction, component failure or leakage. This included the through-hull, raw-water strainer, raw-water pump (including impeller), heat-exchanger and tubing stack. All is fine here. Normal flow, no obstructions, all parts in good order and serviceable.

2. Begin to check freshwater circuit. First thing I suspected was a stuck thermostat. Removed same and replaced with a new one. Checked both the old and new one to make sure they were working. All fine. Installed new thermostat and gasket and ran engine. Overheated immediately.

Perhaps a vapor lock? I drained all fresh-water coolant from the system, removed the pressure cap from the header tank/heat exchanger, and the water-temp sensor fittings from the front and back of the cylinder head. I added 50/50 coolant at the highest point (expansion tank above all hose runs) until coolant flowed out of the water-temp sensor locations. Refitted those and added coolant until it flowed out of the top of the header tank/heat exchanger.

Started engine, waited a few minutes until it was "warm" then backed off first the forward temp-sensor ensuring there was no air present, then the rear fitting. Engine overheated.

Perhaps a blown head-gasket or cracked head/block? No oil in coolant or coolant in oil. At least by visual inspection of the dipstick, beneath the oil filler cap or in the coolant itself. Engine is not smoking abnormally (no clouds of white smoke or sweet-smelling exhaust). I checked the coolant with the pressure cap off to see if there was any bubbling. None. At least none I could detect visually.

Perhaps the freshwater circulation pump? It's not leaking externally, not making any strange noises. BUT, and here's the rub, there seems to be no freshwater circulating. Despite the engine overheating, the freshwater hoses all remain cold to the touch (water temp around here at this time of year is 44). The header tank/heat exchanger is too hot to keep your hand on, but the hoses are cold. Lift muffler is cool. Injection elbow is cold.

Since the freshwater pump pulley and the pump vanes are press-fit onto the same shaft, if the pulley is turning, is not the vane turning as well? And if that's the case, shouldn't the pump be pumping?

So, my questions are these:
1. Can the freshwater pump fail so that it stops pumping coolant? I can only find reference to freshwater pump failures that include leaking fluid externally or oil internally. But nothing about them turning and not actually pumping.
2. Did I miss something or do something wrong when it came to bleeding the freshwater cooling system? There doesn't appear to be any physical blockages in the system. I don't suspect any physical blockages as there is no indication of a gradual build-up of scale/sludge as the system never had a tendency to overheat. But no coolant flow would suggest an obstruction...
3. Can a blown head gasket or cracked cylinder/block stop coolant from circulating?

I've been reading around this problem for a couple of days now without making any more progress or knowing what to try next. I'm at my wits end and would appreciate any thoughts or advice!

TIA
Bert
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Old 04-01-2010, 22:29   #2
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Bert-
It sounds as if you've taken the same diagnostic approach as I would have. If the water pump vane is still firmly pressed on the pump shaft, then I think you can safely assume that it's doing it's job.

This one's a stinker. I don't have any good suggestions although a friend of mine did have a similar problem and it turned out water jackets were just plugged up with junk. Even though he was an excellent mechanic, he called in another mechanic who added some very strong cooling system cleanser to the system. Once it was cleaned out the problem disappeared. I've no idea if that's your problem. Just an anecdote at this point. Good luck.

Fair winds and calm seas.
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Old 04-01-2010, 22:41   #3
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Sears has an infrared temp sensor....I saw them on sale for about $20 US.

It may be helpful to you to find hot spots.
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Old 04-01-2010, 23:24   #4
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Bert-
It sounds as if you've taken the same diagnostic approach as I would have. If the water pump vane is still firmly pressed on the pump shaft, then I think you can safely assume that it's doing it's job.

This one's a stinker. I don't have any good suggestions although a friend of mine did have a similar problem and it turned out water jackets were just plugged up with junk. Even though he was an excellent mechanic, he called in another mechanic who added some very strong cooling system cleanser to the system. Once it was cleaned out the problem disappeared. I've no idea if that's your problem. Just an anecdote at this point. Good luck.

Fair winds and calm seas.
I'll give this a try next. Perhaps remove thermostat housing and thermostat, loosen alternator belt and turn the circulation pump pulley by hand. That "should" pump coolant, albeit slowly. Or perhaps I'll kick the engine over to see if I get coolant flow. Not sure about that though as I checked for coolant flow with the pressure cap off and the engine running. Nothing! But it can't hurt to flush the system. When I drained it, the coolant looked OK. Not discolored and not full of sludge and debris. However.....

Thanks for the response!
Bert
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Old 04-01-2010, 23:25   #5
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Originally Posted by Chief Engineer View Post
Sears has an infrared temp sensor....I saw them on sale for about $20 US.

It may be helpful to you to find hot spots.
Good idea. I'll grab one and see what I can see. Hotspots might indicate a leaking head gasket? Blocked passage?

Thanks
Bert
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Old 04-01-2010, 23:57   #6
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Leave the thermostat out, and try again. That infrared sensor would also tell you whether the problem is simply the temperature sensor.
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Old 05-01-2010, 08:54   #7
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Sorry to hear that you are having problems, but it very simple to track down the culprit. You have to go through a process of elimination. Many things you have already done. I would concentrate on the heat exchangers and eliminate them from the list next.
1. Check your sea strainer and through hull valve.
2. Check your raw water impeller. (If it is damaged, replace it, the broken pieces will be lodged in your transmission cooler and your engine cooler so they will have to be removed and cleaned. It is possible that a prior owner replace an impeller in the past but was to lazy to pull the coolers. Use muriatic acid for scale and build up and remove rubber pieces by hand. Do not poke things into the coolers) Lubricate new impeller with dish soap before replacing.
3. If have removed the thermostat make sure that it has not been put in backwards.
4. The engine cooler will have a zinc anode in it replace it after cleaning. You can leave it out to bleed the system then replace it. Make sure you have plenty of flow over the side.
5. It is not normally a good idea to rev the engine as high as it will go, 2000 rpm is good after that you get minimal speed increase and burn allot more fuel and stress the engine.
Once you have completed this you should be good to go. If not flush the block with muriatic acid or other engine flush and chase with water away. Do not leave acid in the block to long.

I owned a 16 ton 39'Sail Boat with a 78/79 M4108. I experienced the problem that whenever it was above 2200rpm the heat alarm would go on. For years we could not figure it out. Last year we happened to make adjustment to change the fan belt and alternator and since then the problem is gone. Interestingly the perkins recommended fanbelt was too tight. We got a slightly bigger one from NAPA.

go read some posts here from last year. Sounds like you two have the same boat!
Ever-Popular Overheating Perkins 4108

Good luck.
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Old 05-01-2010, 09:01   #8
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Bert - I had a similar problem on mine, but it was vapor lock at the sensor. You've cured that. All I can offer is to fix the cheap things first. Check the gauge and sensor, get the IR thermometer and play around, disconnect all the hoses and re check them.

Good luck, that's all I got.

Please tell us what you find, we all need to learn.
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Old 05-01-2010, 09:20   #9
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As the zincs erode away, bits will get stuck in the heat exchanger.
With no flow in the fresh water side, it's got to be one of two things.
1- the pumps not pumping, vanes rotted off or air in pump.
2-heat exchanger plugged.
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Old 05-01-2010, 11:10   #10
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with the 4108, there is a fine line between hot and damn hot.. If you can back off on the rpms to an idle and the temp stays or drops, its the impeller housing.. I've worn out a couple over the years.. I had the problem of overheating.. changed out the impeller, changed the cap, and all the time, large amounts of water were comming out the back.. but the impeller housing was worn out along with the shaft.. Put a new one on and at a high price and all was fine.. remember the pump is fitted to the front of the cam so only pull the pump.. not the alignment plate..
If the shaft is ok, you can get by - by just replacing the inside of the pump. you'll see the removable plate but if you have any play in the shaft, the whole unit needs changing..
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Old 05-01-2010, 11:52   #11
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A classic cause of overheating on the 4.108 is the exhaust elbow becomes plugged with crud, easy to remove and inspect, also ditto the heat exchanger bundle, easy to remove and inspect to see if plugged, if it turns out it needs cleaning Perkins says no muriatic acid, the engine manual specs what should be used to clean with.
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Old 05-01-2010, 12:52   #12
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Bert,
Do you have a water heater warmed by the engine? I had a similar problem with a Yanmar 2GMF. I turned out that the water heater was full of air preventing the water pump from pumping even though everything else was full of coolant. I disconnected the water heater and flushed the from the bottom up with a garden hose. Reconnected and no more overheating.

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Old 06-01-2010, 09:44   #13
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Originally Posted by cdennyb View Post
Sorry to hear that you are having problems, but it very simple to track down the culprit. You have to go through a process of elimination. Many things you have already done. I would concentrate on the heat exchangers and eliminate them from the list next.
1. Check your sea strainer and through hull valve.

Done. All is good.

2. Check your raw water impeller. (If it is damaged, replace it, the broken pieces will be lodged in your transmission cooler and your engine cooler so they will have to be removed and cleaned. It is possible that a prior owner replace an impeller in the past but was to lazy to pull the coolers. Use muriatic acid for scale and build up and remove rubber pieces by hand. Do not poke things into the coolers) Lubricate new impeller with dish soap before replacing.

Raw water impeller is good. I had the header tank and heat exchanger tube stack removed and cleaned. It's good, too. No transmission or oil cooler, therefor rubber bits lurking about.

3. If have removed the thermostat make sure that it has not been put in backwards.

Thermostat properly installed.

4. The engine cooler will have a zinc anode in it replace it after cleaning. You can leave it out to bleed the system then replace it. Make sure you have plenty of flow over the side.
5. It is not normally a good idea to rev the engine as high as it will go, 2000 rpm is good after that you get minimal speed increase and burn allot more fuel and stress the engine.
Once you have completed this you should be good to go. If not flush the block with muriatic acid or other engine flush and chase with water away. Do not leave acid in the block to long.

I owned a 16 ton 39'Sail Boat with a 78/79 M4108. I experienced the problem that whenever it was above 2200rpm the heat alarm would go on. For years we could not figure it out. Last year we happened to make adjustment to change the fan belt and alternator and since then the problem is gone. Interestingly the perkins recommended fanbelt was too tight. We got a slightly bigger one from NAPA.

go read some posts here from last year. Sounds like you two have the same boat!
Ever-Popular Overheating Perkins 4108

Good luck.
So far, no luck. Still working though. Will post progress...
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Old 06-01-2010, 09:50   #14
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with the 4108, there is a fine line between hot and damn hot.. If you can back off on the rpms to an idle and the temp stays or drops, its the impeller housing.. I've worn out a couple over the years.. I had the problem of overheating.. changed out the impeller, changed the cap, and all the time, large amounts of water were comming out the back.. but the impeller housing was worn out along with the shaft.. Put a new one on and at a high price and all was fine.. remember the pump is fitted to the front of the cam so only pull the pump.. not the alignment plate..
If the shaft is ok, you can get by - by just replacing the inside of the pump. you'll see the removable plate but if you have any play in the shaft, the whole unit needs changing..
Engine will overheat in something like 8-10 minutes when it's kept at idle. The raw water pump is relatively new (about 270 hours). Raw water side seems fine. With the engine overheating, all fresh water coolant hoses are cold/cool to the touch. Heat exchanger and cylinder head are too hot to touch. My ten "digital" thermometers tell me this ain't right!

I"m going to concentrate on the fresh-water side...

Bert
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Old 06-01-2010, 09:53   #15
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A classic cause of overheating on the 4.108 is the exhaust elbow becomes plugged with crud, easy to remove and inspect, also ditto the heat exchanger bundle, easy to remove and inspect to see if plugged, if it turns out it needs cleaning Perkins says no muriatic acid, the engine manual specs what should be used to clean with.
I checked the elbow late last summer when I replaced a short length of exhaust hose. All fine - No corrosion and no blockages. Still thinking fresh water side...


Bert
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