Ever-Popular Overheating Perkins 4108

[Trekka]

Another vote for getting an infra red thermometer.

In my case I damaged my Sherwood G65 pump when it ran for 10 mins with no water going through it. I had the boat hauled for a quick bottom clean and after starting the engine to motor back to the slip, for the first time did not check to make sure water was coming out the exhaust. The seacock was open but I guess there was an air lock. The pump began leaking a month later and I had a helluva time getting it off to rebuild. Finally got it off this weekend.

While doing that I also took off the heat exchanger - which I found to be over half clogged. Seeing that, I took off a couple of pipes that were part of the raw system and have descaled them too. But then I took off the coolant resevoir and found the inside covered in thick slime, as were all the hoses coming and going, and as far as I could see into the block and manifold cooler. (I would personally flog whoever designed this model of the engine where the resevoir has to come off to get at the thermostat!)

I'm going to have to find a way to clean all that FW cooling tubing. Suggestions? I can use dilute muriatic acid on the portions I removed, but don't want to run that through the block.

[Trekka]

While I'm taking this beast apart.. anyone ever dealt with the oil cooler? I'm wondering what the construction is inside and whether I should take it of for cleaning the coolant portion.

[Maddog]

My 4-107 was also over heating. When I rebuilt the cooling system and started it up, the temp gauge immeadatly red lined at 230+. A mechanic showed me a trick that is in the 4-107/4-108 shop manual. There are 2 screws in the top of the manifold, (front and back of the engine), that vent the cooling system. You may have square headed screws or temp sensors in them. I topped off the cooling system through these holes and cleared the air lock at the top of the manifold. I have run at a steady 180 ever since.

Try the simple things first.

[jlogan]

I ordered a new gauge and sending unit from Transatlantic Diesel (thanks Sherri). So to speed up the process, I thought I would use Gordon May's instructions for testing a gauge and sender to see if that was really the problem. On a Gulfstar 37, at least mine, the gauges are to the right of the wheel, mounted low on the cockpit. Whoever had last reinstalled the gauge panel had decided to use something like 5200 to reinstall....much fun to remove without destroying guage holders....anyway, what I found was that there was a problem with the sender wire attachment to the block....I had put a new end on it a year or so ago, but evidently the vibration had broken almost all of the old wire with the exception of 1 strand...this boat from 1979 had plain copper wire, not tinned, and not multi-strand very flexible like to days standards. Anyway, after puttering around with this for a while, installing new ends and refitting everything...took off down the lake to see what would happen....gauge went immediately to about 180...and stayed there...no overheating...problem solved, or so I thought...after about 2 hours of run time, the guage jumped up to about 220, for no obvious reason....so I am assuming gauge broken, which is what some of Gordon's tests showed, although it seemed to work for a while. I should get new gauge and sender on Thursday or so, and will install, and report back...

The moral here is to actually flex and check terminal ends on older wires to engines...and based on what I found, I think running a new sender wire of modern tinned multi-strand wire of appropriate size is what I am going to do when I get the new gauge set..I suspect that somewhere in the wiring harness between engine block and cockpit, there is a broken or almost broken spot in the sender wire that is acting as some sort of variable resistance, thus making the gauge unreliable...thus new wire when installing...

here's hoping that I am lucky enough this is the real problem and it will be fixed by this repair...stay tuned...

[jlogan]

I replaced the temperature sender and gauge today, had to remove the expansion tank to change the sensor, so checked the thermostat as well...would have put in a new one, but didn't have one available. I tried it in hot water and it opened, so I assume it works..

Anyway, new gauge and new sensor and new wire...and still showing problem...220...but stays there.

Is is possible that the gauge and sensor are mismatched and both are working correctly, but the sensor is not calibrated with the guage and that is causing the problem?? I bought them both from Transatlantic Diesel, usually they are good at sending you what works...

Anybody got any ideas? I really don't think it is overheating, but the gauge is saying it is...next purchase is infrared temp gun as several have suggested..

My country boy way of telling it is not too hot is that when it is showing 220, I can touch the temperature sensor for several seconds...There is no way the temp sensor is 220 degrees farenheit, and it would seem that it would have to be for the sensor part to read that high.

Any ideas??

[never monday]

Originally Posted by jlogan

Anybody got any ideas? I really don't think it is overheating, but the gauge is saying it is...next purchase is infrared temp gun as several have suggested..

trust but verify. You could stick a meat thermometer in the heat exchanger at the radiator cap.

[jlogan]

Originally Posted by never monday

trust but verify. You could stick a meat thermometer in the heat exchanger at the radiator cap.

Pat - you've been dispensing advice that makes sense for lots of years...so why can't I think of this stuff when I am up to my elbows in engine parts, coolant tanks, and such??

Guess I better stick to my day job..

Thanks for the tip, I'll try this...although, I would guess if it is not boiling out the radiator cap, it obviously isn't 220 degrees....+

[never monday]

Originally Posted by jlogan

Thanks for the tip, I'll try this...although, I would guess if it is not boiling out the radiator cap, it obviously isn't 220 degrees....+

depends on the coolant mix. My Jeep runs 210 all day long and doesn't boil over.

[jlogan]

I bought an infrared external surface temperature device. When the engine is running under load, the temperture on the gauge/sensor combo I just installed indicates 215-220 degrees F.

I used the IR device to check this guage indication. I calibrated against two other thermometors and against a pot of boiling water +- 1 to 2 degrees difference, so it seems to be accurate.

With 220 on the gauge...the temperature of the header tank indicates 168 degrees F, block surface next to the temp sensor, 169-170, front top surface of the exhaust manifold, 169, rear top surface of exhaust manifold, 174, and the exhaust elbow just past where the water is injected, 98 (!) degrees, almost cool to touch. Valve cover temp is 140 degrees.

So obviously, after new impeller, flushing of all intake and other hoses, new Speed-Seal raw water pump cover, remove and acid bath and cleaning of heat exchanger, I don't have a real overheating problem, just a mismatch between gauge and sensor.

I bought the gauge and sensor from TA diesel, so I am communicating with them to see if they have a fix. As much trouble as it is to take off the tank to get to the sensor, I may just fix it with a dab of green paint on the gauge to indicate "normal"

None of the effort was wasted, as I think almost any older diesel would benefit from having the raw water side cleaned and "rebuilt" ever so often. Now though, I can work on some other important project, such as that third coat of Cetol that I never got on..

[funsailthekeys]

I have replaced anything that could be replaced in the cooling system and acid dipped the exhaust elbow it still pegged out at 240. I bought a laser thermometer and while the gauge said 240 the laser said 163. I have run the heck out of it and the hottest the laser says is around 168. So much for 23 year old gauges.

[Cheechako]

Returned a boat from Tini to Fla with overheating problems and attempted solutions all the way. Finally someone figured out that it was the temp sender, no overheating after all! Did you check your actual temperature with a good digital or other thermometer? Reducing prop pitch a possible solution too. 190 sounds good though. better than 170 for engine life...

[btrayfors]

I believe there's a conspiracy afoot on the part of (mainly Chinese) temperature sensor manufacturers to drive us crazy!

The sad truth is that NEW TEMPERATURE SENSORS -- RIGHT OUT OF THE BOX -- CAN YIELD WILDLY DIFFERENT RESULTS.

One poor soul had tried three new temp sensors for his batteries (running to a smart regulator). Two of these read much higher temps than actual, causing the regulator to shut down the flow of charging to the batteries, while the third sensor read much lower temps than actual, causing the regulator to think the ambient temperature was very low and to increase the rate of charge. Both, of course, are highly undesirable....and even dangerous....scenarios.

Many temperature sensors use thermistors, which change resistance according to temperature. But, it would seem, their consistency and reliability is called into question, especially in terms of products currently hitting the market.

Not sure what the fix is. I'm trying to interest some techie friends in a small study and article which would examine the present situation and provide some help/guidance for boat owners.

Bill

[SkiprJohn]

Congratulations! Another overheating Perkins 4-107/4-108 that isn't overheating. I'll bet you feel good about the fact that you discovered the problem, its not serious and now know how to cure it.
Kind regards,
JohnL

[alibaba.e]

Originally Posted by jlogan

I've been working on what seems to be an overheating problem in my 1979 4108 in a 37 Gulfstar for about a year now. So far...removed and acid washed heat exchanger, new coolant, new impeller. Engine seems to want to run at 190 F instead of 180 F, no matter what the RPM (within reason). The water coming out of the exhaust is barely warm when the boat is up to the 190 operating temperature. I don't think I have any head gasket or transmission oil cooler problems as there are no symptoms (disappearing coolant, oil in coolant, overheating beyond 190/200f, etc.)...by the way, the boat seems to have had this problem since I bought it...tested in January, no problem, water getting warmer, problem...

2 Questions on which I would appreciate opinons/answers.

1. How likely is it that this is just a temp guage/sender issue given that the water coming out of the exhaust is barely warm (you can hold your hand in it all day)

2. I probably will order a new raw water pump, but how does one determine if an old raw water pump is worn out? This one appears very shiney inside, the face plate is scored and worn, but the cam appears ok and has no worn ends or sharp edges like you see in a worn pump. I changed impellers, even though the old one appeared fine. Water flow looks the same...about like a wide open faucet at all times, and the usual big slug of water every other second or so, when running at 1500-1700 rpm. More rpm, more water flow, as usual...could just the worn end plate cause this sort of problem?

Not actually wanting to change pump, as we are looking at $500 or so, but can't see that rebuilding current pump is a good idea if it is worn enough to cause this problem

any ideas? This is running me nuts, usually I am a pretty fair mechanic, but I hate just changing parts without any idea of why I am changing them...

Open water cap slowly or before you start and hold a oven type thermometer in water tank and read temp when engine warm. 190 degees is a normal operating temp. If the oven thermometer reads the same as ship gauge then you will need to change the thermostat if you want a lower temp. If temps are different well then it is gauge or sending unit.
Good luck

[Cheechako]

190 should be a good operating temp if it stays down when loaded up hard. Running too cool will harm the engine more than running at that temp or a little higher. Tried running the boat tied (well tied!) to the dock/strong cleats for 15 minutes or so? If you can do this at near cruising rpm and it doesnt heat up I would say you are good to go. I have found a Probe Thermometer ($35 digital, Graingers) to be a useful tool over the years. Are you sure you are getting adequate water out the exhaust? a restricted Exh elbow might cause low flow