Perkins 4.108 Over Heating

[MV-Romnya]

Not sure if this is the correct forum but will try - Thanks for all your help in the past and am sure there is someone out there with the same problem.

I last posted about my mate running my boat aground in the mud now I think I got mud and stuff all through my cooling system it is running extremely hot (125c) . The water pumps out of the exhaust ok but I noticed that the water pipe coming from the engine block to the exhaust manifold is very hot but the water pipe from the exhaust manifold to the heat exchanger is cold as ice.

Help please on how to flush the whole system - the thing has water pipes running all over the place - MVR

[Celestialsailor]

The exchange units on the 108 are notorious for not cool with the slightest amout of crap or scale in them. The only efficient way of dealing with them is to take them to a reputable radiator place and have them flushed and cleaned bright.

[MV-Romnya]

Thanks C - water does come out of the exhaust - any more thoughts - Joe from New Zeland has been a great help with emails - RMV

[Celestialsailor]

On both the 108 and the 236, I have seen minor scaling were there was lots of water flow but it still heated up higher than desirable until it was flushed with chemical at a radiator shop. Another thing that could have happened is that when your friend went aground, a blade on the prop bent and is taxing the diesel and cooling system. could also be something as simple as a slightly clogged thru-hull inlet or sea water strainer has weed in it. I have also seen pieces of bark accumulate and get stuck in elbows at the sea water straiiner.

[DeepFrz]

I would recommend you flush and clean your raw water system from the sea cock to, and including, the water injector at the exhaust mixing elbow. It might even be necessary to flush the water lock muffler, depending on the type of mud that has been ingested.

[phorvati]

Originally Posted by MV-Romnya

I noticed that the water pipe coming from the engine block to the exhaust manifold is very hot but the water pipe from the exhaust manifold to the heat exchanger is cold as ice.

That sounds like clogged exhaust manifold or fresh water side of heat exchanger.
You can spend money on the radiator shop or you can do this...

Cleaning Marine Diesel Heat Exchanger - YouTube

I always wondered how to measure fresh water flow. You can measure raw water flow with a bucket and a stopwatch, but you never really know what goes on on the fresh water side.
Putting flow meter at the output of the heat exchanger would be a way to get some valuable info on the state of fresh water circuit. Has anyone done that. Would need 1-1/4" barb fittings for flow meter. And flow meter with high temperature rating.

[MV-Romnya]

Thanks all - I have googeled & youtubed all perkins engines I can see anr read but mine is totally different - yesterday I leaned heaps about my 4.108 from Joe of NZ. The thing that has got me absolutely confused is that the engine coolant is a closed system and the coolant runs through the HX. When I started the engine I held one hand on the coolant pipe coming from the engine which goes to the exhaust manifold and the other hand on the coolant pipe going from the exhaust manifold to the HX and guess what the engine side was hot and the other was cold so is something stuck in the manifold - also I can only see one pipe from the engine block and another from the coolant header tank to the thermostat on the engine head - I am at a loss because the boat is in a remote location in southern Australia and the mechanics (only 2 of them) are not familiar with the perkins engine so I turn to all you nice people in this forum - thanks - Karl

[sailorchic34]

The raw water side will always be much cooler then the closed loop fresh water side. Whats important is the temperature difference between the raw inlet water and the raw water discharge before the discharge elbow. But probably only a 10-20 degree C difference or less to the raw water inlet temperature. For example if you have 20 degree C raw inlet water, you might get to 30-35 degree C on the discharge. Thats as it should be..

The closed loop side should be 80 degrees C +/- 5 ish degrees.

[DeepFrz]

Maybe you need a larger heat exchanger?

Truck Mounted Bundle Extractor -- Peinemann Equipment - YouTube

[onestepcsy37]

i learned more about my perkins 4-108 cooling system than i wanted to last summer in the bahamas.

if you indeed sucked mud into the cooling system it's good to know it's all on the raw water side. all the pieces of the raw water side are external to the engine and can be disassembled and inspected for clogging - including the heat exchanger. don't forget the oil cooler lines. but you say that the overboard discharge is ok which i interpret to mean it's pumping as good as it was before you had the overheating problem. so if you've done all that then the problem is on the fresh water side.

the fresh water side is mostly internal to the engine and will not have sucked in any mud. you can still do an inspection of it. there are two hoses external to the engine block that go into the heat exchanger. there is a thermostat under the header tank. if you live in a warm climate like i do you can just discard it if you like, or replace it for a few dollars. if you have a hot water heater in the system there will be two hoses going to that which you can inspect. it may be difficult to inspect the hot water heater itself but you can probably force water through it to make sure it's not clogged.

now we come to the last bit. the fresh water pump. it was my privilege to make perkins history in the abacos by having the only fresh water pump failure that my mechanic had seen in his thirty years of servicing perkins engines. it was the very LAST thing that i inspected, and i correctly predicted that it was the problem by simply spinning it. i loosened the drive belt (it's driven by an external pulley on the same belt that runs the alternator). then i spun the pulley by hand. it spun freely. it shouldn't spin freely because there is a vane on the inside and the vane sits in coolant and the coolant should slow it down. obviously, the pulley and the vane were no longer connected. it was at that point that i visited the local engine shop - marsh harbor marine. the guy who runs the place is a super dude and a factory trained perkins engine guy. knew the 4-108 inside and out. said he had never seen a fresh water pump vane seperate from the shaft. but he pulled it anyway (i had trouble getting out the four bolts as they hadn't been moved in thirty years) and sure enough the vane had come loose from the shaft. one week and $400 later i was back in business.

as for the heat exchanger, it's an easy pull. just make sure you put the four hoses back where they belong. it's held on by two straps. remove the hoses, remove the straps, and pull the heat exchanger away. there is a bolt on one end cap that lets you open it up for inspection. you'll find several dozen small tubes running the length of the exchanger. these are the raw water side and will be where the clog is if there is a clog. you insert a wire in each tube and make sure you hear it hit bottom on the other end. then you'll know the tube is clear. if it's not, try clearing it out with the rod but be careful you don't pierce the wall of the tube. flush the whole thing out with a hose and put it back together. change the zinc while you're at it. then put it back making sure you put the hoses in the correct place.

now you know everything i know. aint much, but when you're away from civilization and something breaks, you learn quickly....

[MV-Romnya]

Thank you all and onestepcsy37 and Joe from NZ (via emails) deserves a GOLD medal for all that info because I think I have the same problem - nevertheless I shall take all your advice and do as you suggested - one last thing .......I think this is how it works (advise from the local boat toy shop) the fresh water starts from the bottom of the engine block then goes up the engine block to the top where there is a thermostat then to the header fresh water tank then into the heat exchanger and then to the exhaust manifold and then out of the exhaust manifold to the bottom of the engine block. I am advised that the thermostat will open at 83 c to commence the cooling cycle - any thoughts ?? - MVR

[onestepcsy37]

the thermostat is located under the header tank. the header tank is held down by two long bolts - i think one is longer than the other (maybe) so if it is keep track of which one goes in which hole. there may also be a small pipe fitting on the side of the header tank which you can just back off and separate from the header. then lift up the header tank. you will find the thermostat there.

you can check the thermostat by putting it in a pot of water on the stove. you'll need a thermometer to check water temperature as it heats up. 83 centigrade sounds a bit high to me - but then we yanks think in farenheit. i think it opens at 140F to 160F. but if you live in a warm place you can just toss it in the parts box. the mechanic told me it was not needed in the bahamas so i never put it back in. hasn't hurt the engine one bit and it's one less thing to worry about.

i'm not what you would call a mechanic. but i decided to diagnose the problem myself with the help of the perkins engine manual. took days but when you're anchored in paradise who really counts days? also, i had stopped by the mechanics place and told him my problem and what i was doing to find the solution and he was extremely helpful. when i finally got to the spinning pulley on the fresh water pump he was actually puzzled. said he'd been trained in england on the 4-108 and had never heard of a fresh water pump pulley spinning freely, but acknowledged that it was likely the problem.

the good news is that when this is all over you will know a heck of a lot more about your engine and be a better cruiser for it....

[MV-Romnya]

Thanks onestepcsy37, with all this wonderful information I can now establish the exact problem. I am going to post a new thread in the engineering section of this forum with a couple of pictures to see if anyone can identify the type of HX I've go. Yours seem a bit different to mine - one more thing - what damage can heating do to an overheated engine and what are the tell tail signs of over heating damage - MVR

[forsailbyowner]

tell talesign would be losing coolant. Im aware of two types, the lowline engine with the cylindrical heat exchanger at the back of the engine and the bauman (sp?) that is located in the exhaust manifold. Are you losing coolant out the cap? Have you checked the temp guage or useda pyrometer to see if the engine is actualy that hot? Ive been through 3 guages/senders so far.

[MV-Romnya]