Perkins 4-108 losing coolant

[dneve]

The coolant level keeps going down but I have no visible leaks, installed new tube stack and rubber ends, no coolant in the oil, no overflow, and no coolant in the bilge, etc.
My mechanic thinks the Bowman heat exchanger/exhaust manifold may be cracked allowing coolant to go into the exhaust or into the seawater part of the heat exchanger. The other alternative is a bad head gasket or a cracked head.
The engine runs fine and no steam from exhaust. After about one hour of running, the coolant level drops about 6-8 ounces.
I am thinking I will remove the heat exchanger/ exhaust manifold and check it out . If no problem found, then I will remove the cylinder head.

Any suggestions from you Perkins guys??
Thanks

[kmacdonald]

Does it have a gear oil cooler? I would think it would overheat if it had a cracked head or block.

[dneve]

No transmission cooler and the engine is not over heating.

[kmacdonald]

If the exhaust manifold was made for fresh OR raw water cooling and it's fresh water cooled, there is a blocker plate between the exhaust manifold and riser that could be leaking. That would be great because it's cheap and easy to fix, just a new blocker plate and two gaskets.

[kmacdonald]

Check the fresh water pump also for leaks around the seals and the weep hole.

[SSgtPitt]

Removing the heat exchanger is a B#tch. At least it was on my boat. It sucked so bad I made a video of it and stuck it on youtube somewhere.
May I suggest you pressurize your coolant system with an air compressor, very low pressure, and check for leaks that way first. Do it when the engine’s cold and remove the t-stat.

[Mo Surprises]

My 4.236 was loosing coolant most of last winter while on a cruise and then mysterious stopped losing coolant. I can't explain why except that perhaps there was air in the system or a slight leak in my trans exchanger got plugged up. My water heater is above the level of my engine which could have the cause of the air. I'm about to do a coolant exchange and I'll be curious to see if the problem returns.

[zeehag]

check your pressurized cap. mine failed. first i saw missing coolant. ok. looked everywhere and kept filling it.
flushed the system and put in glowing neon green coolant for a test. found that in bottom of my bilges floating on my bilgewater. oopsy.
changed cap and ta daa no more loss.
try it . not pricey and doesnot entail removal of engine parts to find. one 10buck purchase and fixed.
now, it does not hurt anyone to maintain the cooling systems of engines,. but if it is the cap and you take down all other parts ignoring cap, you will only meet frustration

[thebootlegger]

Following ...thank you.

[FionaJC]

Originally Posted by dneve

.

Any suggestions from you Perkins guys??
Thanks

I fitted a Perkins 4107 with a bowman cooler last year and had the same problem. The pressure cap is a two way valve. It lets coolant out and sucks it back in if you have a header tank as the engine cools. I did not have a tank at first and lost coolant.

I changed the cap to a 13lb one, same problem. I cleaned the tube stack, cleaned the stack ends, rubber ends and tightenmed the jubilee clips round the rubber hose ends.

I still lost coolant.

I then added a header tank, no more problem. As the engine gets hot 105C (I think) the coolant goes out, as it cools down the coolant is sucked back in.

I am going on board Friday so I can post pix if you would like.

(By the way I am not a Perkins guy, I'm a Perkins Gal)

[sailon46]

One other thing that may reveal itself with cooling system pressurization is a leaking freeze plug. That was my problem and fixed it down in Curacao a couple of years ago.
Ernie on the Mary Jane

[Valmika]

I am seconding the heat exchanger. I had the same problem and was driving me nuts. Your coolant system is pressurized at about 15 Lbs. Your raw water is not pressurized. Even a small breach in the tubes between the two systems will result in the pressurized side(coolant) going into the Raw water side (saltwater) and out the exhaust. No signs of leakage in the boat

[Argyle38]

+1 on the vent tube/header tank suggestion. You would probably have evidence of a leak if it were coming out of the vent tube, but a small overflow tank is a good idea. Doesn't have to be special, you can get them at auto parts stores.

If you manifold is cracked, you would probably have coolant leaking down in to the cylinders and then in to the oil. This would obviously cause bigger problems and would show up in the oil at the very least.

-Edit: Valimka's idea about the heat exchanger is a definite possibility. Good call! Didn't think of that, was only thinking about the whole manifold casting.

Do you have the fresh water system plumbed in to a water heater? That can trap air and take a while for the air to percolate to the manifold tank. In general, this engine takes a while for all of the air to find it's way out of the system, so if you have just emptied the fresh water/coolant and are re-filling, just be patient, keep an eye on it and keep filling.

Finally, you said there isn't evidence of leaks, but have you looked on the side, under where the manifold bolts on to the head. If the mounting studs have ever broken off (somewhat common, they are undersized for holding a bowman manifold + water, imo) and the broken studs were drilled, it is easy to drill too far and in to the water jacket in the head. This will lead to leaks. You will see cooked antifreeze under and in the vicinity of the manifold mounting locations. The engine will also smell like cooking antifreeze when it's up to temperature. Don't ask me how I know.

[hellosailor]

There are other tests you can run before tearing things apart. There's a dye you can add to the cooling system which will turn color if exhaust gasses are getting into it, indicating a head gasket leak. Or you can pressurize the cylinders with an air pump, which can often tell if there's a head gasket leak.
Tearing things down can be simple, satisfying, and positive results, but if you can outsmart an engine, you don't need to get physical with it.

[Lodbrog1]

I had the same problem on my 4108 and was easily found by pressurizing the system to 7 lbs bc I have an 8 lb cap, and had inadequately torqued pipe clamps.