4-53 - exhaust in coolant

[kflod]

Hi,
I just bought a Hatteras 42 Long Range Cruiser (1980 mkII).
It has two Detroit 4-53N with only approx 1000 hours on them. I bought the boat in England and am taking her back to Norway. I had the engines serviced before departure, and the first 40 hours of nonstop cruising at 2000 RPM's went without any problems. They have used perhaps in these 40 hours 2 liters pr engine. However, there were a bad leak from the sea water pump (Jabsco 17050-0001), so I decided to stop in Rotterdam, Netherlands to have it repaired. After a more or less rebuild of the pump, I started heading home again.

After one hour of 1500-1800 RPM going out from Rotterdam, I put her at 2000 RPM. Going 15 mins everything ok, but then, in perhaps two or three minutes, the port engine temp increased to 210 F. I pulled the engine to idle and shut it down immediatly. I looked in the engine room, and the hose going up to the heat exchanger from the underside indicated a massive pressure, as it was like a balloon!

I realized it was about to burst and closed the engine room. When I looked it at again after 15 minutes (when the engine temp was normal - didnt start the engine, only the instruments) it had burst, spraying black/red coolant everywhere.

Obviously, exhaust had found its way to coolant, causing pressure and discoloring of the coolant. normally the cap on the heat exchanger would have opened, but the old hose was the weaker link.

The next day I started the engine for a few seconds (didn't have a new hose) to see if water came out the exhaust pipe. So it did, and a inspection of the impeller found no faults either. So appaerantly nothing wrong on the sea water side. And luckily the engine ran good these few seconds.

Now - I have a few questions;
1. any typical causes for this? Do you think it is a broken gasket somewhere?
2. should I worry that I have a cracked cylinder head, or something else?

Very thankful for any help!

Kristian

 

[Seabrooke]

Not knowing the nuts and bolts of a DD, but having lots of experience on other engines, I would expect you at least have blown a head gasket. The next most likely (& by far the least wanted) is a cracked head.

If the engine sounded okay for those few seconds when running cold, it sounds like the fault is opening up when the engine comes up to temperature.

My suggestion is.... Don't start the engine again as there is also a chance that the effected cylinder will have filled with coolant and you will have an hydraulic lock when you try to start it again and may cause more damage. It may have, by chance, stopped at top dead centre last time and not had any coolant leak in before you started it.

If anybody else has further suggestions and (most likely) more experience with DD's please add your thoughts. I'm perfectly happy to be proven wrong here.

Hope this helps a little and good luck.

 

[Avenger]

Are you sure it's not motor oil? Seems odd that exhaust would soot up the coolant. Also, why wouldn't the cap vent the pressure before it blew a hose off?

 

[DCMY #92]

kflod

I have owned 6V53s for many years that I have overhauled a couple of times. I'm not specifically familiar with the 4-53, but it can't be much different. When you say the hose going up into the heat exchanger burst, what hose is this. Is it the hose from the coolant circulating pump to the heat exchanger?

The 53 series has wet liners with O-ring seals to to the air box. This requires a low pressure radiator cap. I think the correct pressure cap is 7 psi. The exhaust pressure should not be more than a few inches water head (much less than one psi) so I can't see how exhaust could pressurize the coolant even if you had a leak between the two systems. I suspect he black was not soot from the exhaust , but just rubber debris from a rotten hose.

The only location I can think of where exhaust and coolant could mix if a leak were present is in the exhaust manifold or gasket joint between the exhaust manifold and tail piece. The tail piece is the bit bolted to the rear end of the exhaust manifold into which the exhaust riser pipe is screwed. I have had leaks at this joint, but the coolant pressure is much higher than the exhaust pressure so the coolant escapes into the exhaust. The engine will eventually overheat due to low coolant level.

I think that you had a very rotten hose. Plus, maybe your coolant cap is incorrect and maintains too high a pressure in the coolant. I suggest that you check the cap's pressure rating. If the label says 7 psi either replace it with a 7 psi cap or have it tested to see if it is defective. If you don't have access to a new cap or test equipment, then leave the existing cap loose so no pressure can develop and go on your way - carefully watching engine temperature.

Please let me know what happens.

 

[Seabrooke]

Are you sure it's not motor oil? Seems odd that exhaust would soot up the coolant. Also, why wouldn't the cap vent the pressure before it blew a hose off?

A good point Scrod.

Kristian, if you haven't already, check the engine oil for water/coolant contamination.

This will typically be in the form of thick brown texture or "milkiness" or possible "sludge" in the oil.

This could still be head gasket or head as the cause.

If the oil is "sludgey" but black, it's not water. That's just really poor maintenance and the oil is WELL overdue for a change.....

As you have blown a hose rather than had a cap venting, it's probably VERY old and fatigued. I'd be checking ALL other pressure hoses immediately. It's also be checking the cap.

 

[mr hatt]

As the others here have said. Detroit's don't like to get hot. Past 195 you can boil the coolant around the cylinder inserts which just have an o-ring seal. 4-53 is s simple engine so you should be able to sort any damage out fast. Good luck.

 

[rmatt]

Get the jacket water cooling system pressurized to tell if there are any leaks.