Tazzie

[Tazzie]

Can some one help me , I have a perkins 4236 with over heating problems. Motored from Tin Can Bay to Bundaberg (approx 80nm ) engine ran all day without a problem . 5 nm south of Burnett Heads engine overheated to a point of melting waterlock , Engine was shut down immediately , no damage. Pulled off all salt water cooling lines , opened sea chest no blockages. There was little water in fresh water system . Checked oil sump,does not appear to be any water in oil. Waters going some where . My theory, hole in tube stack and fresh water slowly being pushed out of engine via salt water discharge. I took the boat for a run (making sure header tank was full) and it ran well for 2 hrs and then started to overheat. This would support my theory. I was able to manage the overheating by keeping revs down. I found that when revs were down (1000rpm) temp would drop, when I pushed it up to 1200-1400 revs temp started to climb. Once temp started to climb I noticed no water coming out of discharge/exaust, once temp dropped it started pumping water again. Once engine cooled down I found water level in header tank very low again. Impeller in salt water pump (jabsco) has just been replaced. Any input would be appreciated Tazzie

[MARINE ENGINNER]

Originally Posted by Tazzie

Can some one help me , I have a perkins 4236 with over heating problems. Motored from Tin Can Bay to Bundaberg (approx 80nm ) engine ran all day without a problem . 5 nm south of Burnett Heads engine overheated to a point of melting waterlock , Engine was shut down immediately , no damage. Pulled off all salt water cooling lines , opened sea chest no blockages. There was little water in fresh water system . Checked oil sump,does not appear to be any water in oil. Waters going some where . My theory, hole in tube stack and fresh water slowly being pushed out of engine via salt water discharge. I took the boat for a run (making sure header tank was full) and it ran well for 2 hrs and then started to overheat. This would support my theory. I was able to manage the overheating by keeping revs down. I found that when revs were down (1000rpm) temp would drop, when I pushed it up to 1200-1400 revs temp started to climb. Once temp started to climb I noticed no water coming out of discharge/exaust, once temp dropped it started pumping water again. Once engine cooled down I found water level in header tank very low again. Impeller in salt water pump (jabsco) has just been replaced. Any input would be appreciated Tazzie

dear tazzie
there is a possibility to have a leakage in your cooler as you mention.
have you changed cooling water recently? maybe you have air in your system or stuck thermostatic valve but you mention also that there is no water coming out from exhaust which means broken impeller or impeller bush is slipping at higher rev than 1000 rpm
have you made any other major works on your engine recently?

M.E

[DavidLGCrawford]

It sounds like the water pump is failing at higher rpms. This causes the overheating, and then you loose your fresh water. Check bushings, belts, etc. for slippage at high rpm.

I think your low fresh water is a result of the overheating, not a cause of it.

[Tazzie]

Thanks guys for input , I had considered thermostat, I'm told by a marine mechanic that if fresh water pump has no leakage, bearing noise or excessive movement that there should not be any issues. I have just replaced impeller (Raw water ) 2 weeks ago , one would hope that it is working correctly , however worth looking again Thanks again Tazzie

[Tayana42]

Tazzie, I had a similar problem on my Yanmar, over heating and freshwater coolant missing. Eventually discovered a pinhole leak in hose to hot water heater. It leaked such a small spray that it mostly atomized and was hard to see. I had a spare anchor line stored just below the leak which caught enough antifreeze to discolor revealing the leak.

[Amnesia II]

Having just replaced my fresh water coolant i had issues refilling the system...probably due to long hoses to waterheater....I overcame that OK but later when running the motor to check temp it climbed right up and set off the alarm!

I stopped short of pulling the raw water impellor out to first check the seawater inlet where I found a small amount of seaweed....removed it and all is fine!

Do check that skin fitting is'nt partly blocked...reducing flow.

My experience in Galapagos of engine overheating....strainer checked out clear but the skinfitting was entirely blocked by a blowfish stuck inside tight as a wedge, invisible from under the boat and looking down inside the strainer. Took a long smelly time to sort out!!!

[Tazzie]

Tayana42, I would have thought if I had a leak as you suggest from a pinhole in a cooling hose, given the short time that I lost the coolant there would surely be some evidence but, something I hadn't thought of , its worth a check after I get the motor back together. I am having tube stack from heat exchanger pressure tested as we speak. I am hopeful that this is the culprit.

[Tazzie]

Amnesia II, Have flush tested salt water system from intake to out let , no probs there. If pressure test doesn't reveal any thing I'll look at overhauling saltwater impeller pump.

[Dhillen]

Tazzie,

We had the same engine with the same issues on our last boat. The coolant kept mysteriously "disappearing" and this was as we were going up the Red Sea. I finally figured out it was a blown head gasket. We were marooned in Massawa, Eritrea (one of the world's poorest countries) for a month as I shipped in a new head gasket kit. With the help of several kindly cruisers in the anchorage with us we were able to remove the top of the engine block, clean everything and put the new gaskets on. Tightening the bolts in the correct order to the correct torque with my new $150 torque wrench purchased in the country was another thing to get right.

This was all done at anchor, in 90-100 degree heat, and with "loose bowels." Loads of fun.

I hope your case will not be so dramatic but it is possible this could be your problem.

Good luck.

Dhillen

[Tazzie]

Dhillen, Just had tube stack in heat exchanger tested all good there , its starting to look like a buggered head or head gasket , hopefully a couple of pressure tests will answer this question , hopefully a head gasket .Im also told that if i run engine with food dye in fresh water that should reveal where the water is going, all the best Tazzie

[RaymondR]

One of the indicators of a blown head gasket is continuous bubbling in the coolant in the header tank. Run the engine with the header tank cap off and watch for bubbles with a torch.