Mercruiser 4.2 heat exchanger/oil cooler help please.

[Mike k]

Hi I have a 2005 Mercrusier 4.2dtronic and I have today changed the pencil anode that's fits about half way up the base of the oil cooler which is a tube lying directly beneath the heat exchanger larger tube and effectively both tubes form a complete unit so I am guessing the anode protects the metals in both parts ( oil cooler and h/E) from the seawater. Normally when I change it seawater pours out until I can get the new anode and nut secured in- but today no water came out.

Anyone got any ideas why that should be ? Does a blockage sound like the cause?. I used Rydlime last year and circulated it for a few hours but recently I had to replace the seal for the cooler endplate because salty deposits were evident on the joint and I guessed that was because the Rydlime had disturbed the seal somehow. Could the Rydlime not have worked and should I be looking at removing both end plates and trying to rod straight through - can you do that without damaging anything ?

I have had no temperature problems that have been evident or alarms that have gone off but then again if its the oil cooler I am not sure if that sends an alarm if too hot anyway and if it should have sounded an alarm ... it hasn't!!

Should I be concerned ?

Any help would be greatly appreciated

Cheers

Mike


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[spannerman]

If you haven't run the engine for sometime it could have drained back down through the seawater pump, some engines begin to drain down as soon as you turn them off, and others don't, seen this on several twin installations so identical engines!
No alarm on seawater side, only on freshwater side.

 

[Mike k]

If you haven't run the engine for sometime it could have drained back down through the seawater pump, some engines begin to drain down as soon as you turn them off, and others don't, seen this on several twin installations so identical engines!
No alarm on seawater side, only on freshwater side.

thank you Spannerman

 

[davedpc]

I roded out my heat exchangers with a long threded stud [4.0 then4.2mm I think] fitted in to a low speed drill. When the end caps were removed all the lower honeycomb holes were blocked with **** where the crud settles as the engine cools. The water pump impellor on the 4.2 is massive [when compared with a 200 VP] and are therefore quite efficient

 

[Mike k]

I roded out my heat exchangers with a long threded stud [4.0 then4.2mm I think] fitted in to a low speed drill. When the end caps were removed all the lower honeycomb holes were blocked with **** where the crud settles as the engine cools. The water pump impellor on the 4.2 is massive [when compared with a 200 VP] and are therefore quite efficient

Useful info davepc thank you.Just been measuring up some braided wire to go in my cordless drill as my access isn't straight into the holes

 

[Mike k]

Just thought I would post the outcome. Having seen some of the white powder on the end caps as a tell tale sign of a slight leak and possible the outcome of a blockage decided to get on with the job. Removed the oil cooler end cap and the heat exchanger end cap and with a 22 rifle gun cleaning rod I carefully rodded every single tube and apart from two which were a midge smaller and couldn't get the rod in.As far as I can tell all were clear and no real gunk in there after 360 hours . Used the torque wrench and voila all back to normal - hopefully leak free, we shall see.