Viscount
Member
What's the best way of flushing the cooling system on AD31. I am about to change the thermostats after 8 years of ownership and thought I should also do the coolant. Thanks for any advice.
AD31 flushing cooling
- Thread starter Viscount
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VicS
Well-known member
Just drain it and refill it with fresh 50% antifreeze mixture. I'd do it more frequently than 8 years I think! Every 2 years perhaps assuming its not a long life OAT type of antifreeze
Flush with fresh water then drain again and refill if you must.
Drain cocks/plugs I believe on the exhaust manifold, cylinder block and heat exchanger.
If you are in a hard water area there is some merit in buying the antifreeze ready diluted or diluting with distilled or demineralised water
Why change the thermostats? Do you have a problem with the temperature or are you just fixing something that is not broken?
Flush with fresh water then drain again and refill if you must.
Drain cocks/plugs I believe on the exhaust manifold, cylinder block and heat exchanger.
If you are in a hard water area there is some merit in buying the antifreeze ready diluted or diluting with distilled or demineralised water
Why change the thermostats? Do you have a problem with the temperature or are you just fixing something that is not broken?
Viscount
Member
The coolant has been changed a couple of times in 8 years, it's just the 'stats that haven't. I've had a couple of apparent overheating issues in as much as the gauges have gone to about 220F although the warning lights have never come on. The overheating seems a bit random - e.g. I've run at WOT for 30 minutes without a problem. Next time out, usual 3,000 RPM cruising can see gauges getting higher than they should and this was immediately after anti-fouling so it's not that. I just wondered therefore if the 'stats were intermittently not opening fully.
VicS
Well-known member
Fair enough.
Certainly worth checking the thermostats. IIRC they should just start to open at 81C .. they are probably marked but the manual should tell you. I dont know the temperature at which they should be fully open.. it may also be marked on them.
I'd also check the whole cooling system esp the raw water side of it.
Heat exchanger clean?
Water intakes and strainer clear?
Hoses OK internally?
Pump impeller OK?
Pump not excessively worn?
Water discharge to the exhaust not obstructed?
rlw
Member
Hi,
From experience before you start buy an IR temperature gun to measure the temp on the engine before you start. I had AD41's in 2 boats over 10 years and wasted a lot of time on temp issues that were not there. Corrosion on the wires can give high readings. I once shut down an engine after banging of a wave and seeing the temp spike. In the end it was just a spade connector that slipped in the dash. Pushed it back and temp back to normal.
With the IR gun you can determine whether it is an electrical gremlin or a real problem.
Good luck
Rob
From experience before you start buy an IR temperature gun to measure the temp on the engine before you start. I had AD41's in 2 boats over 10 years and wasted a lot of time on temp issues that were not there. Corrosion on the wires can give high readings. I once shut down an engine after banging of a wave and seeing the temp spike. In the end it was just a spade connector that slipped in the dash. Pushed it back and temp back to normal.
With the IR gun you can determine whether it is an electrical gremlin or a real problem.
Good luck
Rob
Viscount
Member
Thanks guys, hoping to get to it this week-end.
