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M50 heat exchanger on 5432?

rwthomas1

Sustaining Partner
I am looking to replace the older heat exchanger on my 5432. I know there is a replacement/upgrade to a 3" unit from the newer M40 model but I am wondering if a heat exchanger from an M50 will fit? According to my research the M40 unit is 3"x13" and the M50 unit is 3"x17". I can check the length but what I cannot see from the pics is the inlet/outlet configuration. Has anyone done this? Any ideas? Thanks, RT
 

tdtrimmer

Member II
5432 Heat Exchanger

I replaced the 2 inch heat exchanger with the 3 X13 inch unit five years ago. I had spent hours tracing the cooling system to determine why my 5432 was overheating but to little avail. When I replaced the heat exchanger, the problem was solved immediately. I sail the Great Lakes and find the engine rarely heats to over 170 degrees even under heavy load. I would be concerned that the 17 inch unit would provide too much cooling capacity thus not allowing the engine to reach proper heat. As I recall, the ports on the heat exchanger were placed appropriately for easy connection.

I also rerouted the water heater hoses so they now connect to the thermostat overflow rather than the heat exchanger. This change as been discussed on this list as the proper way to connect the water heater and eliminates the problem of an air lock preventing the flow of cooling water.

Tom S/V Mistress
1981 E38
 

rwthomas1

Sustaining Partner
Thanks for the input on the 3x13 unit. Its a good bit cheaper than the M50 part too. There is really no worry about "overcooling" Its not really possible. The thermostat controls the temperature of the engine with the coolant circulation. It directs coolant to the heat exchanger based on temperature and doesn't know or care how large the heat exchanger is.

All adding a larger heat exchanger will do is add more capacity to remove heat so even if the raw water circuit was inefficient it would be a long time before it was a problem.

RT
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Excess Heat

Adding to the info from RT, if you add even more "cooling capacity" like I did when I plumbed in a Heatercraft cabin heating unit, you can really shut down the thermostat at idle speed.
Here is their URL:
http://www.heatercraft.com/Category.aspx?CategoryID=37

At cruising speed, about 2400 rpm, our M25XP 3 cylinder puts out an amazing amount of heat on the "low" fan setting, and we never use medium or high. Amp draw is a bit over 4, but the engine is running anyway for this device to provide heat.

This will not change your need for the right size engine heat exchanger, I admit. Our "later model" M25 has the 3" size, BTW.

In related news, sort of, one time many years ago I had the radiator fan switch die on my Honda civic on a hot August day in heavy traffic.... got home without overheating the engine by running the car heater on high with all windows open! Boy did I sweat! :devil:

No great lesson, except that engine heat can be shed in more than one way.

Cheers,
Loren
:)
 
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