Unequal cooling / heating

L

LuckyPenny

Petty Officer 1st Class
Joined
Feb 21, 2003
Messages
256
This has to be a new one, it is for me. I have a 1977 Merc 5.7L, 250HP FWC. The engine great, no problems on that score. I recently replaced the spacers on the elbow, new and new gaskets. Start up and high idle. reaches normal op temp (150~) or so, the hoses to the elbow up to that point are cool, and the elbows are cool (water temp 52F) the other hoses and manifold heat up as normal. Now the problem. Once the T-Stat opens, only the port hose and elbow warm up. The starboard hose and elbow remain cool. How is this possible? The engine temp holds and there are no sighs of overheating or underheating.

Just sign me as totally confused.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Unequal cooling / heating

It's normal for one side to run warmer than the other, but it's not normal for one side to get HOT.
Get a temp gun and measure the risers and lets see what you are actually getting.
Usually (even with a difference at idle) the temps will be very close to equal when running at rpm and under load.
 
bruceb58

bruceb58

Supreme Mariner
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Mar 5, 2006
Messages
30,478
Re: Unequal cooling / heating

The way the thermostat housings are designed, a lot of the hot water leaving the engine will tend to flow toward one of the manifold hoses over the other. On my Volvo, I measure nearly 10 degrees difference at a fast idle for just the hoses, let alone the risers.
 
Scaaty

Scaaty

Vice Admiral
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May 31, 2004
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Re: Unequal cooling / heating

The water flows in one direction through the motor, not equal to both sides........
 
L

LuckyPenny

Petty Officer 1st Class
Joined
Feb 21, 2003
Messages
256
Re: Unequal cooling / heating

Thank you very much for the response. I will run her up again this afternoon, and do a dockside test in gear to see if it makes a difference.
I may be over reactive, but I am getting her to run like a top, and being very critical.
engine heat has been an issue with this engine for a long time, and over the past several months I have found things that should never have been. Now that I have restored the proper parts, in the proper place I am really getting more comfortable with her.
 
bruceb58

bruceb58

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Messages
30,478
Re: Unequal cooling / heating

Scaaty said:
The water flows in one direction through the motor, not equal to both sides........
Click to expand...

Not sure what your point is.
 
A

AaronG

Petty Officer 1st Class
Joined
Aug 22, 2004
Messages
234
Re: Unequal cooling / heating

I know on my 1997 Alpha 1, the starboard side riser is always warmer. It was that way nen when the manifolds/risers where brand new. neither get too hot. You can always comfortably rest your hand one either one.
 
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