4.3 Overheating over 3000 rpm Starboard side hot at idle

[Eric Bornstein]

Started having overheating problems over 3000 rpm last season. I have changed the impeller, old one was intact. I removed and cleaned the manifolds and risers, some rust. Checked the timing, OK. Runs in fresh water. Running on muffs today at idle I found that the starboard riser was hot 115f and the port side was cold 60f. Hoses running into the riser measured 60 and 80. At the stern drive the starboard flow is less than the port side and is the exit water is hot, port side is cold. Removed the freeze drains from the risers and the flow seemed the same on each side. Starboard manifold measured with a gun is 136 at the rear 125 middle and 118 at the front. Port manifold is 110 to 85. I hear clicking sounds. flappers? they were free when I cleaned the manifolds. Cleaned the thermostat housing, it was OK, and checked the thermostat in hot water and it opened at the correct temperature. Seems like a restriction, but were do I look?

 

[Bondo]

Ayuh,.... Welcome Aboard,..... Manifolds Never run the same temps, 'n yer's ain't all that hot,.....

I don't see a problem,....

'n, Ya, the clickin' is probably the shutters, they'll do that when the rubber edge burns off,.....

 

[Watermann]

My 4.3L exhaust elbows on muffs I found swap between sides which one is warm to the touch but the risers never feel warm let alone hot. So what is the overheat temp and is that with the gauge or IR gun on the T stat housing? What is the T stat temp, the 140 0r 160?

The water from the relief ports comes from the Y pipe, they aren't separate so one side always seems to have more or less exiting.

 

[Eric Bornstein]

Don't remember the thermostat temp, it was last year when I checked it. My temp gauge is not marked in degrees, it does run inn the normal zone at revs below 3000. At 3000 it comes close to the red zone and as the revs increase so does the temp into the red zone. Slowing down causes an immediate drop back to normal. I didn't have the temp gun with me at the time (on the water) but will bring it next time. I will check the t stat housing on the muffs with the gun soon. When the thermostat opens where does the flow go, to the manifolds or the risers? I will try a clear hose on the line between the transom and the power steering cooler and look for restrictions at the transom at the same time. Could the extreme differences between the sides be because of the ball and spring devices in the cooling lines? Wife's birthday today so I will have to put off checking till tomorrow!


'85 Doral Cavalier 21' 4.3l V6

 

[Watermann]

The fittings on the T stat go to the manifolds, the seawater comes into the PS pump then to the fittings in front of the T stat which go to the risers. here's a pic of my 4.3LX, it's a 1988 model year motor. Not sure what year yours is so they may look a bit different.

 

[Stamey]

I had a similar problem with my 1982 305. Happened just like you describe, port manifold hotter than the other and temp gauge rising at speed but OK at idle. We figured it was a restriction and crimped the hose going to the elbow for that manifold with vise grips. Then I ran it down the lake for a a little ways. It blew the hose going to the bottom of the manifold, confirming the restriction. After hose and manifolds replaced, the engine would overheat whenever I was in a no wake zone but would drop to 160 as soon as I sped up. This turned out to be the balls and rod in my water neck being MIA, likely by a previous owner trying to fix the other overheat problem. Installed the balls and the cooling system worked perfectly.


Chris