Overheating AQ125B

[Eric Gutierrez]

Hi All can someone help me out,

I have a Volvo Penta AQ125B and is overheating after start up. Iv replaced the sea water impeller and Circulation pump with same results.

 

[alldodge]

Tells us a bit more about what lead up to the overheating. How long has it been doing the overheat?

 

[Grub54891]

Replace the thermostat.

 

[jerryjerry05]

DON'T replace the thermo.
​The thermo's in antifreeze and is usually not a problem.
Never had to replaced one.

Look at the exhaust manifold.
They can look new and still be bad.
The heat exchanger can get filled with sand and crud and cause an overheat,
Those are 2 of the biggest problems.
Another is the excentric cam in the water pump.
Over time it wears out and enough water doesn't get pumped at higher speeds.

The manifold, remove the rubber bellows, you'll have to loosen the manifold.
Check the exhaust ports on the end of the manifold.
There are holes around the end of the manifold they get clogged with rust and crud and cause overheating.
There usually is no cleaning or fixing these.Replace.

The heat exchanger is in the fresh water side of the resivoir
It has a drain on the bottom of the housing try taking out the plug and see if it drains.
It should drain water.

Look up a parts diagram and see where the different parts are according to your year/ model.

 

[Grub54891]

Any time an engine overheats, the thermostat is compromised. I agree that cleaning the heat exchangers should be done also.

 

[jerryjerry05]

He's not replied so he might have it fixed???
I seriously doubt he's done any damage to the thermos.
Overheating would damage the pistons and rings.
He's already wasted $ on a circulation pump.
​He needs to figure out the problem not throw parts at it.
These 4cyl.Volvos are VERY expensive to buy parts.
Thermo $37
The exchanger insert is $1300
And the manifold from Volvo is $1500 luckily that can be bought aftermarket.

IF??? he can get the insert out he might be able to get it flushed at a radiator shop???

 

[bruceb58]

Very common on those drives for the fitting where the hose connects to the drive to corrode away and cause an air leak and this causes the raw pump to lose prime. Make sure you check that fitting.

Typically it won't overheat at idle since this fitting is underwater. If you are experiencing this at speeds above idle, it is worth a check.

 

[Mullin]

Its really common to have air leaks in the outdrive that causes the overheating. You can connect a hose up top behind the motor and backflush it to see where the leak is.

 

[bruceb58]

Is it overheating only on muffs? If so, did you plug the hole in the nose cone of the drive?