AQ140A Overheating Grrr

[samham00]

Hello, i have a aq140a with 280 drive in a guardian 18ft half cabin.
I have read a lot about these topics and the forum has been very helpful. But im still stuck so after some personalized advice please!

The engine overheated and blew its coolant out the overflow the other day. We let it cool but could only go about few hundred meters from cold to overheating.

Im not sure if its coincidence or not, but 5 minutes before overheating we became beached and the cooling system sucked up A LOT of sand.

Since then I have fully dismantled and flushed the sea water cooling side if things (including heat exchanger), checked impeller, oil cooler, manifold. Checked the thermostat, checked compression (all readings the same and high),

The motor still runs like a dream but quickly overheats at idle when run up from large bucket at home.

Water does come out the exhaust but im unsure what the flow should be like.
Could the impeller housing be worn from the sand? (it looks fine).

Can anyone offer some help please, i havnt found any workshops near me that are even willing to tackle this old girl. Pics available!

 

[Bondo]

Re: AQ140A Overheating Grrr

checked impeller

Ayuh,... Impellers are Changed, not checked....

Yes, if the housing is scored at All, it probably needs changing as well...

 

[Don S]

Re: AQ140A Overheating Grrr

When you "Checked" the impeller, did all the vains straighten out??? They should have, or the impeller is no good. Bet you didn't replace the cover plate gasket either. All it takes is an air leak in the intake side of the pump and the pump will suck air not water.
Have a look on the drive where the water hose attaches to the drive. That hose connector has a tendency to corrode away and suck air.

 

[GLENN M]

Re: AQ140A Overheating Grrr

when you sucked it full of sand,are we talking lots if so replace pump and all related parts.i mean if it worked fine before sand.its gotta be related.something could be full of sand plugging it but if that's the case your pump had to get it up there so it'll need replacing.and system flushed.

 

[Brucetafer]

Re: AQ140A Overheating Grrr

if you have the heat exchanger, and you sucked anything up there, they get clogged pretty easily... i didnt even know mine was clogged until i pulled mine, the funny thing is mine wasnt overheating...

 

[samham00]

Re: AQ140A Overheating Grrr

Hi guys thanks for your responses.

I have a spare impeller and have tried that, and the old one really does look in perfect shape (nice and straight).

I didnt replace the gasket on pump housing but it is good and sealing i think, the stern drive intake hose is a bit corroded around ends so will be checking that for sure.

Yes the heat exchanger was full of sand and i have thoroughly cleaned it and all the seawater system.

UPDATE: I took it down the boat ramp today for a in the water test. When I started to remove the cap on the seawater cooling system there was a lot of pressure there, does that mean the system is pumping fine ( or a blockage in outlet side)?
BUT yes it overheated after about 5 mins at idle, im stumped now

 

[GLENN M]

Re: AQ140A Overheating Grrr

blockage,hook up muffs turn hose on water should flow through system,start disconnecting hoses till you find point where it stops flowing,try back flushing.for it to over heat that fast at idle heat exchanger must still be plugged.that's a lot of sand to have sucked up its as you no very abrasive,and if it was mud very hard packing.good luck and keep looking there is only so many hiding places eliminate one at a time.

 

[Don S]

Re: AQ140A Overheating Grrr

,hook up muffs turn hose on water should flow through system,start disconnecting hoses till you find point where it stops flowing,

You've never seen a Volvo 140 before have you? They do not have a bunch of hoses you can just remove to check, and hooking the muffs up and getting flow through the cooling system is just not going to happen. Sounds good, but it just won't work.

Samham00
When you run the engine, you might try feeling the rubber hose that connects the manifold to the exhaust tube going to the transom shield and see if it gets hot. If it does, you don't have water flow, if it stays cool, the problem is not the raw water cooling side of the system.
since you have water pressure at the sea water strainer, then the system up to the sea strainer is good. On the oil cooler, there should be a petcock for draining at the bottom of the cooler, open it or remove it and start the engine again and see if water squirts out there. If it does, your system is good up to there. Then go to the exhaust manifold, there should be a petcock at the bottom aft part of the manifold. Do the same test there to see if you have water pressure there. If you do, then the most likely cause is the small water outlets in the exhaust manifold where the hose is that hooks the manifold to the exhaust tube going to the transom may be partially plugged up.
When you run the engine, you might try feeling that rubber hose that connects the manifold to the exhaust tube to the transom shield and see if it gets hot. If it does, you don't have water flow, if it stays cool, the problem is not the raw water cooling side of the system.

 

[samham00]

Re: AQ140A Overheating Grrr

Thanks for the help again.
I tested the two petcocks and the temp of exaust bellows and there was lots of pressure and temp was coolish.
That got me thinking the seawater system is fine. The problem must be in the coolant system.
So even though i have read on here you should not, i took the thermostat out and ran without. Engine didnt even reach operating temp after 10 mins!
Sooo my theory is, system got clogged with sand, overheated, and ruined thermostat (that i had checked, but with bad advice from friend)

Im getting new one today and should be out in boat today thanks for help again..

 

[captmello]

Re: AQ140A Overheating Grrr

Great thread, make sure you update.

 

[samham00]

Re: AQ140A Overheating Grrr

Well, I just ran up the motor with thermostat in, it overheated within 3mins, what is going on????

I then took the thermostat out and ran the motor for 15mins and no overheating...

I then checked thermostat in boiling water and it worked..

BTW im using a 88 deg c thermo for a volvo b21, the volvo penta spec thermo is 82 deg c, could this little difference be responsible?

Any help here anyone, there must be a logical reason for this...:facepalm:

 

[Don S]

Re: AQ140A Overheating Grrr

Are you sure you put the thermostat in the correct way? Spring into the block.