3.0 Backflush Technique

[Zewbie]

I'm wondering if there is a best practices method to backflush the raw water cooling system on the 3.0?

I swapped out a failed impeller and thought most of the broken pieces were in the housing as well as the hose leading to the thermostat housing. I ran water through the hose and cleared out the particles. However, I had it out today and once it was up to temp and the thermostat was triggered the engine cooled way down and I found the large hose going from the thermostat to the block had BURST. So, I believe I must have a blockage between the thermostat and exhaust outlet.

The manual has the water flow diagram, but I'm wondering it there is a recommended place to hook up a hose or air to flush things out? I have searched the web and forums without any good how to info.

Thanks in advance!

 

[Zewbie]

Re: 3.0 Backflush Technique

I believe I have flushed things out, but am hoping someone might be able to validate or show me if I missed something.

I wrapped duct tape around the busted hose and while it was connected to the circulating pump at the block I connected my shop vac to it. I first sucked all of the water that was in the block out and checked for pump pieces and found only one small piece. I then ran the garden hose through the thermostat housing and filled the block several times and pulled the water out with the shop vac. Seemed to flow pretty well.

I then connected my garden hose to the front of the manifold and opened up the drain screw and ran the hose flushing out any sediment - very little. I then closed the drain and allowed it to discharge through the riser and out the transom exhaust outlet - decent flow.

I pulled off the riser which had one small piece of impeller wedged in the outlet on the riser (in one of the slanted channels). I ran the hose through the water passages and then compressed air. It seems pretty clean.

Did I miss anything and is that sufficient? This post here also had that hose burst and Don and a couple others mention that maybe the hoses were in the wrong locations on the impeller pump. Based on the Volvo manual I downloaded it looks correct, however if you look at the parts diagram they are opposite (images attached).

Is it possible the hose was just weak, might there be a blockage or maybe there was one that was flushed out?

 

[CheapboatKev]

Re: 3.0 Backflush Technique

All I can offer is on my 4 cyl mercruiser..The hose burst on mine as well long after changing out my impeller.
The hoses dont last forever and must have been 20 plus years old on mine.
Sounds like you are good, run her and keep an eye on the t-stat
Good luck