volvo MD7A

[jouet 820]

Hi all I have a overheating volvo md7a raw water cooled diesel engine. I removed the thermostat and disconnected the exhaust pipe from the manifold, then attached a hose pipe to the pipe that leaves the water pump and goes to the thermostat housing ,blocked the thermostat bypass and turned on the water and nothing came out of the manifold am I doing something wrong? are the waterways totally blocked ?

[Hampus]

Hey!

I'm pretty sure you won't have any water flowing through unless the engine is running, or at least turning. Have you changed the impeller? Peices of a broken impeller could otherwise clog the water canals.

/Hampus

[jouet 820]

Originally Posted by Hampus

Hey!

I'm pretty sure you won't have any water flowing through unless the engine is running, or at least turning. Have you changed the impeller? Peices of a broken impeller could otherwise clog the water canals.

/Hampus

I have bypassed the raw water pump with the hose pipe so i don't think i need the engine running.

[Hampus]

I've never fiddled with a raw water cooled engine, but when I flush out my freshwater cooled Yanmar, I need to keep it running while flushing, otherwise there just seems to be some old dirt still there the next time I start it, even if the water came out crystal clear during the flushing.

[oldsalt_1942]

The best thing about Volvo marine engines is that they make pretty good dinghy mooring anchors when degreased properly.

[Chief Engineer]

First....what symptoms did you have of overheating.

This is important because sometimes what we "think" is overheating isn't.

BTW this forum should be used to help....if you want to snipe....Join the Army.

[Sandero]

I have an MD17D which has been running nicely for 22 years.

[bmartinsen]

I'm no expert but I had a MD17 for 5yrs( still do, just not in the boat) which was raw water cooled. I believe your test would work. I think from the input to the manifold water then circulates around the cylinders before leaving via the exhaust. You probably have plugged channels thru block. You will probably need to disassemble it.
Good luck
BtW I would still have this engine if I lived closer to a volvo dealer as it was over 20yrs old and starting to get questionable for cruising remote locations it was easier to replace (new volvo D2-40)than overhaul here in Cayman where costs are high and quality ????

[jouet 820]

Originally Posted by Chief Engineer

First....what symptoms did you have of overheating.

This is important because sometimes what we "think" is overheating isn't.

BTW this forum should be used to help....if you want to snipe....Join the Army.

The symptoms of the overheat was the buzzer on, in the red very small amount of water out the exhaust and takes a couple of hours to cool down.

[Fishspearit]

Possibly a carboned up exhaust manifold? Sounds like you've already unbolted everything attached to it. When my old volvo salt water cooled engine started overheating and moving less water that was the culprit, but admittedly, I had been using it for a lot of charging.

[jouet 820]

I Think I will Start looking for gaskets

[bobnlesley]

Doing what you report should have resulted in water flow through an MD7A; I would agree that it sounds like blocked waterways in the cooling manifold.
If you're careful when removing the manifold, the gasket can be salvaged and re-used; I'm sure that your local Volvo Agent would disagree as do those here in the UK, but they'd like to sell you a new one - they're seriously expensive (about £40+VAT here)

[jouet 820]

Hi all and thanks for your posts. I removed the manifold and found it to be totally blocked especially the pipe from the pump to manifold. I cleaned it all out and tested it,I ran it for two hours flat out under load and no problems

[Chief Engineer]

Good show!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:v iking:

[delmag]

were you able to re-use the gaskets??? or, did you have to buy new ones?