Volvo MD2B : lost compression in 1 cylinder

[Cheechako]

My MD2B was a great engine, but I often heard they are a bear to work on or rebuild. All kinds of litle idiosyncrasies to deal with.... goood luck. Do you have the workshop manual?

[dubhouse]

Ok. Just had to bend the oil pipe a bit to get the head off. My suspicions were correct . Blown head gasket. The reason no water in the oil was that the jackets were dry and not getting any water to begin with, thus the extra heat and blowing the head gasket.

So obviously I need a new head gasket but I'm still trying to figure out the exact water flow path through this engine. As you can see in the pictures the passageways are very corroded and blocked. Most of the blockage however is in the exhaust manifold water supply passages.

I'm thinking of soaking the exhaust manifold in descaler. I'm not sure exactly how to deal with the head and cylinder passageways though. I'd rather not have to take off the cylinder block but also don't want to drop a bunch of crud down in there the cylinder.

Or should I just bit the bullet and take these parts to a machine shop to get them resurfaced or something ?

[Cheechako]

you've gone this far, pull the other head, clean the block out, and replace both gaskets! maybe a machine shop will boil out those heads?

[dubhouse]

What exactly does "boil out" mean ? Do they literally boil them in water or something ? Do they use chemicals at all ? What I really need "boiled out" is the exhaust manifold.

[model 10]

"Boil out" is an old term used when they would put the part in a tank of hot solvent and it would disolve carbon. Now days they mostly use more sophisticated spray booths. If all you need is some scale removed from the exh manifold a radiator shop could do it or you could use a screwdriver and poke it out, You could get it bead blasted too.

[bobconnie]

At least get a shop to ck the heads for warpage. No sence putting new gaskets on warped heads! while there get em bead blasted to remove the scale. Just my 2 cents

[dubhouse]

It doesn't seem like any local shops do boil outs. I wonder if I soaking in muriatic acid would do the trick. If not soaking, at least filling up the clogged pathways with the stuff and letting it sit.

Does anybody know how to do a boil out ?
I looked up bead blasting but I couldn't find anybody in the area either. And I'm in los angeles county !

I'm taking the head to a shop today.

[poboy]

Soak the head and manifold in muriatic acid diluted at least 50% with water. Available at Home Depot or Lowes, usually in the paint section. Will foam sizzle and bubble as it dissolves the salt and scale blocking the passages. Had to do several times on a couple of MD7As I rebuilt. Be sure to neutralize the acid with a thorough water wash down.
When you put it all back together, hook up a 12 volt pump and circulate a fresh batch of the solution through the block for an hour or two. This will clean the passages in the block.
Hook the intake side of the pump to a hose that goes to the bucket. The output side goes to the raw water intake on the engine (after the raw water pump). Then run a hose from the raw water output on the exhaust manifold back to the bucket to complete the circuit. Don't forget to remove the thermostat for this process. When done, flush well with fresh water and replace the thermostat. I do this once a year with my raw water cooled Volvos and have not had an over heating problem since adding this to my maintenance schedule.