Possible blown head gasket, overheating, P.O.S. 1985 merc 170 with closed cooling-gctid405193

bhawes wrote:
Here are 2 gaskets and a stainless plate between the manifold and riser. First a gasket, then the plate, then the other gasket. The stainmless plate blocks off the 2 long openings in the gasket, leaving only the end opening open. I'm not sure if that's how you have it, but if not, it may be the cause of your problem.

I am missing the plate but I have 2 gaskets back to back with the holes on opposite sides, it is a temporary fix till I get a plate and find the overheating problem, that isnt the problem with overheating.

I torqued the heads when I installed them, no I didnt get them magnafluxed, no idea why the pushrods and springs were broken, it was that way when I bought it. If it wasnt for the bubbles I see coming up in the riser/radiator I would suspect something other than a head gasket, it runs perfect and being a 4 cyl wouldnt you think it would have a good miss with a loss of compression.

has anyone used the harbor freight leakdown tester, its around 40$

[bhawes]

Here are 2 gaskets and a stainless plate between the manifold and riser. First a gasket, then the plate, then the other gasket. The stainmless plate blocks off the 2 long openings in the gasket, leaving only the end opening open. I'm not sure if that's how you have it, but if not, it may be the cause of your problem.

Did you have the head magnafluxed? It could be a crack in the combustion chamber, most typically between the valves. Do a leakdown test to determine which cylinder is the culprit.

Did you check the torque on the head bolts?

Did you find out why the pushrods and springs were broken?

Let us know what you find.

over the last month and a half I pulled the engine, replaced the transom assembly, pulled the head and fixed a broken push rod and a couple broken springs, got it all back together and found out I was missing a plate between the exhaust manifold and riser and thought that was why I was overheating but no it couldnt be that easy. took a break from working on it and pulled the thermostat yesterday to eliminate that, nope that wasnt it. one thing I noticed was the water in the riser/radiator got warm almost immediately then I noticed air bubbles almost like it was boiling.no water in my oil, I had good compression as soon as I assembled the engine before I ran it, I know I should recheck now. what is the best way to start isolating in a closed cooling system, any other ideas,