Cool/Heat: small hole seen behind thermostat

[guy]

Hello all,
I have a question related to the cooling system.
This is about a 170 OHV 6-cylinder engine.
I'm in the process to replace the water pump and add a thermostat which was missing before.
As the connection where the thermostat fits is open I could have a look to the inside if the engine there.
What I noticed is that there is a very small hole in the wall to which you look when the thermostat is removed. On one side I would say this is not normal, and is a possible explanation for the white smoke I have when starting the engine. On the other hand, the hole is nice round and pretty small which makes me think it's the intention it's there. On the picture I added you can see what I mean.
My question now is if this is normal or not. If not, can somebody give some guidance on how to repair? Does a kind of metal paste exist which I can put on it to close it?



thanks already for any advice,
Guy

[StudeRich]

If you notice there is a bleed hole in the mounting surface of the Water Pump, yours appears a bit clogged but it is there for a reason.

But the one you refer to in the Cyl. Head does not look good, more cleaning of all that crud may help to see what is going on, I would not think that wall is that thin, but it appears to be an air bubble in the Casting or a sand mold wire hole that definitely should not be there.

[jg61hawk]

Is there a crack in the flange UNDER THE THERMOSTAT housing flange? Is there water in the oil? I don't know what's under the hole if it is just more coolant passages you're probably fine...if it's an oil galley then not so fine. Perhaps Bob Palma will show up here.

[jg61hawk]

This is a bump....someone must know what is behind this hole. Help this guy 11 posts....get going!@

[BobPalma]

Yes, the rough-shaped "hole" seen behind the thermostat area in the second (right-side) photo does not look good. .

I would clean that area thoroughly and see if you can blow air into that crack/hole, or otherwise determine if it is open on the backside, as well as what can be seen. The head may indeed be cracked in that area.

If you get it real clean, you might be able to smear some JB Weld into, over, and around it to get it to seal...but if you are having white smoke out the exhaust and losing coolant, you'd better remove the head, have it checked for cracks, and then repaired if needed. BP

[(S)]

I think the hole leads to door number one: the #1 intake port..... (probably why you have white smoke.)

[guy]

Hello all, many thanks already on the replies I got. In the meantime I tried to determine how deep that hole is by putting a small needle in it. I must say I couldn't put it far in it and on what I could feel is that I was really at the bottom. What I did is putting something like metal paste to it to have it closed.
Another point is that the smoke is mainly when I start the engine. Once I start driving he stops smoking. even when I stop and let run the engine stationary. If I'm really loosing coolant through that hole I would expect to see a constant white smoke, even when driving (I may be wrong here, I'm not that a specialist).

Further on I must say that I don't have a real loss of coolant. Now, through such a small hole I can imagine it takes really long before you really notice.

Nevertheless, checking the head for cracks is for sure something I have to do somewhere in the future. But as I don't have a spare head gasket I currently prefer to keep that part closed. One step at a time an at a money

[Dan Timberlake]

White smoke on start up can be normal exhaust condensation at least on a cool day.

Tough call based on symptoms.

I'd probably do a little grinding for cleanliness/roughness and apply a patch of a non 5 minute epoxy/JB Weld.

Pressurizing the cooling system >>might<< help judge if that is a surface casting flaw, or indeed leads to trouble. A cooling system that does not hold 10-15 psi pressure could have any number of other leaks though.

I might try to pressurize the intake (carb off, manifold flange blocked off, rockers backed off, etc) to close all valves) , and spray soapy water on the flaw. If it does not bubble at 10 or 15 psi manifold pressure I'd use it as-is.

drilling and tapping 1/8 inch pipe (or some smaller size straight thread with Loctite) could seal it, but would certainly put chips into the intake port, it that is what lurks behind.

[Dwain G.]

Had a chance to look at a bare head. The exhaust port for No. 1 cylinder is directly on the other side of that pin hole. The coolant can be tested for exhaust contamination with a block tester kit. I think some auto parts stores have these for loan, you only have to buy the liquid.