cyl 2 soot fouling and bubbling in coolant tank

[Wizard]

This begun with gentle slow bubbling (just one bubble at a time, bub, bub! at hot idle) and cylinder 2 kept fouling dry soot. Last plugs I swapped out did this on cyl 2 in 2004 before I changed manifold gasket and repaired the carb.

Last picture is a bathtub pistons and this is 1987 2.2L carb in voyager caravan, for some reason head got replaced at one point long ago with fast burn head.

Comments?

Pics as promised:











Cheers, Wizard

[NAJ]

The only thing that will cause "Bubbles" in the Cooling System is if you are pushing Exhast Gases into the Cooling System.
I would have the Cylinder Head checked for Cracks and/or Warpage.

[Wizard]

Um, carb is working properly, no vacuum/manifold leaks and I understand
that cylinder #2 carbon fouling (soot) is caused by poor compression:

Valves train not workng correctly.
Headgasket leaking under combustion pressures.
Valve seats leaky.
Cracked head.
broken ring. (??)

Compression test was done and all cylinders is even (165 PSI appox) in 2004, also had cyl 2 fouling before manifold gasket replaced.

Is this possible to have good compression with broken top ring in that cylinder 2?

Thoughts?

Cheers, Wizard

[NAJ]

Head or Head Gasket problem at the Water Jacket will cause the Bubbles in the coolant without affecting Compression.Usually Coolant burning will "Clean" the Cylinder,you may have multiple problems.If the Head was not already off I would recommend you run a Cylinder Leak Down Test but since it is apart I would still recommend you have the Head Checked.
With Compression Readings of 165 across the board I do not think you have a Ring Problem.If an Oil Ring was a problem Compression would not be affected but you would see Smoke and an Oil Fouled Plug.
The Carbon Fouling may be caused by a Basic Secondary Ignition Problem.
You have to start with the Head,if the problem is there and you reassemble as is you are right back where you started.

[Wizard]

Plugs, ingition etc were changed 2x, same results. Once on bosch, then mopar.
The wear on the terminals in the distributor is good, no cross fires, and no misses. Seems as it is firing but not combusting well in cyl 2, as seems as it's choked with too much exhaust causing the burn to be sooty?

Kinda mysterious. The manifolds were planed flat and with new manifold gasket in 2004 after compression check.

Cheers, Wizard

[NAJ]

You seem to have eliminated all possible Basic problems,my next step would be as i said,get the Head Checked,otherwise it is just a guessing game.

[Wizard]

Well the update is this both heads have worn valve guides, cracks between valves, and a big pit in the combustion chamber (I recongize this as casting bubble).

About the cracks between valves, I knew they should be harmless but I asked for pressure test but I wasn't not sure of their response so I'll confirm again tomorrow morning with my mechanic.

Mechanic also supposedly explained that one blackened combustion chamber is caused by oil leaking past the worn guides that gave the dry black soot coating. It is not rings that causes things wet with oil instead of dry black soot. So I'm still uncertain because lot of info is kinda against this one mechanic.

Cheers, Wizard