250S M108 Clooged coolant in cylinder head?

[karshack]

So my 1967 250S started doing the "Puff" the magic dragon impression a couple of weeks ago. My machinist says that there could have been a coolant system problem to cause the pitting or divot at Cyl 5 -- wrong coolant, not enough, not changed in ages, etc.

So taking an extra look at the head, I noticed that there are several of the large coolant passages that appear to have nearly smooth ivory colored interiors and holes (larger than pinholes) that continue into the passages.

I took a screwdriver to poke at one of the passages and the ivory substance gave way to reveal the cast passage. The substance gave way like the foil caps on medicine bottles. I checked all of these seemingly blocked holes with the holes in the head gasket. All holes align. That is leading me to think that years of poor coolant history has clogged up needed coolant passages in the head and finally forced an overheat situation.

Tell me what you think. I am prone to go ahead and poke these passages clear. I've had the car for 2 years and it is a daily driver - about 15 miles, city and freeway, on weekdays. Very nice at 65-70mph.

[karshack]

Well, impatient me just had to get started before any replies. This is/was my daily driver and I'm trying to get it back on the road pronto. So, I've found out that those coolant passages had aluminum insert caps.

So, don't understand why 9 passages (holes in head are 18mm) would be blocked. Again, all of those 9 passage holes have corresponding holes in the head gasket (Elring 826 464). The aluminum caps look too professional for a diy job. And now I'm wondering if the pinholes in the caps were made be the shear heat/pressure of the coolant trying to get into and through the head from the block.

Thanks in advance.

[Coolvibes]

So there are corresponding coolant passages in the head, gasket, and block, but it looks like some of them were deliberately partially blocked off?

[cth350]

photo? -cth

[karshack]

Coolvibes - Yes, there are 9 of these large coolant passages. All had been plugged up; but some of the plugs, that I suspect are aluminum, had holes. At first I thought it was sediment that had become smooth over time and heat. But after I decided to attack them I realized they were man-made and put there on purpose - or mistakenly left on/in. I'll try and post a pic when I get home.

The reason that was willing to take an action that might damage the head is my machinist said that he could not rehabilitate it because someone had machined too much off on a previous head job. So my head is too thin. Now I'm thinking that between my no/low flow situation and the fact that the bolt torquing failed -- maybe something was just waiting to go "puff". I filled the divot in with JB Weld yesterday, and cleaned up the head. Now I need to clean the pistons and cyl bores, and get a broken banjo bolt for the water pump breather removed and replaced.

Over and out for now. Thx

[karshack]

Reading is fundamental. Found my MBZ engine parts catalog for Type M108 (Catalog 10 107). Table 2, Engine Housing items #7,8,9 are identified as "Water Distributor". Number 9 seems to be a hollow, straight through sleeve. Numbers 7 and 8 appear to be capped at the end but have a hole/opening on the side wall. I suppose this is to provide a directional aspect to the flow of water. Well, I supposed I'll have turbulent flow when I get this back together again.

My pic of the water distributor is not loading. I'll work on that tonight.