Is my head gasket blown?

[rgafitanu@gmail.com]

Does it come out by unscrewing the large nut next to the head or by the bolt on the side (or that one is a drain)?

[Tyler S]

The smaller bolt on the back of the coolant jacket. It is a long through bolt that threads into the large hex collar on the head. You wont be able to completely remove the bolt because of the IP clearance. It will come out with the coolant jacket.

[rgafitanu@gmail.com]

I guess I will not be able to slide the head lateral to avoid removing the exhaust manifolds. It doesn't appear to be enough room towards the IP.

[Tyler S]

I ended up pulling mine as it frees up a lot of room. Not much left to do so. The fuel lines, bracket at the rear, and the 3 mounting bolts/nuts. Find a safe clean place for it. You will also be able to verify correct IP timing when it goes back together.
Dont forget about the 2 small allen bolts in the front of the head. One is hidden in the chain tensioner oil pool.

[rgafitanu@gmail.com]

It was way faster than I thought. Exhaust manifolds came out easy, I was able to retrieve the camshaft washer that I dropped in the chain well. I just can't see the culprit. It's obvious that there is water leaking in cylinder 4 but I can't see any corrosion, gaps or anything to make me say "Gotcha".
I will get a straight edge to check flatness and I will check valve sealing. I will probably remove the springs to check on seals, I'm trying to find the source of the rocker noise, so far rockers don't show any sign of hitting the spring.

[rgafitanu@gmail.com]

And the cylinder head.

[Tyler S]

There is quite a bit of staining on the head gasket between cyl 4 and 5. Is most likely your problem area. Carefully remove the head gasket and have a look at the other side as well as the water jackets in the block. The head gasket at the top (drivers side) water jacket of cyl 4 on your last block pic looks compromised. The corresponding water jacket in the head looks extremely enlarged/corroded

[tel76]

Check the bore carefully, a few years ago we had to replace the block due to a crack (lengthwise) in the cylinder wall.

[ja17]

You may have to have the head pressure checked.  I have seen a 250 head develop a pin hole high up in the combustion chamber of the head.  Old coolant slowly eats away at the aluminum casting until a pin hole develops, then you have a mysterious leak into the combustion chamber.

[rgafitanu@gmail.com]

I don't see anything obvious. First 2 picture show cylinders 5-4. Third picture shows the head combustion chambers 5-4. The "hole" under exhaust valve 4 is solid, maybe a plug.

[rgafitanu@gmail.com]

Next picture is the block side of the gasket at 4-5 and the last is the head side. I checked the flatness and I couldn't fit a 0.003 feeler under the straight edge but a 0.0025 did go through. I will have to clean these surfaces and get a better edge.
What can I use to clean these surfaces? Alcohol, scraper, die grinder (kidding)?
Do I have to use new head bolts?
BTW trying to get the camshaft bolt off I rotated the whole thing both CCW and CW. I know it is specifically posted not to... Why?
Compression chamber is very shallow to check for leakage by pouring gasoline.

[ja17]

Looks like a loose leaky head gasket to me. Clean up surface with solvent alcohol, brake clean or such will work fine.  .0025" warp is with-in specs. The head bolts can be re-used since they are not the "stretch type" as used in the newer cars. Be sure to clean the threads in the block and the threads of the head bolts. Lightly lube the threads and under the bolt  heads before installation. The new stock head gaskets are greatly improved with better materials and better construction. Don't forget to tighten the head after first warm-up and then at around 500mi.

[tel76]

The hole that appears to be plugged in picture # 3 should not be blocked, looking at the picture it appears to have a crack emanating from it, or is it just a mark?

[rgafitanu@gmail.com]

There are 2 "plugged" water holes corresponding to the location of the 2 water ports (one for sensor/switch and the other for heater conduit). I was thinking that the holes were deliberately plugged at these locations however, the other plugged/welded hole is flush with the surface while this one appears corroded. I will pour gas on this one too to see if it leaks.
I am also trying to find the source of the rocker noise, should I take the springs out and check the guides, bushings and rotators?

[Tyler S]

That is the area I was talking about. The hole circumfrence is enlarged/corroded and very close to the combustion chamber. I also see the crack. Unless its a piece of hair or something. Either way it needs to be cleared out for further inspection to see if it can be welded. Otherwise the head needs to be replaced. You don't know what the rest of it looks like inside.
Remove the 3 Welsh plugs that sit underneath the camshaft. Will give you a better look inside the head.

[rgafitanu@gmail.com]

I cleaned the head surface very well and here is what I found:
- the plug is corroded like a cavity but it doesn't leak anywhere
- what appeared to be a crack between the plug and the chamber is more like a ding/imprint maybe like hit with a screwdriver. It is not in the chamber but I believe that coolant made it's way in the cylinder this way (picture).
- the head measures 84.45 mm
- the flatness is under 0.003"
- there are visible milling marks (picture). I thought the surface is supposed to be of better quality. Since there is a 1/2 mm missing from the thickness, maybe the head has been machined before by inexperienced people.
- I checked all valves by pouring gasoline on them and they all appear to be leak free.

Would it be wise to weld the corroded cavity and then skim the surface to get rid of the milling traces? Or "If it ain't broke don't fix it"?
Should I take the springs and valves out to check them out? I would not want to break what appears to be a good seal valve/seat.

[Tyler S]

That is definately a crack and most likely started inside the cavity where the metal is most likely very thin. The hole being plugged up is either from combustion particulates making there way through the crack or someone at one time added "stop leak" to the system. Stop leak bungs up where high temp or oxygen is present.
Needs to go to the machine shop for evaluation and pressure check. I wouldn't worry about the valves at this point. Leave them in for the machine shop to evaluate.

[tel76]

Looking closely at picture # one I would suggest that the material that was blocking the coolant hole is corroded particles of aluminium from the cylinder head caused by not using the correct (or none at tall) antifreeze/corrosion inhibitor.

[rgafitanu@gmail.com]

Anybody knows a good machine shop in New England?

[Cees Klumper]

Are you comfortable with the condition of the engine itself? Reworking the head can reveal problems with the pistons, bearings etc. you may want to think about a rebuild by a specialist such as Metric Motors which wold be around $9,000. (I remember some years ago that was in the neighbourhood of $5,500).

[rgafitanu@gmail.com]

I was very happy with the engine. I was driving it 85 mph (137 km/h) without a sweat for the last 2 years. I had great oil pressure, the camshaft appears to be in great condition, the bearing surface look great, the rocker ball posts look OK.
I stumbled onto this because the temperature gauge was going towards 90C which wasn't happening before. And it was doing so only when stopped at lights. I thought that a 50 year old car without a coolant expansion system needs more frequent coolant level check. After 2 checks where I had to add 2 quarts each I opened the valve cover cap and pulled the dip stick to see the dreaded orange foam. That's when I put the car in the ICU and started working on it.
All the valves appear to have no leaks, the ding that Tyler is concerned about doesn't have any "out" anywhere else in other cavities. I'm not dismissing it, I am trying to find a shop that can fill that ding and the cavity if needed plus do a compression check. The only "annoying" problem that I had was a rocker noise that I am hoping to go away after inspecting all springs/valves.
I think that heated coolant got up into that corroded cavern, turned into steam since it had nowhere to go, corroded the cavity further and found it's way into the closest cylinder with the help of the ding. The gasket supports this theory, it is discolored at that bridge.
Sometimes I am inclined to put a new head gasket, put it back together and see if the problem goes away.
$9,000 will threaten my married life, I would have to wait for my Christmas and my birthday.

[rgafitanu@gmail.com]

If I were to use Permatex #2 on the oil pan gasket, should I apply on both surfaces? Leave it hours to get tacky before tightening?
About the head gasket, should I use Permatex copper or not? How? I get a good discount from the dealer, should I get the gasket from somewhere else?
Thank you all for helping.
Radu

[Benz Dr.]

I've been using Permatex  Gray which is probably your best choice.

[rgafitanu@gmail.com]

I have a machine shop welding that cavity. They will skim 0.006" to 0.008" from the head. The head has a thickness of 84.45 mm and I assume it had some machining before since stock thickness should be 85 mm. I didn't find any camshaft post shims when I took it apart. Should I add 0.008" shims or 0.028" to bring to stock? I am not changing anything else now (camshaft, valves, rockers etc).

[Benz Dr.]

I use .015'' cam shims. They may come in different sizes but that's the largest size available. I often use two shims if there's been a lot of work done or the top of the head was milled. Failure to get the the rocker geometry correct will take out all of your valve guides before you get your car out of your shop door.

 They're cheap, easy to install, and they provide good insurance against engine damage.