W123 cracked head or something more nefarious? - Page 4 - PeachParts Mercedes-Benz Forum

97 SL320 · #46 03-15-2017, 05:23 PM

Quote:

Originally Posted by Maxbumpo

I'd say pull the head and then you'll know.

If you want to spend money and time doing more testing first, send an engine oil sample to a lab to test for coolant.

Testing for coolant in oil won't ID a combustion chamber to coolant leak. It also dies nothing to ID a exhaust / intake valve or piston ring not sealing.

Quote:

Originally Posted by Maxbumpo

If your other test of leaving the radiator cap off eliminates the problem, then you've pretty much narrowed it down to either a cracked head or failed headgasket.

This isn't a valid test as the pressure isn't changing much. It might slightly help coolant consumption in the early stages but there are better ways to test. ( Leakdown )

Quote:

Originally Posted by Maxbumpo

Could the head have cracked in such a way that the coolant only goes into the exhaust passage(s), so that it never enters the cylinder?

For most ( all I'd wager ) engines, the exhaust ports are surrounded by coolant. Cracks only running through the exhaust port are rare. Early 80's Ford Escort 1.6 CVH motors would crack through the floor of the port and would extend into the combustion chamber / valve seat area where a leak down test would pick it up.

Hawk8789 · #47 02-19-2018, 03:46 PM

I finally got a chance to take the head off. It was the easiest, but longest job I’ve ever done. Everything between the head and block was wet. There are no obvious cracks anywhere. The gasket looked okay, but soaked through. The pistons in 1 and 4 were caked in carbon. Cylinder 2 looked like it was washed out. The prechamber tips on 1 and 3 looked like they were caked up with calcium deposits. After starting to clean, the valves on 1 and 3 are white. I’m not sure what it’s supposed to look like after all these years, but I can’t make much sense of this with my limited experience. I haven’t seen inside cylinders 1 and 4 because I didn’t want to mess up my timing by playing around with that. Basically, the only cylinder that looks like I would expect is 4. A lot of carbon build up and no apparent signs of a leak.

I’m having a hard time getting the photos from my phone, but I’ll try to upload som from my computer later

97 SL320 · #48 02-19-2018, 04:17 PM

Did you do a leak down before you removed the head as I had outlined?

Hawk8789 · #49 02-19-2018, 06:02 PM

I never did the leak down test. I was just rear ended in my daily driver and found myself with one afternoon with my friend to pull the head. As I said, I wanted to do the head gasket anyway for the experience.

Now that I had some daylight I took a closer look at the gasket. It looks like there was no coolant leak in cylinder 4, a small leak in 1, and 2 and 3 looked like about 1/4 of the ring was letting coolant through.

ROLLGUY · #50 02-19-2018, 08:49 PM

If you really like pulling the head, just put the gasket on and bolt the head back on. If you want it to go a long time before doing the job again, have the head magnafluxed and surfaced, along with a valve grind. You should also clean the deck real good and get a precision straight edge to check the block for flatness. And don't forget to replace the valve seals. The head bolts will need replacing as well.......Rich

Hawk8789 · #51 02-20-2018, 08:57 AM

I’m way ahead of you on all that. I wanted to learn how to replace a head gasket, but I don’t want to make it a habit.

97 SL320 · #52 02-20-2018, 11:38 AM

Quote:

Originally Posted by Hawk8789

I’m way ahead of you on all that. I wanted to learn how to replace a head gasket, but I don’t want to make it a habit.

Not really.

By not doing a leak down and checking the rad for bubbles, you leave the possibility of a head crack in one cylinder and a good head gasket around that cylinder.

The head really should be pressure checked for cracks at this point.

BillGrissom · #53 02-20-2018, 04:11 PM

If the head has just a slight warp (~5 mil), a cheap trick to flatten it is to spray-glue sandpaper to a thick piece of glass and slide the head surface back and forth until flat. A guy in San Diego shows this on youtube. He does it on an aluminum head, which certainly sands faster. I don't think cast-iron heads normally warp, but check it w/ a good flat-edge regardless.

97 SL320 · #54 02-20-2018, 06:51 PM

Iron heads can develop low spots. The GM 4.3 V6 ( cut off V8 ) I did a while back developed a localized low spot in the same place on both heads.

t walgamuth · #55 02-20-2018, 07:43 PM

The iron 616 617 heads are very strong and not very likely to warp. I'd suspect a crack before warping....or 2 or 3.

ROLLGUY · #56 02-20-2018, 09:58 PM

These heads do in fact warp, and crack. I have had my shop do at least four of them, and every one needed to be surfaced. The last one had a 7 thou variance (low spot). Another had some small cracks around the prechambers. I use a piece of granite (sink hole) with a piece of wet or dry glued to it for surfacing small aluminum heads. The 5 cyl iron head would be way too heavy and hard to do this way.

Hawk8789 · #57 02-23-2018, 09:26 PM

I checked with my straightedge every which way and everything looks nice and flat. I think I’ll use the same head and save the other one. Everything cleaned up nicely and I’m hoping to put it together this weekend. It’ll be nice to drive this thing again. I bought it when I was 15 in 2002 so we’ve been through quite a lot. The previous owner was the son of a friend of my dad’s who owns a cylinder head shop back home. The whole family owned old Mercedes W123s. The son just passed away a few months ago and I’d really like to take this car home with me this spring.

Hawk8789 · #58 03-30-2018, 12:50 PM

So I erred on the side of caution and took the spare head to a shop that has a lot of experience with mercedes diesel heads. It took him 2 weeks to get to it. The head was good except for loose valve guides, so they replaced all the guides for $45. And an additional $250 to tell me the head was good. Ouch. Things keep coming up so I haven’t put it on yet.

97 SL320 · #59 03-30-2018, 07:53 PM

Quote:

Originally Posted by Hawk8789

So I erred on the side of caution and took the spare head to a shop that has a lot of experience with mercedes diesel heads. It took him 2 weeks to get to it. The head was good except for loose valve guides, so they replaced all the guides for $45. And an additional $250 to tell me the head was good. Ouch. Things keep coming up so I haven’t put it on yet.

Please post a detailed list and pricing for work the shop did.

Hawk8789 · #60 03-31-2018, 01:27 AM

I can’t find the receipt right now, but they said there were very minor heat cracks, and it had already been shaved once so he didn’t know if he could do it again, in which case, I had the other head. Aside from the valve guides it’s fine. My guess, since I bought it used, is the last guy had it leveled, but never replaced the guides and ended up parting out his car. He did say they worked on the head and valves to make sure everything was good to go, but I can’t remember the term he used. At any rate, I have the valves, springs, retainers, and stem seals installed and I hope to put it on tomorrow morning. He has his warranty and I have my other head, so I’m not worried. The guy knows his stuff. He knew exactly what it was as soon as I walked through the door and he was very helpful in person. It was my fault for telling him I worked out of state and couldn’t pick it up for a week. He just kept taking other customers ahead of me and then I had to wait a few more days on top of that to get down there.