300SDL - Head gasket is shot ?? - PeachParts Mercedes-Benz Forum

ah-kay · #1 10-19-2011, 02:55 PM

Need some infinite wisdom from the forum. I just installed a new starter and now I think the head gasket is shot. Car has 341K miles with #14 head. Never overheated since I bought it at 316K. So it has done almost 25K in 2 years.

1) More smoke than it used to be, at cold or hot.
2) I remove the expansion tank cap when the engine is cold. Start the engine and I can see the coolant rising immediately and overflow. Combustion/exhaust gas entering the cooling system??
3) It is losing cooling real quick. It did not happen before.
4) btw: car does not overheat.

What option I have? Replace the gasket? If I do, what make/brand of gasket? Any good thread here on head gasket R&R?

Thanks

benhogan · #2 10-19-2011, 03:41 PM

do you have soupy or milky oil?

ah-kay · #3 10-19-2011, 04:18 PM

Quote:

Originally Posted by benhogan

do you have soupy or milky oil?

Oil is normal, sooty color, not milky. No oil sheen in coolant either.

barry123400 · #4 10-19-2011, 04:21 PM

Do the cold next morning test. Although since the head has to be removed it does not matter much. May be gasket or crack in head. Unless the gasket failure is obvious have the head checked for cracks.

I am not really sure you have to overheat these engines to crack a head. Just the normal thermal cycling over the years may be enough. The good thing in your case is usually with a crack in the head you do get overheating.Not cold coolant blowing out.

BoiseBenz · #5 10-19-2011, 05:03 PM

Quote:

Originally Posted by ah-kay

2) I remove the expansion tank cap when the engine is cold. Start the engine and I can see the coolant rising immediately and overflow.

That's HG for sure; a crack should not flow that much combustion pressure.

It's not a "hard" job; the only special tool I recall is the standard kraut "triple-square" head bolt tool.

sixto · #6 10-19-2011, 07:48 PM

Whatever head gasket they sell through FastLane, the Buy Parts link at the top of the page, is good. Get a head gasket set which includes manifold gaskets, valve cover gasket, upper radiator hose housing gasket, injector seals, heater hose o-ring, head plug crush washers, etc. If you're thinking of upgrading to an afterglow relay and want to keep the BFS temp switch, install an afterglow relay temp sensor in the head while the intake manifold is off.

I wouldn't replace the chain while the head is off. It's not really easier and you don't need another variable if the engine doesn't run properly with the new head gasket.

Not a lot of while-you're-in-theres with this engine. Anytime the intake manifold is off is a good time to evaluate injector line clamps. You have better access to the IP but not for a full reseal. The return line from the IP will be easy to replace if you feel the need.

Check the condition of the upper chain guide and tensioner guide. The upper guide has to come off the pull the head. The front cover has to come off to replace the tensioner guide.

If you're inclined, put a dial gauge on the #1 piston and confirm that the TDC indicator tab is adjusted correctly.

Sixto
87 300D

LoosBenz · #7 10-19-2011, 09:03 PM

Unless they are brand-new, no more than they cost, I'd replace the glow plugs while doing this job.

ah-kay · #8 10-21-2011, 01:06 AM

Car would not start tonight. Remove the injectors and hand cranked it and water sprouting out. What a mess! I have not done a HG R&R on diesel engine, so any advice is welcome.

Do I need special tools? Any DIY thread here? I have the FSM on the engine. Any other manuals I needed?

Thanks

sixto · #9 10-21-2011, 02:41 AM

Too complicated to rewrite in a post. You need a copy of the factory service manual (FSM). Mind that some versions of the 126 FSM have the description and arrows for loosening the cam towers mixed up. Double check with the forum when you get to that point. The only required tool you might not have is a triple square for the head bolts. Some head bolts are outside the valve cover among the injectors so you can get the right size. A timing chain guide rail extractor is worth the cost but you can get by with a high strength bolt and a bunch of washers (5mm or 6mm?).

Sixto
87 300D

barry123400 · #10 10-21-2011, 12:30 PM

Real care in the sequence of removing the cam towers is suggested on this engine.

amosfella · #11 10-21-2011, 09:17 PM

You're looking for snap on part number STSN10E or FTSM10LE. That's your wrench to remove the head bolts. XZN or tripple square. I'd buy the snap on one for the simple reason that the alloy they use is a lot harder and tougher, and that it's better machined... A few guys have learned that the hard way.
I believe the guide rail pins are a 5mm thread. Get a few short lengths of 3/8 inch black gas pipe, and about a dozen washers for the bolt...
I'd replace the chain guides and tensioners while your in there... I have only done a head gasket replacement with the engine outside the car... I took the whole front cover off the engine to set it and I did the chain while I had it apart... The engine was fogged and set in storage... Still there.... It has never been run, so I dont' know how my job turned out...

ah-kay · #12 01-09-2012, 01:26 PM

The HG is shot for sure but I fixed it with 'snake oil'. I used the 'Blue Devil' HG sealant and I cannot be more pleased with the result. I have done about 2K miles since the treatment and the car runs great.

1) No more hydrolocking the engine
2) No more losing of coolant - used to be a quart or more a day
3) No more hard top radiator hose in cold morning
4) No smoking

The jury is still out with 2K but it is better than a 30 hours HG R&R job. I reckon that I may butcher up the engine if I do the HG myself.

Disclaimer: One word of caution. The result may vary with your engine but I am a happy camper for the $30 sealant. It is worth a try for little money, nothing to lose and everything to gain. If all failed then take the HG route.

barry123400 · #13 01-09-2012, 04:36 PM

Can you read the container and see if they mention what the components of the sealer are if listed?

ah-kay · #14 01-09-2012, 05:01 PM

All HG sealant work on Silicon Sulphate or 'Water Glass'. Silicon Sulphate will turn into GLASS when subject to high temperature, i.e. when combustion gas enters the coolant. This is the theory and so far it works in practice. It could be a permanent fix or could be a temporary fix but the write up on Blue Devil is very good. I know a lot of shade tree car salesmen use it to mask HG problem. It may work or may not work depends on where the HG failure is. It is worth a try in my opinion for so little money. You need to follow the instructions to the letters and drain ALL anti-freeze from the coolant system first.

barry123400 · #15 01-09-2012, 09:38 PM

I did not realise they were using water glass for sealing head gaskets as well. Thats why I asked if the ingedients were on the label.

Your friendly local druggist can order in water glass as well. Or at least in the past. Usually was the cheapest way to get it. Times change though.

In the presence of combustion it fuses into a glass like substance. I assume it also fuses eventually at lower temperatures.

I saw the water jackets coated by the stuff on some engines I knocked down. Who knows how much they put in though? from time to time post that it is still lasting or has failed.

Some applications seemed to last for the length of ownership of the car. I wonder if it caught a crack in the head instead of a failed head gasket in your case?

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