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Old 05-22-2002, 06:09 PM
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Join Date: Sep 2001
Location: Concord, MA
Posts: 603

Finally completed head gasket/valve is the quick version of the blow-by-blow...

November...put in new thermostat (Febi), car runs hot (95-100 c). Put in another thermostat (Behr), car still runs hot!!..check coolant...little bit of engine oil; check head space in coolant reservoir...carbon monoxide present. Diagnosis-bad head gasket. has 268,000 miles. If I remove head for head gasket, I will do valve job/guides. Instead of doing valve job on my head, I decide to get rebuilt head from Cylinder Heads International (Texas) for $350.. (This to avoid down time on my main ride.)

March ...all set to do the head "switcheroo"...I pull the pre-chambers out of my car (head still in place) to check for damage. They look good....I just happened to try how the pre-chambers fit in the rebuilt head sitting on the kitchen table...THEY WONT GO IN!! Tip of pre-chamber = 16mm diam, hole in head = 14mm diam!! As it turns out, the head I recieved was from a non-turbo 300D...has different pre-chambers.

I call CHI and they say they have the proper head with bigger pre-chamber holes, from turbo....they will machine and send out that day!!!

April...I recieve second head...valves are terrible (wrong machine angle (45 deg instead of 30), valve edges sharp, chewed up. Also, mating surface (machined) very rough...fingernail-catching grooves. I take valves from first head (which look good) put in second head, lap them in. I take a chance, assume the mating surface is ok (even though that little voice inside said otherwise)..and I installed the second head.

Result: car runs ok, but still runs hot (95-100), with major residual pressure in coolant reservoir in the morning...conclusion - rough machined surface of head not sealing properly with head gasket.

Note I still have two extra heads on hand ...the first incorrect one, and the original from my car.

I now decide to get a valve job done locally on my original head, then return both rebuilt heads to CHI for a refund.

Valve job done at reputable shop with lots of experience on Mercedes, including is cost breakdown:

Dissassemble and hot tank head .....$60
magnaflux head................................$40
Grind valve seats..............................$175
Remove and replace 10 guides (labor $10 ea.)........$100
Ten guides (parts, $6.80 ea.)...........$68
Size 10 guides ($4 ea)...............$40
Resurface cylinder head...........$60
New valves -
5 exhaust valves @ $37.80 ea........$189
5 intake valves @ $29.40 ea............$147




Early May - Take off bad head, put on good head (note...all work done in my driveway, hoping for good weather, no enthusiasm to repeat what I just did a few weeks earlier.)

Result.......Great! No residual pressure, no oil in coolant, no carbon monoxide in coolant reservoir, car runs great. still runs hot...95-100 with a few peaks to 110!!!!!!!

A few days ago...I took out the Behr thermostat, put in an Auto Zone Wahler.....PERFECTO!!!!!!! Car runs at steady 85 deg C.

Finally, life is good, car runs great, no residual pressure, good coolant temps. etc......finally out of the doldrums, still hurting in the wallet.

(As part of this process, I also replaced all coolant hoses, oil cooler hoses, gasket on oil filter housing, and a few other things)

Now to tackle body work ...rusty doors on passenger side.

What an ordeal!!!!!!!!

Mark M

1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)
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Old 05-22-2002, 11:37 PM
jcd jcd is offline
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Join Date: Jun 2001
Location: Northern New Jersey
Posts: 1,102
Congrats Mark

You get the stick to it award.

You're my role model.

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Old 05-23-2002, 04:24 AM
The Warden's Avatar
Certified diesel nut
Join Date: Mar 2002
Location: Pacifica (SF Bay Area), CA
Posts: 2,946
I second jcd's comments.

I'm impressed that you followed through with the whole thing. I probably would have given up, after going through most of that...
2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999
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Old 05-23-2002, 11:21 PM
ck42's Avatar
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Join Date: Nov 2001
Location: Holly Springs, GA
Posts: 866
This Thermostat issue seems like a good candidate for the even has ME wondering about mine. Mine runs right in between the 80 and 100C marks which puts it at 90C. I keep hearing about others' running at 85C.

But! you really tackled this problem in a major way! I was hoping for something more spectacular after all the work you did! Kind of a let down with it just being the stoopid thermostat. One thing's for sure tho now, that puppy is gonna run great!!!
1985 300SD - 'Grace' (198K mi.)
2010 Honda Fit Sport
2013 Honda Accord Sport
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)
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Old 05-24-2002, 05:44 AM
Posts: n/a
My hats off to you!!! Sticking with it is the key to success. I think it is also many new thermostats can you possibly put in that are bad??? Amazing!
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Old 05-24-2002, 01:17 PM
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Join Date: Sep 2001
Location: Concord, MA
Posts: 603
To be sure....

I DID need a new head gasket (oil leaking into coolant), and a valve job was in order (existing valves were pretty chewed up and guides were gone). So I would have done the work anyway. But the overheating sure made me scratch my head (my own head) a few times, especially after valve job/head gasket replacement!!!!

Its amazing the overheating was ONLY due to the German thermostats!!!! I cant believe the Auto Zone Wahler does the trick, and the Febi and Behr are NG!!

I heard the same thing from a few previous posts here, and I didnt believe it, thinking that there was some other factor.

I'm now a true believer!!!
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)
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Old 05-26-2002, 02:31 AM
Posts: n/a
That machine shop sure Stuck it to you!!! Compare that to a set of Bowtie Aluminum Heads complete valve job for around $200~ And that is from a Speed Shop! Which includes surface grind to clean head mating surfaces.

Obviously you didn't check around. Doesn't matter if it is a Mercedes head or a set of Chevy Bowtie Alumimum Heads. Must be nice to have money to donate to machine shops that want to charge high dollar.

And on top of all that, you never got a double angle grind on the valves/seats - higher performance and better performance for higher compression engines! 13.5:1 and higher

And why would you replace the valves? Were they burnt so bad they couldn't be ground? That was a pure waste of money!

As for thermostat - a flat washer with a 3/8" hole will keep an engine cool for circle track racing which is a lot more strain than you'll put on your car. If it still is too warm, drill out to 1/2" hole.
Is your fan in the right place? If the fan blades are too far back into the shroud it won't cool very well and same is true if towards the engine too far. For maximum effectiveness, the center of the top of the fan blades should be at the edge of the shroud. (half of blade hidden by the shroud)

Are the fins of the raditator clogged with bugs/dirt? or bent?

AutoZone is a very cheap place to buy a lot of your Mercedes needs!
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Old 05-26-2002, 04:01 AM
Holson Adi's Avatar
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Join Date: Jul 2001
Location: Boston, MA
Posts: 2,561

could you check your mail?

I just wanna know which shop you took the car to.

2008 BMW 335i Coupe
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Old 05-27-2002, 06:57 AM
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Join Date: Apr 2002
Posts: 3,473

Can you can really get bowtie heads done with parts for $200? How come you think that the price paid for the machine work is a lot? Tanking and cleaning seems reasonable, the other stuff seems reasonable. Do you have any bowtie heads for a 327 vette engine 65?

Congradulations on doing your cylinder head. That seems like a lot of work. Its good that your wife let you use the kitchen table. My mom hates that, that is why she "made" my dad build a shop. haha.

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Old 05-27-2002, 08:12 AM
Posts: n/a

You are now the honorar "Man".

I salute the fact that you ended up with a functioning motor and refunds on the bad heads. It would have been easy to end up with a boat anchor that looks like a 617 head and a bu s pass for getting to work.
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Old 05-27-2002, 09:41 AM
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Location: charlotte hall md.
Posts: 248
Mark your an inspiration.
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Old 05-28-2002, 12:29 AM
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Sorry, no more Bowtie heads, had 3 sets. Sold two pair and swapped other set for some other goodies.
I guess it is all about "who" you know. Machine shops that you scratch their back and they do likewise.
Normally boring to most guys is $120 per hole, me $50 a hole. Head Shaving? $20 bucks. Surface grind to clean up? sometimes free. Tanks soaks are about $25 dollars depending on whether he is busy or not.
But then most people on here don't go to Auto Swap meets, or weld or do much of their own mechanical work. Most don't work at the local race track. And most probably don't work on race cars. So they don't know what is a Rip-Off and what is a good deal! Most probably don't plasti-gauge their own engines.
And more than likely don't have your Mercedes Ported and Polished or line-bored!
I don't suppose while you had that head off that you ported and polished the intake and exhaust ports, did you? Both on the intake ports of the intake manifold and the head. And then polised both mating surfaces.
Did you at least replace the Valve springs? That would have been more important than replacing all 10 valves!
You could have done that yourself.
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Old 05-28-2002, 01:25 AM
HGV HGV is offline
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Location: San Francisco
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Do you really think that polishing ports will make a difference? For that matter why not CC the heads as well. I have done all that on engines that I expected performance from, but not a diesel. You should give credit where credit is do. Most of us on this forum own diesels not for their speed but all the other attributes. The fastest 240D would be left in the dust by my old and never missed slant six dodge dart.
63 190d (sold)
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Old 05-28-2002, 01:59 AM
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And a Lotus with only a 1600 cc engine would leave that Slant six - so what is the point?

My original point was, I saw someone who I felt had gotten ripped off and ripped themselves off.

Maybe if more people lived on a very limited fixed income they'd be more inclined to shop around to get the better pricing.

As to porting, grinding out the ports, and polishing them, what does this function do? What is the end result?

Most engines built in today's high mass production society are anything but well machined engines, where every part is polished and built with Care!
It is surprising that a Tecumseh small engine has many polished parts. Actually, I was a bit surprised! Honda does this also.

But, what does it actually do? For one, it allows the engine to breathe much more easily.

Remember, we are not talking about a 850hp engine or a 5000hp engine.
But rather an engine that is if anything very much underpowered!
So, every small amount makes a large difference.

A good example is at the drag strip. A very small change can make the difference between winning and taking 2nd place. Something as small as the way a nut looks like inside the engine.

Every thing done isn't always for Speed! sometimes it is for more effeciency.
Why do automakers place onboard computers in cars? They're not a racing vehicle, so why the computers?
Why buy a tire for your car that rolls easier? Is that for speed or for fuel mileage?
Why do guys put on K&N air filters on their Mercedes? Why do Mercedes Benz catalogs advertise K&N filters? Do they think we are all out for speed and high performance?
Don't suppose that this small thing could make the car actually perform better, could it?
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Old 05-28-2002, 04:07 AM
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Join Date: Apr 2002
Posts: 3,473
to benz240D

Benz240D, I appreciate you checking into the bowtie heads for me. Thanks. Seeing that you live in michigan, I would assume that anything regarding machine work would be much cheaper than other places because so many cars are produced around that area. Since our economy has slowed, many in the area may do any work for cheaper just to have it.

or maybe

The machinists in michigan are more efficient that machinists in other parts, therefore what you think is a deal in your area may be drastically more expensive somewhere else in a different economy. The economy in michigan probably concentrates around cars. The economy in the bay area, for instance, may focus on computers, therefore machinists are of less demand, so they have to charge more to get the same amount of income because they do less business.

I would have to agree with you that any little mod to a diesel would help. You give the example at the drags, so I will expand on that. Well alot of my friends drive honda. They say man, my headers and cat back exhaust really help. I think yeah with a v8 that's 15 horsepower, and no room for my hands, and that would yeild maybe 5%, so what, but to them 15 horsepower over 100 hp is a lot. So with a 240D with probably somewhere around 80 hp (not too sure on this figure), giving it headers would probably give 5 hp, and porting and polishing the heads probably another 5, thats a lot of extra power to a little diesel, and if someone made a turbo kit for a 240D, it would be a pretty quick car. The problem is, its hard to find bolt on items for the diesels besides K&Ns. I put one on my diesel, I didnt really see much of an improvement, but the keep more debris out of the engine.

Would you agree?


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