Just for reference, peak cylinder pressure in a 603 is around 1800 psi. BMEP is around 120 PSI. That’s why you can have exhaust in the coolant without the reverse. If it was me, I’d want a test with higher pressures before using the head as is.

This statement is plain wrong. If you so inclined, show me documents that show coolant can never get into #14 head combustion chamber. The head I have now on the sdl will leak coolant into the combustion chamber and hydrolock the engine over night. This is fact and not fiction. The engine will spin a little and you hear a 'dud' noise and engine stops. I thought it was the starting motor. Put a new one in and the same. Remove injector and coolant squirting out when spinning the engine. So combustion gas and coolant can go either way. I don't understand why you insist the head is bad, it is not your time nor money. The head is going in no matter what. I am quite happy to live with this head as it was pressurized to 80psi and no leak found. I am getting out of here until the head is installed.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

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1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

English must not be your native language. Nobody ever claimed that coolant can't or won't leak through a crack. The point is that's not the only way cracks work. Of course you can have a crack that floods the cylinder, more commonly it comes from a blown head gasket though. When the head is the source, you know it's really screwed.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Has the head been checked for flatness?

Sixto
98 E320s sedan and wagon
02 C320 wagon

Cyl head flatness is for pussies.

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CENSORED due to not family friendly words

Hey ah-kay...you're old cross town sdl buddy here....I say rip for it. I know you have the 603 skills, regardless of some these poster's comments.

Re 603 w/#14's...my old sdl 603 #14 head is rolling beautifully past 449,000 miles this week & I'm sure there are a few "cracks" in that old "inferior" casting.

Heck, drive with the cap loose a notch if we're worried about blowing up the cooling system. (LOL here come the flames). About every other year I think I should be having a cracked head problem...because so many say so...been that way for a decade & a half...so I leave the cap loose for a while. No cooling difference seen at the gauge (80 to 85)...Cap has been back tight for the last year.

After reading all these posts I suppose I should loosen the cap again.

Stick to your guns and see how it works. I'll lend a hand too!

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1986 300SDL 440,xxx

No flame just science.

Put a pot of water on a stove and start heating it. You will see bubbles start to form on the bottom of the pan but not make the way to the top. This is what happens in the cylinder head when cooling system pressure is low.

In order to raise the boiling point of coolant, pressure is needed.

The cars temp gauge won't show high temps with a loose cap, but the cylinder head metal temp will be high in some spots. This leads to cavitation, steam pockets , burning of coolant ( as in exceeding the coolants temp limit ) and thermal stress in low flow areas of the cylinder head. Like between valves / exhaust ports.

Sure, you can get away with it for a while but at higher loads / temps there will be problems.

x2. Cooling system capacity is dependent on pressure to a point. More pressure is more capacity until you get to where the water pump can’t do it’s job. I drove a 603 for a while with the cap loose when there was residual pressure. It worked for just getting around. On hot days and under load I had to keep an eye on the gauge because it would climb quickly. My SDL cracks got so bad that it took a few minutes from cold start to beyond 100*C on the gauge and rock hard hoses but the radiator was cold. Same water pump and thermostat did their job after I replaced the head.

Sixto
98 E320s sedan and wagon
02 C320 wagon

Guys...Guys...Gals...

Understood...a normally pressurized system is by design going to increase boiling point and cooling capacity not to mention maintain desired coolant flow characteristics.


But I don't think ak-hay is pondering putting the 14 head into service to haul a trailer up through the alps, commute in LA traffic with soaring temps and the AC doing full duty, and so on.


Sort of kidding above... but it's an old around town car he's trying to keep in easy service without spending three or more thousand $$$ to have a drivable car for local easy street service.


Heck, several of you know I've been on the look out for a good improved casting head for years without spending more than the car is worth...to me or the market.


With regard to folks making condescending statements challenging his ability to rationalize forum feedback by questioning his "language skills", etc...News Flash...He's a very intelligent engineer by profession, speaks multiple languages, has had more 603's landing in his drive way than most folks, and knows these motors. Right next to Sixto and a few other 603 vets he's been one of my 603 go-to guys over the years.


It's a diy for a reason...and that's why he ran it up this flag pole.

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1986 300SDL 440,xxx

Please explain how a loose rad cap / low cooling system pressure will make a cylinder head last longer.

Uhhh? It's not.


Take Care

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1986 300SDL 440,xxx

I bet when he gets the car going we will never hear about how its blowing coolant out of the tank. So was the car wrecked that was in the PNP? If not, I can just about guarantee I know the reason it was sent there.

Ah-kay - go for it! I think your test is missing just one element, which is heating the head in a bath of water up to about 80 deg C. Have you looked at the FSM method? They use a block-off plate to do the same thing you did with the coins, and then immerse the head in a tank of water and heat it up to 80 deg C, keeping it pressurized the entire time.

I did a similar test, but I pressurized the exhaust passages via the exhaust manifold. I had two heads to test, neither had visible cracks. The bad head did leak at room temperature, allowing air to pass from the exhaust passage to the coolant passages. The good head did not leak even when heated up.

I made my hot bath by cutting a barrel in half length-wise, setting it up on some concrete blocks and putting a big propane burner underneath. I made a block-off plate for the end of the exhaust manifold and attached a pressure hose connector. I cut rubber seals to make a good seal of all the exhaust valves against their seats.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I had a bad #14 head (original to the car) that was just starting to mix coolant into the oil, but wasn't pressurizing the cooling system overnight. Removed the head, and it had really big cracks between all the valve seats, much worse than your junkyard head. I'll bet that just about every #14 head still in operation has cracks between the valve seats.

So you are taking a risk, given the cracks, but if you've got the time and the inclination, you may get years and years of service from that head.

However, I think you should repeat the test in a hot bath of 80 deg C.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I'll ignore the debate on crack (pun intended) and skip to the cost benefit analysis:

Since there are visible cracks, why not just have a competent machine shop weld it up, and check flatness while it's in there? Cost should be a few hundred bucks. Compare that with the cost of another head gasket kit if you have to pull the head again, along with 10-20 hours of your time, which isn't free. I know there is a shop in Sacramento that can resurrect cracked aluminum heads, there's gotta be a place in SoCal that will do the same.

And yes, a #14 head can last a long time without issues, if you don't overheat it. I understand the lack of love for the 14 but hey, if you can rebuild it for a few hundred, why not? But bolting it up obviously cracked sounds like a good way to do the same job three times in a row.

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Dave
Boise, ID
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