DIY OM603 head pressure test - head good? - Page 3 - PeachParts Mercedes-Benz Forum

ah-kay · #1 06-10-2018, 09:19 PM

Quote:

Originally Posted by Diseasel300

Stop reading into comments. Nobody's telling you to get the head professionally tested. Everyone so far is saying that THE HEAD IS JUNK. It's a known issue with the #14 casting and very well documented, including photographic evidence right here in this thread.
#14 Head Casting + Cracks = Crap. End. Of. Story.

Really, the head is toasted? That is good to know. Thanks but no thanks.

86-300sdl · #2 06-14-2018, 12:09 AM

Quote:

Originally Posted by ah-kay

Really, the head is toasted? That is good to know. Thanks but no thanks.

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!

97 SL320 · #3 06-14-2018, 08:58 AM

Quote:

Originally Posted by 86-300sdl

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.

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.

tjts1 · #4 06-11-2018, 10:40 AM

Do any of those 15L diesels they test for leaks have aluminum heads?

97 SL320 · #5 06-11-2018, 01:47 PM

Quote:

Originally Posted by tjts1

Do any of those 15L diesels they test for leaks have aluminum heads?

Probably not, but the 2001 + GM ( Isuzu ) Duramax has aluminum heads as does the Ford Power stroke 6.7 from 2011 + .

I don't have any testing procedures for these. If someone is running super high boost / load, super small crack could be unfindable with conventional methods but this would be a rarity.

jay_bob · #6 06-11-2018, 12:41 PM

I'm watching this too to see how it ends up.

Would be very a interesting data point in the OM603 experience, if a visibly cracked #14 head, holds 50 psi in an ambient temperature water bath, and ends up being serviceable.

Good luck and be sure to let us know how it worked out. Lots of people condemning #14s for small cracks like in your photos, so if your test works out well long term that could be a very good thing.

barry12345 · #7 06-11-2018, 01:35 PM

Cars are disgarded for reasons. This could be why that one in the wreckers was.. If you are going to persist. Go back to the car to see if there is anyway to contact the last owner. Some people leave papers in cars they send in and perhaps even licence plates in certain states.

Personally I suspect the cracks in these heads act like one way valves. Under high combustion pressures they admit pressure to the coolant passages. Under low pressure they no longer leak.

This is kind of verified by 603 engines with cracked heats still have coolant system pressure the next morning as a test. Logically to me if they also leaked at low pressure. There would be no retained pressure in the coolant system the next day. The pressure input could be very high also but any accumulating above the radiator cap limit. Would just be relieved by it.

I am not suggesting what you should do. Yet if I lived in your part of the country myself I would look for a newer head. Primarily because the odds of finding one are very high there compared to my region. Those cracks may also be a good reason for an engine to run hot.

Also other members could comment. We have quite a few members that have changed cracked 603 heads. Was there coolant in those cylinders that had the cylinders with the cracks in their heads? If my thoughts are right in many perhaps none was observed.

Since of course I only have limited abilities and experience. I am almost positive that you can find a rebuilder of Mercedes heads in your general area. The most famous one is even in your state I believe.

My suspicion is they will tell you that any cracks found of your type existing in that number fourteen head. They probably do not even bother testing it. Simply because it is what it is. A number fourteen head that has cracks. In addition all cracks of that type you have always create issues they found.

There are heads with real obvious cracks like the early Volkswagon water cooled diesel engines. The first one I pulled scared me . Until I found out they were normal unless really wide. Every cylinder had them as well. Yet they never caused me a problem. We pulled a lot of those heads to change failing head gaskets.

Plus if by some odd chance my thoughts are correct. They may have found out they do not leak test in the conventional way a long time ago. Again just a suspicion of mine. Unless the cracks really open up. The hot water expands the alloy head of course. It is just not restrained when it cools down like it would be to some extent when mounted on the block.

Also remember that an alloy head on a cast iron block has movement in relation to the cast iron block. So in service this can actually manipulate the cracks slightly. Yes it slides on the head gasket but the forces are still substantial on the casting. Over the years I have thought there are perhaps many contributors to the high failure rate of these heads anyways. Just food for thought.

ah-kay · #8 06-11-2018, 04:02 PM

Quote:

Originally Posted by barry12345

Cars are disgarded for reasons. This could be why that one in the wreckers was.. If you are going to persist. Go back to the car to see if there is anyway to contact the last owner. Some people leave papers in cars they send in and perhaps even licence plates in certain states.

Personally I suspect the cracks in these heads act like one way valves. Under high combustion pressures they admit pressure to the coolant passages. Under low pressure they no longer leak.

This is kind of verified by 603 engines with cracked heats still have coolant system pressure the next morning as a test. Logically to me if they also leaked at low pressure. There would be no retained pressure in the coolant system the next day. The pressure input could be very high also but any accumulating above the radiator cap limit. Would just be relieved by it.

I am not suggesting what you should do. Yet if I lived in your part of the country myself I would look for a newer head. Primarily because the odds of finding one are very high there compared to my region. Those cracks may also be a good reason for an engine to run hot.

Also other members could comment. We have quite a few members that have changed cracked 603 heads. Was there coolant in those cylinders that had the cylinders with the cracks in their heads? If my thoughts are right in many perhaps none was observed.

Since of course I only have limited abilities and experience. I am almost positive that you can find a rebuilder of Mercedes heads in your general area. The most famous one is even in your state I believe.

My suspicion is they will tell you that any cracks found of your type existing in that number fourteen head. They probably do not even bother testing it. Simply because it is what it is. A number fourteen head that has cracks. In addition all cracks of that type you have always create issues they found.

There are heads with real obvious cracks like the early Volkswagon water cooled diesel engines. The first one I pulled scared me . Until I found out they were normal unless really wide. Every cylinder had them as well. Yet they never caused me a problem. We pulled a lot of those heads to change failing head gaskets.

Plus if by some odd chance my thoughts are correct. They may have found out they do not leak test in the conventional way a long time ago. Again just a suspicion of mine. Unless the cracks really open up. The hot water expands the alloy head of course. It is just not restrained when it cools down like it would be to some extent when mounted on the block.

Also remember that an alloy head on a cast iron block has movement in relation to the cast iron block. So in service this can actually manipulate the cracks slightly. Yes it slides on the head gasket but the forces are still substantial on the casting. Over the years I have thought there are perhaps many contributors to the high failure rate of these heads anyways. Just food for thought.

One way valve out of a block of aluminum? Wow, that is news to me. Air will find a way to escape, in cast iron or aluminum. So I would discount the head material. If you can't find a leak at 50psi then I don't know what will. I ramped it to 80psi and no bubbles. My existing head is so bad that coolant will leak into the combustion chamber and hydrolock the engine. I will repeat the same test if I have time when I swap it out with this jy head.

Diseasel300 · #9 06-11-2018, 04:38 PM

Quote:

Originally Posted by ah-kay

I did not remove it from the junk car, someone removed and abandoned it after seeing the cracks. It's either he was missing out or my lucky day. We will see.

We will indeed. I wouldn't have pulled a 14 head unless I was desperate and didn't have time to find a 17 or later.

Quote:

Originally Posted by 97 SL320

Probably not, but the 2001 + GM ( Isuzu ) Duramax has aluminum heads as does the Ford Power stroke 6.7 from 2011 + .

A lot of time elapsed between 1986 and 2001. Any manufacturer with a brain would have learned from Mercedes' weakness with the original #14 casting. Cracks on later castings or on other manufacturers' designs aren't as critical as they are with the #14 603 head.

Quote:

Originally Posted by ah-kay

One way valve out of a block of aluminum? Wow, that is news to me. Air will find a way to escape, in cast iron or aluminum. So I would discount the head material. If you can't find a leak at 50psi then I don't know what will. I ramped it to 80psi and no bubbles. My existing head is so bad that coolant will leak into the combustion chamber and hydrolock the engine. I will repeat the same test if I have time when I swap it out with this jy head.

Most of the 14 head failures don't leak coolant. They leak combustion gas into the coolant jacket and pressurize it causing overheating. The typical telltale sign is cracks between the valve seats when the head is pulled. One is bad enough, having 3 of the 6 cracked suggests that engine had a rough life or the casting in question is particularly weak.

ah-kay · #10 06-11-2018, 04:52 PM

Quote:

Originally Posted by Diseasel300

Most of the 14 head failures don't leak coolant. They leak combustion gas into the coolant jacket and pressurize it causing overheating. The typical telltale sign is cracks between the valve seats when the head is pulled. One is bad enough, having 3 of the 6 cracked suggests that engine had a rough life or the casting in question is particularly weak.

When a head is cracked, it means breached passage. Water will go to chamber, gas wiil go to coolant. It is just a matter of how much. I think we agree to disagree. Just leave it at that.

tjts1 · #11 06-11-2018, 05:21 PM

Is this really worth arguing over? Let him install the head and let's see what happens. It'll be an interesting experiment no matter what the results. I hope the OP takes some closeup pics of the cracks before installing it.

Hit Man X · #12 06-11-2018, 05:47 PM

It's the pleats.

Diseasel300 · #13 06-11-2018, 06:17 PM

That's cute comparing a blown head gasket to a cracked head. Nice try, but no. The M104 also has nowhere near the cylinder pressures of the turbo 603, nor does it have a weak casting design like the #14 head. Sometimes it pays to be familiar with the specific issue at hand rather than using generic wisdom. In any other case on any other engine or cylinder head I'd be in agreement, but not this time.

Mxfrank · #14 06-11-2018, 06:44 PM

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.

sixto · #15 06-11-2018, 09:39 PM

Has the head been checked for flatness?

Sixto
98 E320s sedan and wagon
02 C320 wagon