DIY OM603 head pressure test - head good? - Page 2 - PeachParts Mercedes-Benz Forum

sixto · #16 06-10-2018, 12:55 PM

Someone mentioned testing the head at operating temperature, I’ll throw in torquing to spec. A head torqued in place might cause cracks to expand.

Sixto
98 E320s sedan and wagon
02 C320 wagon

tjts1 · #17 06-10-2018, 01:30 PM

If there's any question whether or not a 14 head is cracked, instead of pressure testing it I would clean it thoroughly and check it with fluorescent dye. If a crack hasn't reached the coolant system yet it will soon.

Despite looking externally similar, #17 and up heads are very different inside. Open up the large coolant plugs on the intake side of the head and look inside. The deck is much beefier on the later heads. As far as I know, the om603 was the first aluminum head turbo diesel on the market from any manufacturer. Mercedes made some mistakes on this design which they later corrected.

ah-kay · #18 06-10-2018, 03:33 PM

Quote:

Originally Posted by tjts1

If there's any question whether or not a 14 head is cracked, instead of pressure testing it I would clean it thoroughly and check it with fluorescent dye. If a crack hasn't reached the coolant system yet it will soon.

Despite looking externally similar, #17 and up heads are very different inside. Open up the large coolant plugs on the intake side of the head and look inside. The deck is much beefier on the later heads. As far as I know, the om603 was the first aluminum head turbo diesel on the market from any manufacturer. Mercedes made some mistakes on this design which they later corrected.

Shall I take it to a professional and ask them to check with flourescent dye? They probably will laugh their heads off. They all pressure test it with air. What I have is a #14. It is not what I wish to have, it is a matter of doing the best with what I have. Any crack will show up with air, air will pass thru cracks, i.e. bubbles, no matter how small. I honestly don't think temperature or torque would affect the test redult one way or the other. The professional don't torque it.

Diseasel300 · #19 06-10-2018, 03:41 PM

Your pressure test used a very low pressure pushing outwards from the coolant channels.

When in operation, the head is extremely hot, the pressure in the cylinder is >1000PSI, and the head bolts have it clamped in position. All these things add up to make leaking from the cylinder into the cooling system far more likely than the other way around.

Sometimes it pays heed to listen to what other people are telling you from experience. Again, it's your car, your time, your money, your effort. You do what you want.

ah-kay · #20 06-10-2018, 03:54 PM

Quote:

Originally Posted by Diseasel300

Your pressure test used a very low pressure pushing outwards from the coolant channels.

When in operation, the head is extremely hot, the pressure in the cylinder is >1000PSI, and the head bolts have it clamped in position. All these things add up to make leaking from the cylinder into the cooling system far more likely than the other way around.

Sometimes it pays heed to listen to what other people are telling you from experience. Again, it's your car, your time, your money, your effort. You do what you want.

With due respect please send me a link to see how the PROFESSIONAL check the head. I want to see whether they heat it, torque it, dye it, combust it to 1000psi and i am willing to part with my hard earned money.

Diseasel300 · #21 06-10-2018, 04:45 PM

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.

tjts1 · #22 06-10-2018, 05:23 PM

Quote:

Originally Posted by ah-kay

Shall I take it to a professional and ask them to check with flourescent dye? They probably will laugh their heads off. They all pressure test it with air. What I have is a #14. It is not what I wish to have, it is a matter of doing the best with what I have. Any crack will show up with air, air will pass thru cracks, i.e. bubbles, no matter how small. I honestly don't think temperature or torque would affect the test redult one way or the other. The professional don't torque it.

There are florescent dye kits that are cheaper/ easier than a pressure test. In my opinion any crack whether you can force air through it or not means the head is toast.

I think where we differ in the opinion that air pressure will find any leaks. I don't think that's a reliable test in this situation for reasons that others have already discussed.

Good luck with the project.

ah-kay · #23 06-10-2018, 09:15 PM

Quote:

Originally Posted by tjts1

There are florescent dye kits that are cheaper/ easier than a pressure test. In my opinion any crack whether you can force air through it or not means the head is toast.

I think where we differ in the opinion that air pressure will find any leaks. I don't think that's a reliable test in this situation for reasons that others have already discussed.

Good luck with the project.

I think you diverge with a lot of professionals. They all use fittings to pressurizing the coolant chamber and submerge the head in water. I am diy-ing a method to test a head and all I get is that the head is toasted. Thanks but no thanks.

ah-kay · #24 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.

ROLLGUY · #25 06-10-2018, 09:21 PM

Quote:

Originally Posted by tjts1

As far as I know, the om603 was the first aluminum head turbo diesel on the market from any manufacturer. Mercedes made some mistakes on this design which they later corrected.

The early (1984?) 190D had an aluminum head (basically the same engine minus two cylinders). Also, the Mitsubishi 4D55 in 1983 had an aluminum head. Other countries might have gotten these engines in earlier year models as well.

tjts1 · #26 06-10-2018, 09:36 PM

Quote:

Originally Posted by ROLLGUY

The early (1984?) 190D had an aluminum head (basically the same engine minus two cylinders). Also, the Mitsubishi 4D55 in 1983 had an aluminum head. Other countries might have gotten these engines in earlier year models as well.

But were these TURBO diesels?

MB redesigned it's turbo diesel heads in 89 and by 93 was using the turbo head castings in it's NA engines as well. As far I know the early om601 and om602 NA engines didn't suffer the same failure.

Diseasel300 · #27 06-10-2018, 09:50 PM

Quote:

Originally Posted by ah-kay

I think you diverge with a lot of professionals. They all use fittings to pressurizing the coolant chamber and submerge the head in water. I am diy-ing a method to test a head and all I get is that the head is toasted. Thanks but no thanks.

And if you took that head into a machine shop and they saw the cracks in the head, it would never even make it to the tank to be pressure tested. Cast iron heads are one thing, aluminum is another animal.

Just because you don't like what someone tells you doesn't mean you're right and they're wrong.

Prove you're right. Put the head on your car and test it out. Keep notes on coolant consumption, engine heat level, and pressure in the coolant system. Keep tabs on how long it lasts and how much money it cost you to buy the head, futz around with it, and install it (including hardware, head gasket, coolant, etc.).

If it works out and holds up, I'll HAPPILY admit I was wrong. If it doesn't, be prepared for "I told you so".

ah-kay · #28 06-10-2018, 09:57 PM

Quote:

Originally Posted by Diseasel300

And if you took that head into a machine shop and they saw the cracks in the head, it would never even make it to the tank to be pressure tested. Cast iron heads are one thing, aluminum is another animal.

Just because you don't like what someone tells you doesn't mean you're right and they're wrong.

They don't want to take my money?

You are not here. I pressurized it to 80psi and still no bubbles. Shop only pressurize it to around 20psi. So I am very confident that the head is good. It is going to be installed in a sdl. So stay tuned.

97 SL320 · #29 06-11-2018, 10:14 AM

Quote:

Originally Posted by Diseasel300

Cracks between valves = junk. It isn't a question of will it leak, it's how badly does it leak?

Not always. I'd have to dig around for some manuals but cracks between the valves are common and there is an acceptable limit. In general, cracks here are only acceptable if they don't reach the valve seats and are under a certain length.

Quote:

Originally Posted by Diseasel300

The pressure in the cylinder is much higher than the 350-400PSI of compression when the fuel ignites.

Cylinder pressures are high only for a very short time. Map out a cylinder pressure curve and you will see.

Using 50- 90 PSI to check for combustion to coolant leaks is a very valid test that is used my actual automotive machine shops.

funola · #30 06-11-2018, 10:20 AM

Quote:

Originally Posted by 97 SL320

Not always. I'd have to dig around for some manuals but cracks between the valves are common and there is an acceptable limit. In general, cracks here are only acceptable if they don't reach the valve seats and are under a certain length.
........................

If the cracks between valves are within limits, there are outfits that can machine away the cracks, weld in fresh aluminum, more machining, then do a valve job.

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