5011 - Bad Compression? Rings or Head Gasket

[5011-Fan]

I will try to make this simple:

- Ran it hard and overheated until radiator was empty. (temp gauge read 100 which was BS) Cooled down with water hose inside and outside of engine. All the water went directly into the crankcase mixing water with oil. Oil surfaced in the radiotor.
- After cooling down: drained/replaced oil, replaced AIR in radiator with WATER, torqued head bolts back to 140 ft.lbs.

PROBLEM: Put-puts during cranking instead of clean steady turns until she gradually starts like normal. Does not start and I get black smoke out of the stack.

QUESTION: Is this due to lost compression ? Do I have to replace the head gasket AND the heads now? Is there a possibility that I will have other things to replace (cylinder rings). How can I test the compression of the cylinders? BTW...is it me or does a 3 CYL Zetor Engine (5011) NOT HAVE glow plugs??? Is this a compression only spark????

HELP before I order the parts...THANKS!!! Love this tractor and it is worth the effort.

5011-Fan

 

[Renze]

hmm... The dumbest thing you can do is pour water over a hot engine.

The engine, hot, is a few millimeters bigger than a cold engine. Because of cylinder head temperatures of over 600. When you pour cold water, the surface that is exposed to the water will shrink, and the deeper metal cannot follow. That causes extreme stresses in the material, so i bet for a crate of beer, that your cylinder heads are bent. :-x
With a bit of luck, your crankcase hasnt cracked.

Anyways, new head gasket, grinding the heads on a surface mill, new valves and new gaskets will get you going again... 50 euro for flattening, 300 euro for parts... Are you going to do the job yourself ? if not, calculate a day of work too.

 

[markku]

We did accidently run one 7701 Zetor engine so hot it stucked! (Yes, we are stupid I know. This should not happen it all points are checked as we did, but the new original v-belt we changed was faulty....)

I let it get cooled very slowly and changed a new v-belt (not original barum v-belt at this time). Then I did run engine with starter about 20 sec and started the engine. I changed oils 3 times after each 50 hours.

At this day tractor has new happy owner and i think nobody hasnt opened the engine. There is little bit over 2500 hours after accident......

 

[twinpartners]

Renze...there is a famed old myth that you should not pour cold water on a hot engine. This comes from people taking a hot glass out of the dish washer and putting cold water in it. This would cause the glass to break. (common sense..glass is thin)

Fact is that engines are cast with hot molten iron and dunked in a pool of cold water in order for them to keep their form. When pouring water from a garden hose onto a 600 degree hot engine...it immediatly boils at about .002 before the surface and evaporates into steam. The water never has the opportunity to reach the surface of the block/head. This is like trying to spit into the sun. The only way that you could crack a block (or heads) were to dunk them in ice cold water without them being in a cast at 600 degrees. The little stream of water coming out of the garden hose does not have the physical capabilities of cracking anything. As a matter of fact, it is used to prevent the engine from siezing by not allowing the rings (which are very thin pieces of metal) from molting into the cylinder walls and the pistons, which after normal cooling would no longer allow the engine to crank because the pistons are now forged to the cylinder walls via the melted rings. At the same time it allows for minimal contraction of the cylinders so that they do not expand to the point of molting into the side of the block. This is much more difficult with engines with cylinder "sleeves". This is best done when the engine is 600 degrees and the head gasket is already blown, allowing water to seep into the cylinder chamber. If I had not used the garden hose method, I would have completely siezed this engine because the temperature was well above the 600 degrees. The reason I know this is because my exhaust pipe/muffler melted completely off of the u-joint at the exhaust manifold.

Common sense would in this case mislead you to believe that pouring small amounts of water would cause a whole thickly cast engine block to crack or a head to warp because of the hot glass with cold water as mentioned above. In my years of building engines and watching them being made...I have not seen a small garden hose ever crack a block or warp a head. Heads are warped because of the excessive heat and not the sudden contraction due to a garden hose (which is physically impossible). The heads expand past their casted dimensions and do not resume back to their orginal form during contraction (either fast or slow...doesn't matter). That is why heads will warp differently depending on the elevation and outside temperature during contraction.

My question to the engine experts: due to the excessive heat (as mentioned above), are there grounds to expect that either the heads now have warped and should I replace the rings? I do not know the size (thickness) and matter (steel/titanium?) of the rings. The engine was saved and only seems to have loss compression . Is this due to the possibly warped heads or to the rings? How can I test compression to solidify the fact that it is the rings (diesel engines do not have spark plugs to take out in order to test compression)? I want to know BEFORE I break the seal of the oil pan. BTW, after taking off the heads, all 3 cylinders travel prefectly to TDC/BDC...there is no possibililty of warped cylinders or connecting rods and there is no discoloration (burn marks) or "bumps" inside the cylinder walls.

Thanks,

David

 

[zjakopovic]

Compression on diesel motors is measured via injector holes (equvalent of spark plug holes on gas engines). Ask your closest Zetor dealer, or any guy who has repair shop for injection pumps, for "blind injector" and pressure measuring device. Normal pressure has to be between 22-30bar (320-440psi).

You need to dismount injector holders on all heads, install "blind injector" (need to have similar shape to original injector holder), connected to pressure measuring device (usually with paper tape here, to print max pressure on each cylinder), and crank engine with starter.
This procedure need to be carried out for every cylinder.

I had similar overheating experience on my ex car (Yugo, gasoline engine). After overheating, it blowed oil out through the oil pan breather. We just replace piston rings, an everything was ok since then.

Hope this helps.
ZJ

 

[zjakopovic]

And yes, you're right. Zetor engine doesn't have glow plugs in heads, as they don't need it. They start fine up to freezing fuel

 

[twinpartners]

Excellent! Thanks ZJ! Will keep you posted on the outcome. Blind injectors may be hard to come by...my local dealer won't sell me theirs cause its the only ones they got. He said that I can't order them either because only official Zetor distributors can get them. Depending on the cost of a fuel injector, I may buy a "real" one and fabricated a dummy out of one of the old ones.

David

 

[Renze]

Heads bend due to heat.. Yes cast iron is heat treated, not to make it keep its shape, but to settle the carbon elements in the mulecular structure... when you cool it down rapidly, the steel will be a few % bigger than when it is cooled down slowly, because the carbon molecules are trapped between the steel molecules instead of inside of them.

Your quickly cooled liners are bigger than original.

For the same reason, a heat treated/hardened front axle pivot bearing can easily be pulled out of a casing when you weld through it and let it cool down slowly, because it will shrink and loose its hardness at the same time.

Anyways if you know what you're talking about then follow your own convictions ?

BTW i could write the theory from mu materials book here if you wanted

 

[twinpartners]

To all who are interested:
My neighbors friend is a diesel mechanic and brought his dummy injector set and we got a reading of 26, 28, 27 on the three cylinders respectively. (Thanks ZJ!)

I replaced the head gasket, intake/exhaust manifold gaskets, exhaust u-joint gaskets and the rubber valve cover gaskets. This comes as a complete kit from Ridgeway Enterprises www.zetorusa.com for around $40!

Sorry that you all had to hear about molecular theory, axle pivot bearings and the Murphy's Law of Garden Hoses and Engine Blocks. I personally don't think it was needed.

 

[zjakopovic]

So, I didn't told a house numbers for cyl pressure (goood)
Lowest compression was on first cylinder (front end on engine)?

Not a bad molecular theory. Just a stupid question: How can I use garden hose on air cooled SAME engine ??? JOKE!

Glad to help you