We have a '05 Cat C7 acert in a bus at work that is burning coolant,has severe blowby and is trying to hydrolock after sitting over night. Originally it came in with the crankcase full of coolant so we changed the oil and refilled the coolant tank,and after we topped off the coolant it hydrolocked. So far we have replaced the hg,machined the head,and replaced injector cups. It ran good for about five miles and now we are back at square one. Does anybody have any other suggestions on what could be the issue? It did have alot of pitting in the coolant passages so is it possible that a cylinder might have cavitation?

 

sorry,but it soundslike liner o rings.drop the oil pan and pressurize the coolimg system and look for the cylinder that is leaking.good luck

 

I was hoping for it to be a liner o-ring but I got it apart and it doesn't have liners in it. While it was apart I did noticed it had very little crosshatching left in the cylinders.Is that normal for only having 110K miles?

 

I made a post stating that there were no liners in the C7. I am not sure but I do believe that there is some type of liquid to exhaust cooling either for the turbo or for Cats version of egr. Your problem may be within that system.

Are the cylinder walls polished real shinny?

Not sure what happened to the reply I made yesterday?

 

The walls are a dark gray color with smooth blue spots here and there. Before we tore it down it would spew a quart of oil an hour out the blowby tube.

 

I will make a couple calls for you tomorrow. I have a life long friend that is the service manager for a local KW dealer. His specialty has always been Cat motors.

How did the pistons look when you pulled the head? Were the cross hatch marks gone on one side of the cylinder wall but not the other on any of the cylinders? What did the coolant look like? Was there any thick pasty substance in the overflow tank or head passages?

 

Thanks. The coolant looked like mud and everything it came in contact with is pitted. All the cylinders looked to be in the same shape but all the pistons had the injector spray pattern etched in them pretty good.

 

Nope, No liners on a C7.. its an intergrated bore block. When the engine was running with coolant in it, did the engine spew coolant out of the overflow or were you getting compression back into the cooling system?
Next, did you happen to pressurize the cooling system and look for leaks? If you can pressurize the cooling system with the intake piping and exhaust manifold off, it might help..
Does the engine have an air compressor? that part can be bypassed to ensure that its not part of the issue. I have found some C-15 and C-18's where the inlet for the air compressor is being pulled from the inlet air piping. If the compressor fails internally, sometimes it can start pumping coolant back into the intake... Sorry, I dont work on buses, so im not sure how your application is set up... Just throwing out ideas..
You might try filling it with coolant and pulling the injectors. Allow it to set for awhile then spin the engine over. Do this several times and see if it always comes from the same hole...
Last one of these little engines I worked on had about 175 hours on it and had a split #2 cylinder wall...

 

You say the coolant looked like mud. I would almost say you are a victim of mixing non compatible coolant. Not saying you did it, but someone did.

When I run into a situation like you describe, on a cat especially, I get the engine warm, then take the intake pipe off, and watch for steam. 99% of the time, I get to see exactly that. I then run a borescope down into the intake runners, and look for the bright coloured waterfall above the intake valves.

Since you are past that point of ripping it down, I would get the head pressure tested at, or close to operating temperature. I am thinking your problem will show up.

Good luck

 

Just to add to what Pind said, exhaust gases mixing with coolant will present with mud for coolant also.

 

Could be EGR cooler failure, if the ACERT includes cooled EGR. Not sure if it does..

 

Actually Tim..... ( gotta use that one)

So will oil, when mixed with ELC. and it muddies up the cooling passages in the head first. When you remove it, after being heated, it looks for all the world like jello. Even tastes good.

A lot of the head failures that I have seen on diesels, are a direct result of oil coolers failing, and allowing oil into the coolant, the old green coolant would handle this to some extent, and you could clean it out, but even a hot tank won't take the jello out of the block and head with the ELC. You have to do some pretty impressive HIGH pressure, HOT washing to get it all out. And where it clings, you will get hot spots.

 

As a matter of fact all the c-7's we have in the fleet have experienced an oil cooler failure.Its also very possible that the coolant has been mixed with green. I did find the reason for the worn cylinders though, a couple times it went over 35k between oil changes on some very cheap oil.

 

It never did blow coolant out the over flow,it does build pressure while running, and when you pressurize it it partially fills one of the cylinders with coolant.I didn't think about the compressor being bad thanks for that tip.