Does anyone on here know the 5.9 cooling system well. I came up with a simple problem and I am wondering if this is what happened to my motor. The bypass hose on the 24v is internal, under the thermostat. I had put a new thermostat in the engine a month or so before the engine went down. The thermostat was purchased on August 18, 2003 and would have been installed in the next couple of weeks or more.

Installing the new engine I had decided to put in another thermostat just sop and I thought that the one in it was a little lumpy. When I took the elbow off the thermostat came out and left the bottom valve in the engine.

I spent some hours inspecting and pondering the cooling system, also reading in the service manual. As I understand how it is working, when the thermostat is closed the valve at the bottom retracts and allows water to bypass and circulate in the engine. When the thermostat opens, the valve disk on the bottom of the thermostat lowers and closes the bypass passage.

With the disk broken off, the disk and some other parts, were firmly over the bypass port and the water pressure would hold this to the port thereby closing it permanently. Now, my question is this, do you think that the bypass being closed would cause an over heat problem in part of the engine?

The Cummins representative said that this condition was caused by not enough coolant at #1 cylinder. I could not really see a reason for this before. But looking at the system, the temperature gage is above the thermostat so with the bypass closed it would not read the temperature of the engine. (take note of change coming) On a cold day, the conditions that it went down both times, the cold air on the radiator closes the thermostat and then while pulling a load, the engine does not get circulation until the thermostat opens again, and the gage is on the top side of the thermostat, before the bypass. With the bypass closed the hot water never reaches the gage or the thermostat to open.

OK guru's, does this sound like a possibility? Did I lose about $10,000 and weeks of lost work because of a thermostat? When overhauling the engine, I never pulled the thermostat out of the head, but this time I am going over each thing possible to find out why the engine went out twice from an overheated piston.

I also noticed that the new thermostat is a totally different design with actually a little smaller flow. But is designed to eliminate the possibility of the disk separating. I will have picture of this and will post them but cannot make them smaller.

 

I just looked at the cooling system schematic and I think you hit the nail on the head. When the thermostat was closed, you were getting NO water circulation at all, you were probably getting boiling at any hot spots and the engine was overheating even though the radiator was cold. 2 rebuilds over a thermostat, dang that's downright aggravating!

 

Yeah and the gage is in the thermostat housing, not the engine side, no circulation and the thermostat would not open right, which I noticed. That would be the trapped air at the high point of the block, cylinder number one.

Using genuine commins parts, I wonder if I have legal recourse.

 

If you can prove this you certainly have a position. You need to document and provide a reciept for the thermostat and then I think tou have an issue with the manufacture of the thermostat. It may take a lawyer to go after it but the right one if you can prove responsibility could possibly get the repair cost and lost wages. I am not a lawyer so this is just my opinion

 

This is the thermostat in two pieces.

 

This is the bypass port opening.

 

This is how I found the bypass port when removing the thermostat.

 

It looks like a thermostat failure would block both ways for the coolant- A the internal bypass and B the route through the radiator. This would lead to a no flow situation at the temp sensor and the thermostat. Therefore the temp sensor and the thermostat will act on the temp that results from the block carrying heat forward and the ambient air cooling it. Even if you put the sensor on the other side of the thermostat you'd still have no flow and therefore irrelevnt temp readings.
I'd suggest that you mount a sensor in the water jacket of cyl. no 1, close to the head. A metal contact temp sensor on the cylinder liner would even be better, since this is the temp that went out of range for you, and therefore this one should be monitored. Naturally the readings and the critical values would be different for this sensor than for the stock temp gauge.

Sorry to hear about your bad luck, I wish you a successfull recovery of those losses.

AlpineRAM

 

Out of curiousity for the rest of us, any idea when the "redesigned" thermostat started showing up in CTD's? Presumably after 1999. . . .

 

Dang, that's a goofy place for the temp sensor. My old Ford had the sensor in the thermostat housing (engine side) for the computer, and another sensor mounted in the block for the guage. That was a good setup.

 

No idea of dates except that the bad design was purchased August 2003. I have had several in the truck, the original '99 would overheat on pull, changed it for a 180 degree and it worked well. Put a 190 in for a winter, then went back to a 180. Last fall I flushed, installed a new thermostat, and new coolant, which was the bad thermostat. I really do not remember the different designs except that the bad one is very different than the newest one purchased the last couple of days.

 

Thats right Marcus, and when I did the overhaul, I never bothered pulling the thermostat because it was only a few weeks old. Big mistake.

 

Haulin in a way I am glad you did find the problem. Bad that it happened twice but at least now you know the cause. Are you sure the 'stat is for your specific vehicle?? Not the first time a parts person has grabbed the wrong parts.
What's with the Freightliner cam??

 

Spots the thermostat was purchased from Cummins and was a good fit, worked fine when installed, was a lousy design that they have changed. There must be more of them out there.

The engine was a 24 valve, built to the specs for Freightliner. Different timing case, center sump pan, completely different plugs and acessory mountings. It also has the cam that is a higher bottom end torque but will not be as fast empty 0 to 60. The injectors are smaller flow and slow. It had the SAE bell housing on the back. I checked all the specs, the pistons, rods, crank, and so on are the same as the Dodge unit, the cam is different. Should be better for my use. The broken injector pump unit was a 2500 rpm unit. Yes, the valve springs are the same. Checked with a backyard torque on the rocker arm home made device. A hook welded to a socket and a torque wrench. Hey, for comparitave purposes it did fine. I also got to drive one that had the same conversion. Ran great, stronger on the bottom, weaker on the high rpm's. Fell off after 2700. With the six speed that is just fine.

 

Do you know the part number for the bad thermostat? and the # for the redesigned one?

when pulling, my temp rises to about 200. I want to change to a new 180 Deg. thermostat, but I want to get the right part number...


If you have already posted this, im am sorry. I must have read over it.

THanks, Phillip