MEP-803A overheat - newer issue

[k9medic]

I appears that I post about every 6 months or so, after I have been to my place in the islands and had to fight with the generator. This time is no different.

Finally got back to the islands over the past weekend. Ran the generator for a bit without a load and put in some radiator flush. After about 2 hours of running without a load, I drained and flushed the radiator getting a lot of black liquid out. I then filled the radiator back up and started it up with a load. After running about 10 minutes with a load of 18.6 amps on line 1 and 19.4 amps in line 3, the generator over heated and shut down. Thankfully we had "normal power" with no issued on this trip and didn't have to rely on the generator.

Here is what I found while checking things -
1. half of radiator fan shroud is missing (but it has been missing since I bought it and I have not had these issues in the past really.)
2. Both of the radiator hoses feel "crunchy" when I squeeze them. They are not soft and pliable.
3. fan spins with the water pump and no damage to the fins.

confirming there is not an internal impeller in the water pump?

Followed the following from the manual -
1. amps don't appear to be more than capacity
2. coolant level is full
3. pretty sure oil level is good but I didn't think to check it
4. didn't check the air intake
5. fan belt is tight



Any suggestions? We hope to be back at the end of December.

 

[Ray70]

First thought would be a stuck thermostat. Any idea if the upper hose was excessively hot when it shut down or still cold / cool?
Also, was the temp gage pegged right?
First you should verify the engine actually overheated and the issue isn't a faulty sensor.
Then verify the hoses and radiator are HOT. If not, the thermostat is most likely either stuck shut or you got an air pocket stuck behind it when you changed the fluid. The T-stat will not open correctly if not exposed to coolant, such as when air gets stuck behind it.

 

[k9medic]

First thought would be a stuck thermostat. Any idea if the upper hose was excessively hot when it shut down or still cold / cool?
Also, was the temp gage pegged right?
First you should verify the engine actually overheated and the issue isn't a faulty sensor.
Then verify the hoses and radiator are HOT. If not, the thermostat is most likely either stuck shut or you got an air pocket stuck behind it when you changed the fluid. The T-stat will not open correctly if not exposed to coolant, such as when air gets stuck behind it.

Forgot to mention that I pulled the thermostat out too. It was absolutely an overheat as the coolant was bubbling out all over.

 

[Dieselmeister]

It was absolutely an overheat as the coolant was bubbling out all over.

Need to make sure it was hot! A bad head gasket ( or worse) can blow coolant all over the place also. The reason I mention that is, you stated you got a lot of black liquid out of the radiator. Usually it is antifreeze color or rust color for really old antifreeze, not black. The crunchy hoses could be the springs inside the hoses that keep them from collapsing. The springs in mine were rust particles holding hands. After I squeezed the hoses, they completely crumbled. (Note I have an 802, so your hoses may be different).

 

[k9medic]

The hoses did feel like there were springs in it. The coolant was hot and boiling. Not bubbling like it was pressurized.

The black liquid was from the radiator flush. I drained the radiator and filled it with water and the solution per the directions. Ran it for the required time with no issues overheating and then flushed it and refilled.

 

[Ray70]

So you pulled the t-stat, flushed motor, replaced t-stat and new coolant, then it overheated??

 

[Zed254]

A 'minor' detail bit me one time. I had overheating problems when I put too much antifreeze in my 803. Once I got the mixture correct - 50% antifreeze / 50% water in my case - all was as it should be.

 

[k9medic]

Pulled, flushed, did not reinstall t stat and then new coolant and it overheated.

 

[Ray70]

Running it without a thermostat could very likely be the cause of the overheating. It may seem contradictory, but without the thermostat to regulate the flow, water will circulate too fast and not transfer its heat properly.
Excessive levels of antifreeze and insufficient water will also cause overheating because the antifreeze itself does not transfer heat very well, that's what the water is for.
Put in a new 180* thermostat, keep the mixture around 50/50 and no stronger than 60/40 and retest.

 

[m32825]

How do you tell if the radiator itself is clogged?

 

[Ray70]

It's difficult to tell the condition of ALL the tubes, but if you disconnect the lower hose and stick a garden hose in the top at full open you should have full flow out the bottom, it should not be restricted and forcing pressure out the top.
You may get some splash-back out the top because the filler neck makes an immediate 90* bend into the radiator, but other than that it should flow right through, wide open.
Kind of crude test but should get you in the ballpark.
You can also stick your hose in the bottom, seal it as best you can, then flow it backwards out the top, this will help backflush anything stuck in the tops of the tubes.

 

[Guyfang]

Lets see. You run a get set with no thermostat. You run the set for two hours and drain the radiator clening crap out, and only flush it once. You run a generator at a fairly decent load, without checking the oil. Half the radiator shroud is missing. A shroud designed to help keep the gen set cool, and wonder why it over heated? Why do you think the thermostat is in there? You need to go back, and start from squair one. Put in a know good/new thermostat. Flush the radiator 2-3 times with water. NEVER start a set without checking the oil. Try and find/get the fan shroud. If you can, test the temp with a thermo gun, at the thermostat housing.

 

[jamawieb]

I would say you have air in the cooling system. If you don't get the air out it will overheat because the fluid is not flowing. Try taking the top radiator hose off and refilling through the hose. That will push all the air out the cap or thermostat housing.

 

[Daybreak]

Howdy,
A flush always include flushing thoroughly multiple times.
Re filling trick too.
When putting in good coolant, fill it up, hit the dead crank some, and fill it more, hit the dead crank some, and fill some more. I also find tilting the entire unit over some to make it easier to fill fully.

 

[Ray70]

Another helpful trick is to drill a 1/8" air bleed hole through the flat section of the thermostat. Some better brands come with a hole already there with a little loose fit captive pin that will seal it once pressure builds.
This allows the air to pass through when filling, but 1/8" is small enough that it won't affect performance at all.

 

[cuad4u]

It's difficult to tell the condition of ALL the tubes, but if you disconnect the lower hose and stick a garden hose in the top at full open you should have full flow out the bottom, it should not be restricted and forcing pressure out the top.
You may get some splash-back out the top because the filler neck makes an immediate 90* bend into the radiator, but other than that it should flow right through, wide open.
Kind of crude test but should get you in the ballpark.
You can also stick your hose in the bottom, seal it as best you can, then flow it backwards out the top, this will help backflush anything stuck in the tops of the tubes.

IMO - Most radiators flow hot water from the engine in the top of the radiator to the bottom where the cooler water goes back into the engine. In some applications the reverse is possible. If crud is on the flues in the radiator, (again IMO) open the top and the bottom hoses. Make an adapator (duct tape can be used in a pinch) and attach a water hose to the bottom radiator nipple and flow water from the bottom of the radiator to the top. A lot of volume of water is needed. If crud is on or in the flues, the back wash will do a better job in breaking loose the crud when flowing against the direction that the crud formed. Any way, it is worth a try.

 

[k9medic]

Okay... I'm back again... Had a chance to finally spend some time working on the unit.

Flushed the radiator again. Filled the radiator and burped it several times. Filled the engine oil. Replaced the radiator shroud. Replaced the thermostat.

The unit runs like a top while unloaded. When I put a load on it (3 mini split AC units that pull a total of 25 amps) it runs for about 15 minutes before overheating.

Looking at the TM's my next stop is a water pump replacement followed by fuel pump timing.

Any other suggestions?

 

[Ray70]

So after 15 minutes the temp gage is assumingly pinned all the way up? and you start puking antifreeze out the overflow?
Are you getting an over temp fault light?
I know you mentioned it was hot, but just trying to rule out cylinder pressure getting into the cooling system and over pressurizing the radiator cap, causing it to puke 190 degree water due to pressure rather than temperature.
If you have a laser or IR thermometer, check the temp on the side of the block to confirm the temp.
Also try checking the exhaust ports on the head and the valve covers. If you have leaking injectors that are dripping excess fuel into the cylinders your exhaust temps will get very high pretty quickly and you will probably notice the head and valve covers getting hot excessively fast.
You could remove the radiator cap and the overflow tube and start it up. cover the radiator with the palm of your hand and a finger over the overflow tube.
Let it run a couple minutes at most and remove your finger. Did you feel pressure being released? If so I would suspect a head gasket leak.
If not continue on with water pump inspection.

 

[k9medic]

Yes. Overtemp light. Hot spewing radiator fluid everywhere. No coolant in the oil. I do have a head gasket leak detector I could bring over.

Unfortunately, getting time to work on the darn thing is a PITA. I went ahead and bought a water pump. I figure for $150 I could at least eliminate that variable.

 

[Ray70]

Gotcha... well, yank the water pump and see if you have an issue with the impeller.
When you reassemble pay attention to the O-rings on the cross over tube.
Clean the rust out of the head and interface plate where the O-rings sit and lube the new o rings a little.
If you reuse the old o-rings, put a little gasket sealer on them, otherwise used o-rings tend to leak in that spot.