03 leaking coolant at radiator area, but quits when warmed up, and is always full?.

[GM Guy]

My boss' 03 cummins has developed an issue lately, and it is quite worrysome.

Whenever you fire the truck up, and while it is warming up, it pukes a little bit of coolant out. but when it warms up, it doesnt leak. It will also not maintain bottle levels, yet the bottle doesnt looked cracked, nor does the hose connecting the rad and tank.

Another issue occuring is that when he is pulling it hard, it wont maintain specified temp, it usually goes up to about 210, but no higher, and then it will cool down to spec, then back up. He has changed the water pump and t-stat.

So what do you guys think is wrong with the ol gal?

 

[NVW]

My guess would be head gasket, I have no experience with cummins but in the cold some diesels will slobber and leak coolant until things expand when warm.

 

[GM Guy]

boss and I are wondering if the OEM radiator is starting to leak a little at the end tank core connection, and when it warms up, it swells and seals. I guess that would make the most sense, since it has never been ran out of coolant, or been chipped. So i think head gasket may be a possibility, but wouldnt it bubble in the radiator?

 

[Cumminalong]

Okay, he's already replaced the water pump and thermostat, so the next place I would look (actually, this is the first place you want to look) is the coupler that is located right between the turbo and the block.

There is a short (approx 3") coupler that joins the coolant lines and this is known to leak, especially in the spring and fall as the temperature change.

The next spot I'd look is where the heater core line comes out of the head. The inside of the fitting is kind of sharp and can cut that line.

Now, here's where it gets ugly.....

The next most common problem is the coolant and trans cooler lines cracking and mixing fluid. The tranny heat exchanger coils were intermixed with the coolant coils and this has been known to casue mixinf of the two fluids....not good.

Check the tranny fluid and see if it's at the right level and also check the coolant for signs of contamination by the trans fluid.

 

[GM Guy]

it is a 6 speed manual. These are not like the ford ZF6s that have a cooler are they?

the thing that gets me is that the leak comes out from right under the radiator, so I would thing it would have to be a radiator, wouldnt it?

 

[Cumminalong]

Okay, didn't realize it was a 6 speed.

If it's coming from right under the radiator, then that's the likely cause BUT don't under estimate that the water pump was bad out of the box either....especially if it was an AutoZone or Advance Chinese made POS.

We see very few bad radiators, but replacing water pumps, while not overly common, is much more frequent than the rad's are.

I can honestly say, we've never had a Cummins come into the shop with a bad radiator.

Lemme ask this, has he replace the cap on the radiator?

 

[GM Guy]

possibly, i would need to ask, but i am 80 percent sure he has changed the cap.

 

[GM Guy]

its been a while, but i figured i better wrap up this thread. He changed out the radiator, overflow tank, and flushed the coolant. It seemed to fix the problems he has been having.