I’ve got a very small coolant leak that I’ve been unable to find the source. I’m finding coolant on the air conditioner compressor and serpentine belt, so the leak is somewhere forward and on the passenger side. I’ve check the coolant tank, hoses, water pump, freeze plugs and found no source. The leak is very small but needs to be found and corrected. Any ideas that I might have overlooked? I’ve been to the local parts store twice to rent a coolant pressure tester…but haven’t found the correct screw-on connection to use the tester.

 

I had a similar leak when my truck was brand new ( years must be passing so fast !) . In my case, it was a bad radiator cap and dealer changed it under warranty ( and put a fluorocent die material into the radiator for detecting the source of future leaks) . So many years passed ever since , and did not have any other coolant leak . Hope yours will have a simple solution too, good luck.
Ken

 

That's the first thing I thought of was the reservoir cap. How full is the reservoir?

 

Coolant level is at the low level mark on the side of the tank. Not sure how coolant could get out the cap without covering more of the engine...but that would make sense because there is NO path for coolant to get on the A/C compressor. I'll swap out the cap and see if that make a difference.

 

The next thing is radiator (tank-to-core) leak.

 

That would be the tank seem?! If yes, you would think I would have coolant directly under the radiator, there is none.

 

Hate to say it, but you sure it's not a head gasket?

 

I've looked...closely but haven't seen any signs. I won't rule it out at this point. I'm going to try the radiator cap first. If that doesn't identify anything I'm going to pull the fan, fan shroud, and belt so I can get in there and get serious. I'll keep you guys updated.

 

Do you have a heater control valve on your truck? I've had them produce slow leaks on other vehicles. Some SDs have them and some don't. I've also gotten leaks at the hose connections. I usually replace the factory steel clips with stainless hose clamps.

 

This is self serving but what the heck. I was reviewing all of the motor pictures in my albums and think it's got to be something forward of the motor. The leak on the A/C compressor is on the clutch/belt area not further back which might indicate a head gasket. Does the water pump have two tattle tail ports? I can only see the one near the top and it's dry, I'm not able to see the bottom side of the water pump because of all the pulleys. I don't know?

 

Yes, I did install a heater bypass valve and had to replace both hose clamps on the front side of the manifold, the factor clamps wouldn't hold anymore. However, that's not where the leaks at and everything up top is dry. I have coolant on the stud bracket between the balancer and A/C clutch, also on the A/C clutch itself. Then some coolant on the frame where the A/C clutch slings it off onto the frame.

 

I do believe there are two weep holes on the modular engines' water pump. I replaced the one in my wife's Cougar 4.6L because it was squeaking at an early age, and I was surprised there were two on the OEM pump. One on top, one on bottom.

A somewhat easy way to tell if the pump seal is bad is to take the belts off, and rotate the pump by hand slowly and let go. If the pulley tries to rotate back just a smidge by itself, it means the seal is grabbing. When you do that with a pump that the seal is leaking, or the bearing is bad, it won't have the little bit of "give back" to it.

 

Interesting! I ruled out the water pump because I could see the top weep holes was dry! This information would put the water pump back in the running as a cause. I'll dig into that piece of information further.

 

Conversely, the water pump spins counter-clockwise (backside of the belt) so it would probably fling it onto the power steering pump

 

UPDATE: I replaced the radiator cap and monitored. At first I still had the smell but no more fluid. After almost two months and a trip to Taos NM for skiing and fun...no fluid loss, smell is gone! Thanks for all the input hopefully this helps others in the future.