Hi all, new to the forum. This looks like the right place to ask, since I don't see a 5.7 or V-8 forum. In my 1999 Suburban with a 5.7, I am losing coolant at an amazing rate, but there is no fluid on the ground. The oil is not milky. I am running a synthetic oil. I state that because I don't know if synthetic's have a different look when they get water in the oil. I am adding about a gallon a day. The other day I put my hand in front of the tail pipe while it was running and the exhaust seemed real damp. Could that much water be getting "combusted"? One thing makes me think the coolant might be getting digested is that the engine idles a little rough. I think most would agree these engines run perfectly smooth when they are right. The engine and transmission has 200,000 miles on it. I use it for towing a 25 ft. trailer andregular "family" dutys. The transmission still seems to work perfectly, but I am pretty sure I will be putting in new Good Wrench engine and tranny with in a month. How hard is it to disconnect/reconnect/purge the fuel injection? Any help and pointers would be appreciated.

Eric

 

The best way to find out coolant leak is to do a pressure test,it will reveal the leak. (Do it when engine is cold )
Are you sure it is not geting mixed in transmission fluid?
did you notice wetness near heater core?
Is there white smoke ?

Is your truck overheating?

 

The temp needle floats around when the coolant gets low. I have kept a real close eye on it though. Hadn't thought about the trans. I don't think the leak is on the out side of the engine. I would think if it is losing over a gallon a day and you don't see any evidence.....I have not yet seen any white exhaust, just seemed to be real damp when I put my hand near the tail pipe. I did change the radiator recently. I wonder if there is leak in one of the coolers?

Eric

 

If it is leaking in transmission cooler,the ATF will become milky.Do a pressure test and let us know,from where you found the leak

Do not give pressure more then specfied on label or radiator cap.otherwise you may create new leak.