cant find coolant leak. 95 Chevy Cheyenne

dtransport

I have a 95 chevy cheyenne 2500 5.8 pick up which I want to hold on to even if its old. I was driving my truck and it would start to shake then shutoff the temperature needle would go all the way to the overheating numbers then come back the heat would blow and then get cold..later I put coolant in the radiator and the reservoir and everything is fine. A few days later my heat blows between hot n cold and the n temp needle goes alil high but not completely to the overheat side. I look n see i have no coolant my reservoir is empty and my radiator is empty I cant find the leak but there is a wet stream that kinda smells like coolant dripping down from the radiator cap..is it possible all my coolant jump out of there?..any suggestions..thanx

bpeebles

It is possible you did not "burp" all the air out of the cooling system. Just filling the radiator and overflow tank is NOT sufficient. (There will still be air in the system) To get all the air out, you need to check and top-off the overflow tank EVERY morning for several days in a row. Each time the engine cools-off, it sucks more fluid in from the overflow tank.

If, after doing this, you still seem to be losing coolant, read on:

Not all coolant leaks are to the OUTSIDE of the engine. Coolant may also leak into the OIL or into the cylinders. (hence going out the exhaust as steam)

If leaking into the oil, the oil on the dipstick will be 'whitish' colored. If leaking onto cylinder, the engine may be hard to start and may blow steam out exhaust when started.

At that point, you may need a "Leakdown Test". (When the engine is HOT) This may be the only way to diagnose a head-gasket leak that only happens when the engine is hot (metal is expanded)

ray80

I believe there may be bleed valves also (2) that may assist in ensuring all the air is out of system, re-fill as needed (then watch to see if its really losing coolant, new pressure cap may help also)