i was just doing an oil change on my 94 pickup w/3vze and noticed the radiator has no visible fluid in it. the overflow is full. should i top the rad up?

the engine was cold by the time i checked it.

the temp gauge seems normal and the truck runs fine.

 

Was the top of the radiator visibly damp? Top it off from some of the overflow so the overflow is at the proper level. Recheck when warm...not HOT or you'll get a facefull.

 

That's what's usually recommended. Gotta leak somewhere, do ya?

See if the cap needs replacing.....cracked gasket, maybe. Do you ever notice a coolant smell when the engine is hot?

 

nah, no coolant smell ever. top of rad core was definitely damp, and the overflow was at the proper level. no leaks either. i'll check again when the truck is warm sometime, but i'm thinking this a case of "if it aint broke" ;D

 

it should be sucking stuff from the overflow back into the rad. usually it can get down a little, but not much.

 

Well, loss of coolant means a leak somewhere either externally or internally. So....

 

probably. depending on how low it is it could just have gone into the expansion tank, and not got sucked back into the rad when it all cooled down.

pressure test time

 

If your rad cap is working properly, coolant will flow from your cooling system to your overflow bottle when your engine heats up and the coolant swells. When your engine cools off again, and the volume of coolant in the system shrinks, the rad cap should allow the system to suck the coolant back into the system from the overflow bottle.

Are you sure the little hose that goes into the overflow bottle is in good condition? No splits in the hose either between the rad and the overflow bottle, or above the water line in the overflow bottle? Is the hose clamp on tight where it attaches to the radiator? Any air leaks will suck air instead of coolant into your system when your engine cools down.

 

Also check that the hose to the overflow bottle isn't blocked.

 

the other thought is the seal on the rad cap. if it doesent seal it wont create suction properly.

how much did you need to add to get it back full?

 

My radiator was leaking from the neck joint between the cap and the radiator. I used a torch and soldier to fix it going all the around the neck.

Now the radiator holds proper pressure

 

my truck did this as well....after searching the front end, i found that the water pump was leaking. It was a slow leak and only after the engine was hot and then turned off and let sit. It would dump coolant for the first 10-20 minutes after a drive and then be done. Replaced the water pump and it hasn't leaked since. And no, the temp gauge never got above normal...

 

i don't see any leaks on the ground, so if it's leaking it's leaking internally or sucking air. i haven't topped it up yet, but i'll check when it's warm. there's definitely air in the system somewhere as i hear a gurgling noise when i first turn on the heater.

i guess i'll fill the rad and burp the system and check all the hoses for tightness.

thanks guys

 

hmmm... I just assumed when you said that the overflow was full, you meant right to the top. Did you mean it was at the "full" line on the container? My post from above only really applies if it was over-full. If it's at the full mark when the truck is cold and there is not coolant right up to the top of the radiator, then one of three things is going on:

1. External leak, which you say it isn't.

2. Internal leak between a coolant passage and combustion chamber, which means headgasket is leaking somewhere, allowing coolant to make it's way into a combustion chamber. Small leaks are hard to diagnose unless you perform a leak down test.

3. Whenever your cooling system was last flushed, it was not properly burped, and now the air that was once trapped somewhere in your engine has made it's way to your radiator. This cushion of air allows room for you coolant to expand when it heats up without increasing the pressure as much as if your system was filled with liquid. This could be the reason that your rad cap hasn't opened and allowed that air to be expelled from your system.

An easy test to try is refill your rad and ensure that your system is completely burped, close it up, then keep an eye on it for the next little while. If the level goes down again, #3 isn't your problem.

 

good advice. i'll burp the system and see if i can borrow a leakdown tester. there's no real blown hg symptoms (oil is fine, coolant looks fine, no steam out of exhaust), so hopefully it's an air bubble. the reservoir is only full to the full line.

 

Cool. Keep in mind that small HG leaks (directly to the combustion chamber) don't always offer up symptoms. Cooling system to oil system leaks are typically quite obvious.