I consider myself fairly knowledgeable about cars but checking the coolant always seems to confuse me. I have a 91 4runner v6 4x4 manual. Right now the engine is warm and the level in the over flow tank is nearly empty. Is this normal, or should I fill it up? From what I understand the coolant normally in the overflow tank gets sucked into the radiator to help cool the engine when it warms up, right? The coolant level should be good as I checked it a few weeks ago, and after inspecting all hoses, caps, water pump I don't see any leaks. Thanks for any help guys.

 

The expansion tank serves a few different purposes, but that is one. I think you're fine.

 

Here's a good explanation..........

http://www.carpartswholesale.com/cpw...flow_tank.html

 

Well, dang.............that's a good one, too. <<tip, tip>>>

 

Yota4 X2
So if your expansion tank was full (or 1/2 full when cold) a couple weeks ago and now its empty then you have a leak. Or it is possible there was air in the system that got burped out which created a vacuum and sucked dry your tank.

 

yes anytime the system is purged of air (burp) it will suck in more coolant from the overflow tank

 

I would make sure you are checking the level consistantly and make sure you have a good rad cap. If you check the level each morning when the engine is cold you will know after some time if there is a leak or not. As stated above, the min/max level in the expansion tank is for a cold engine, so checking the expansion tank when the engine is hot is meaningless.

 

Thanks for the help guys, I'm definatly going to look into this. When I refilled the radiator after getting it repaired I had the cap off and the heater on with the engine on to burp the system, and I've already had the headgasket recall done. I don't see any leaks so I hope it isnt another internal leak lol. Please, pray for me, lol jk

 

I am having a similar problem. Ever since I did my timing chain about two moths ago, I have had to refill my coolant reservoir probably three times. So assuming i do have a leak, what are the likely culprits?

Could it just be a bad radiator cap? I replaced all my hoses and none of them show any signs of leaking. And the I see no evidence of leaks around the timing chain cover, though I suppose these might be hard to see.

 

As far as I know, (feel free to chime in if I am wrong guys), If no external leak is visible then it would be an internal leak, ie blown head gasket or something else serious. It would be a good idea to pressure test it, I did that about a month ago and found my radiator leak, but with this coolant situation I may need to do it again. Either way I am going to check and refill it when my engine is cold and go from there.