Coolant disapeering - LS400

[lemonhead401]

I have a 1990 LS400 and coolant disapeers while the engine is running. The car runs great, no clunking or steam out the back, but when the car is driven coolant seems to magically disapeer. There are never any puddles on my garage floor and it doesn't run hot. Also nothing drips when I let it idle either. I have looked in the engine and there is no residual coolant anywhere on the engine but every time I open the hood I add about a half of a gallon (about once a week). When I first found the problem I added a whole gallon and a half and blead the system. The cooling system was pressure checked and the only leak was a crack in the expansion tank which I reapaired and it no longer leaks. I put some radiator stop leak in and that seemed to slow the problem but coolant is still disappearing. Any ideas?

 

[striker]

Pull your oil-dipstick put a lighter underneath the oildrip and if it starts to make crackling sounds it's bad. this trick shows any water in you oil, in which case it would be new head gaskets.

one other thing: are you sure your coolingsystem presurises itself when hot? if not there's a leak somewhere and you'll loose water through simple evaporation.

grtz thomas

 

[jibbby]

That happen with my Toyota Landcruiser recently...It was the radiator cap and over spill that was the culprit for the coolant magically dissapearing...I got a new radiator cap filled it all up again and it was fixed...

The radiator cap is spring loaded for pressure...If that spring goes so does your coolant on some cars, and it is a very slow process.....I am guessing that may be your culprit...

 

[B-FISH]

I Have Somethin Like This Going On But My Car Does Get Hot, But Then It Drops, And So On....i Can See Steam Coming Out Of The Overflow Tube, Do You Think A New Cap Can Help Me Out???