Disappearing engine coolant

HELP! I have a 2003 Vovlo XC 90, which has had way too many problems AFTER the warranty expired. The latest proplem is that the coolant is disappearing. There is no evidence of leak, and the engine seems to run fine. The coolant system was pressure tested and seemed fine. I’m ready to junk the car…i am so, so sad about this, as whatever it is, i’m sure it will be as awful as the other problems (bad wheel bearing, and bad water pump)…the car has 76K…i expected a lot more!

check oil on dip stick and if looks milky and just not plain oil you have a bad head gasket. you will get a gray smoke coming out of tail pipe, have shop check for this . they use a couple different methods. not sure about the cost 4cyl around $800 v6 maybe $1200. since you did say any thing about over heating your heads may not be warped. watch for overheating. look under cap were oil is put in also.

What boxwrench said is right on. I would add that pressure testing the coolant system won’t necessarily tell you if the headgasket is blown - you need to test the engine cylinders to see if they are losing pressure. A cylinder head leak-down test is in order, here. Not just an ordinary compression test, but a leak-down test. The shop will run compressed air into your cylinders and measure pressure losses from each one - it will tell you pretty quickly if there is a leaky head gasket.

Another test is for hydrocarbons in the coolant - if there are any HC’s in the coolant, it means that somehow exhaust gases from the engine are bubbling into the coolant - another head gasket symptom.

If the car has a turbo, have you checked any coolant lines running to that system?

I’m sure you mean oil in the coolant. Ethylene glycol is also a hydrocarbon, as are most any antifreeze liquids.

My bad, you are correct.

There are several places engine coolant can disappear to:

  • If the water pump bearing is bad, it might leak only when the pump is spinning at high speed, so you can’t see where it is coming out. Since you said you had a bad water pump, it might be a two birds with one stone case.

  • It might be forced into the overflow tank by boiling or a bad radiator cap, and ejected onto the road through the tank overflow.

  • A bad head gasket would let it into either the crankcase, the exhaust, or both. It can also cause hydrostatic lock in a cylinder.

  • A bad intake gasket could send coolant into the cylinders.

  • A bad transmission oil cooler in the radiator could put coolant in the transmission.

  • A coolant leak in the heater could be dripping out the air conditioner drip vent.

  • A leak in a rear-seat heater could be under the middle of the car.

  • I came across a strange case where a coolant line and a vacuum line were rubbing against each other until both ruptured. The vacuum line was pulling the coolant out of the coolant line.