Mystery Coolant Loss (4 Viewers)

[ADP91]

Hi everyone,

I've had my 1997 Lx450 (280,000 km) for about 9 months now and over the last 3 months or so its developed a coolant loss that I can't trace. I'll top up the radiator and the overflow tank to the max fill line and after driving for a few hours and letting it cool completely I'm down about 2cm in the overflow tank.

I've done the following diagnostics:

• Looked for visible leaks and tightened all coolant hose clamps. Even did a UV dye test in the radiator and no visible leaks.
• Combustion leak tester (came back negative after three tests)

Other notes:

• Engine is running fine, no misfiring, no white smoke on start up, engine temperatures are rock steady in all driving conditions.
• Oil is clean, but there is some white-ish residue on the inside of the oil fill cap. But I live in the city so my guess is this is due to condensation build up from shorter trips.
• Transmission fluid looks clean.
• No leaks inside the cabin from what I can see and no sweet coolant smell either.

Any suggestions for how I can diagnose this? My next steps are doing a cooling system pressure test and then a cylinder leak down test.

Any advice is appreciated!

 

[77mustard40]

Can you take a look at the overflow tank after getting the motor up to temp to see if the tank is overfilling while hot and overflowing? It could be as simple as needing a few new radiator cap.

I experienced the same issue in the overflow tank a couple of years ago and it was actually the HG starting to fail. Have you pressurized the coolant system to see if it holds pressure?

 

[Mag71k5]

I couldn't find my coolant leak for the life of me. Headgasket blew out on cyl 3/6. If nothing else works, check under the exhaust manifold.

It never hit the ground until it got way worse one day.

In my case, looks like the PO i bought it from tossed some block seal in and I happened to be the next victim. Lol.