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1998 Avalon with coolant leak

I have a 1998 Toyota Avalon with a coolant system leak and I just replaced the upper and lower radiator hoses. The car continues to leak or burn coolant but I cannot find any trace of the leaking under the car. I filled the coolant and ran it for a day no problem but after that it seems to not want to hold coolant. There was none left in the reserve bottle last I checked the morning after filling it but with normal driving the engine doesnt overheat. What could the leak be? And if it is a possibility of the head gasket could I put some sealant in to stop the leak?

I suggest using a coolant pressure tester to look for that leak

Another thing I would do is to take a look at your coolant . . . if it looks like coffee, you know that the oil and coolant have mixed, possibly due to a bad head gasket

Measure coolant added over several days and report back.

Don’t add any stop leak until you are sure of a leak.
@db4690 is right about checking the coolant and the oil if either looks odd, you have a leak.

You also may have just had air remaining in the system. It may have taken a couple or cycles of getting it to operating temp, to get the air out.
Not including what you first filled it with, how much extra coolant have you added.


I believe on this year there is a coolant hose under the intake plenum. It is common to leak or burst. If it only has a small leak the coolant will evaporate from the heat of the engine. Use a pressure tester on the system and you should be able to see it. Other common leaks were along the radiator tank, water pump, head gaskets and the radiator caps were also known for failure.

Find the leak with a pressure test. Mine leaked at a crack in the top radiator, where the hose attaches. This was caused by worn engine mounts allowing the engine to rock, cracking the plastic radiator tank. Fix included a new radiator and engine mounts.

I saw a major drop after the car was just sitting on the driveway unused over night right after having the coolant filled with a coolant fill machine. and regarding the hose behind the intake plenum i will check on that because i never realized to check it. but i do believe the engine mounts are in good shape but i will have my mechanic run a leak test on the system.

I think the 2 lines on the intake go to the heater core.

Mine, same generation, had a leak due to a crack in the (Plastic) radiator.
Very hard to see.

The hose I am describing sits under the lower intake manifold and runs side to side on the engine.


My 2005 Camry has the same 1MZ-FE engine, and it also still has that hose

If you have a mirror and flashlight look at the hose carefully for any swelling. They seem to break at the worst time, learned that the hard way on my old camary.

@melott‌ i checked and the car is with my mechanic but the radiator seems to be fine and the coolant level doesn’t seem to have decreased at all so it seems ok

A UV sensitive dye can help find sneaky leaks too. A kit will run you about $50 at any parts store. It’ll make the leak path light up like an early '70s house party.

A pressure leakdown test is in order if you still can’t find it.