Hey guys, long time listener first time caller.
The car in question - 1998 Camry 2.2. A week ago my heater hose popped out, I had to replace it, and by doing so, I allowed the air into cooling system
I replaced both upper and lower hoses, refilled it, bled it (homemade bleeding system), it was still steaming and overheating. Took it to a shop, paid 75 dollars had them bleed it, all good.
Picked up the other day today, drove around in a scorching heat daytime, the car was fine.
Hit the road at almost 10:00 p.m. at night, colder temperatures, and it started overheating again. I stopped, let it cool down and found radiator bone dry. Added a pint of coolant, made it home, cap steaming and hissing, hoses bulging. NOT overheating, though, but clearly lots of pressure in the system. I don't see any oil/coolant mixture, oil is not milky, no white smoke coming out of the tailpipe, nothing.
Few questions: Could aftermarket thermostat be causing this?
If my coolant is disappearing, where is it going - I don`t see puddle under a car, but every morning i need to add a pint or so. Is this potential head gasket problem?

 

Did you have a coolant loss prior to the heater hose coming off? When this hose came off did the coolant temp gauge go into the red zone? Red zone CAN mean blown head gasket or cracked head for this model engine!

Note sure how an aftermarket t-stat could cause a coolant loss. When bleeding the system try squeezing the two large radiator hoses to get the air out. Just adding coolant without burping the system can cause overheating issues.

Places have had known coolant leaks on this engine setup are:
Hairline cracks in plastic upper radiator tank. Check the plastic cover/shield under the engine for signs of coolant.
Rubber hoses
Heater core inside car. Check for coolant under the heater area.
Cracked coolant reservoir tank.
Blown head gasket.
Cracked head
Cracked heat at spark plug area resulting in coolant inside the spark plug area. Remove ign boots/coils to check here.
Failed o-ring seal on IAC valve. The valve is connected to the coolant system by small hoses. Seal failure can cause coolant to be drawn into the engine.

Can add an UV coolant dye and check for leaks with a black light after driving or pressuring the system. A '"block test" can be done for exhaust gases,

MAKE SURE there is no coolant in the oil as just checking the dipstick may not be enough. Draining the oil then reveals a milkshake consistency or do a coolant test on the dipstick oil,

The engine system has two issues, one is overheating and the other coolant loss. One can have a cracked head and coolant lose without over heating. A blown head gasket can cause both issues.

Might get on the issue as coolant in the exhaust will eventually cause emissions converter failure plus the exhaust emissions sensor. Coolant in oil will destroy the bearings.

 

Thanks for your reply.
I think (but I am not sure) i found the problem. The expansion tank passage was clogged and extra pressure could not be relieved. I cleaned it up, and I think this will (should?) solve the problem. All that extra pressure was building up inside of the cooling system with nowhere to go, this COULD have caused BHG?
I took spark plugs out - no smell of coolant, nothing.

 

And my radiator cap looks like this.... what is this stuff?

 

Where were you adding the coolant, to the radiator or coolant reservoir? An issue is the lost coolant as in where is it going.

Given the debris on the cap and plugged reservoir tank consider flushing out the coolant system. Don't use cleaning chemicals as this can remove too much debris and clog up the radiator!!!!! Just use water from a garden hose or such. A plugged radiator can cause all kinds of issue including over heating.