lluahs

My 92 es300 has a random bubbling coolant reservoir. i cant figure out what it is, it did it today on a 20 minute drive with the ac on. i just drove 1200 miles earlier in the week without the issue. So here is what been replaced in the last 5,000 miles:
Front headgasket
Thermostat
Waterpump
Both coolant caps
Timing belt

Some things to note: the car came with an after market radiator and im not sure the new cap is for that radiator, although it seems to fit. There is no evidence of burning antifreeze coming out the exhaust pipe. the temp gauge never goes past the half way mark.

Any help is greatly appreciated

Bdub215

iTrader: (1)

bubbling in the coolant reservoir is sign that the HG is on its way out. Combustion gases are mixing with coolant. granted my car did this for 5-6 years and didnt miss a beat. however mine eventually did go. Did you not do both heads when you had the motor apart?

KLF

Sounds like a head gasket to me. Try to do a leak-down test to confirm.

EEngineer

your head gasket is ****ed. sorry, time for a new motor or an big overhaul job

lluahs

I really don't think its the hg...it could be but all signs do not point to hg. everytime its done this, it was city driving, it never did it hwy driving 1200 miles. plus i don't see white smoke out the exhaust or exhaust out the reservoir. im more inclined to think its the radiator. Thanks for ur replies, ill keep the hg as a real possibility.

tjmhillz

iTrader: (6)

Does the coolant in your over flow tank look like chocolate milk if so then its a blown hg. When the wp and therm was changed was the system bled?

lluahs

Oil looks good and Toyota antifreeze looks great

randal

That the coolant does not boil over on highway trips makes me think it is either the fan or radiator. The main diff is the city driving does not put as much airflow thru the radiator. If the fan appears to be working at high speed when hot then the rad is definitely a big suspect. If the fan is spinning slowly then that crazy power steering fluid design is in need of repair. good luck with that.

PFB

A defective radiator cap or the wrong radiator cap can also cause your symptoms, as it will allow your coolant to boil at lower temperatures.

Before you panic about the head gaske being bad, get a New cap from Lexus, and see what happens.

Phil

lluahs

Ok so i found some terminal connections to make the radiator fan spin at full blast(e1 to op1). My fan still spins slow, so slow i can stop it with my hand. so i believe the issue is with the fan not kicking on high. im not sure what would cause this, time to research. please point me in the right direction if u know how

PFB

You're saying that your car is running at normal temperatures, yet you get bubbles in the reservoir. This symptom does not indicate a problem with the fans.

Unless your HG is gone, I still think that you should first change your radiator cap back to an original Lexus cap, not an aftermarket cap, it's a cheap 1 minutes solution, and may just fix all of your problems.

If that does not work, you can than go on to do further diagnostics.

Phil

lluahs

The radiator is aftermarket...so lexus cap wouldnt fit ...interesting post, very similar to my troubles:
http://us.lexusownersclub.com/forums/topic/30943-hydraulic-cooling-fan-and-overheating-problems/

lluahs

It always reads normal temps, which could be a bad sensor, vie replaced the temp sensor on the drivers side...no difference...plus would i get a code if it went bad? the fan seems like the culprit atm

LeX2K

Why did you only replace the front HG? Your car actually has two coolant caps (assuming the radiator is anything like the original) so replace them both. After you replace the caps, bleed any air out of the cooling system using a spill proof funnel, better if you park the car on a incline.

Make sure your power steering system is working properly, clean fluid with no leaks and the correct level. The cooling fan is run off of the power steering system it is not electric.

randal

There is a cooling fan ECU located behind the glovebox. You can pull the connector on that and make some checks with a volt-ohm meter (you do have one of those? ;-) If not, maybe you can borrow one?

Looking at the attached drawing and chart, make sure the solenoid(pins 2 & 3) reads around 8 ohms when the engine is cold. Then check the thermostat sensor(pins 9 & 10) when the engine is hot to see if it is around the 1500 ohms.

Report back to Gestapo central with your findings.