How do you bleed air from cooling system?
 

I just drained and filled my engine cooling system with Toyota Super Long Life Coolant (Pink). However, when I turn on the car, I can hear some water traveling in the engine compartment (probably coolant) right before the internal combustion engine kicks in. It sort of sounds like water draining in a pipe behind a wall when someone flushes their toilet upstairs while you're downstairs.

I'm thinking it is trapped air. How do you bleed this? I tried running the car with the heater on (highest temp with low blow) with the radiator cap off. I ran the car like this for 10 minutes but coolant kept on flowing out.

How do you bleed the trapped air after you drained and filled your engine cooling system?

Also, how do you change the inverter coolant?

Thanks in advance.

Re: How do you bleed air from cooling system?
 

NEVER fix something that isn't BROKE..!!

Take it to shop that knows what they're doing, an air bubble, "vapor lock", in the inverter cooling circuit can get COSTLY.

Re: How do you bleed air from cooling system?
 

I haven't changed the inverter coolant yet. I was just servicing the engine cooling system. This system is the same as the ones on any other cars. My car was approaching the 100,000 mile mark and that was why I was draining and filling my engine cooling system.

Re: How do you bleed air from cooling system?
 

The service manual states the following:


coolant.

If the coolant level is low, add coolant.
(e) Install the radiator cap sub-assembly and reservoir

tank cap.

I don't know if this information will help but it's worth a try. I thought there was a plug at the top of the engine for bleeding the air but apparently there isn't.

Also according to the service manual page HV-325 it appears that the coolant for the inverter cooling sytem is connected to the radiator via a small hose near the top. See the attached pdf file. I would assume that draining the radiator would also drain the inverter. Maybe there is air in that portion of the system. Try removing the inverter coolant cover before pressing on the hoses. I hope this information helps you.

Re: How do you bleed air from cooling system?
 

Also set the heater control to full hot. That should get the remaining air out of the system while burping the hoses.

Re: How do you bleed air from cooling system?
 

Based on the diagram, I think you are right about the inverter coolant. However, I'm 100% sure that draining the engine cooling system does not drain the inverter coolant because my inverter coolant reservoir did not drop, before or after I did the drain and fill.

I'm currently looking at Toyota Service Manual for a 2008 Camry Hybrid (I have access to one at work.). I essentially filled the engine cooling system the way the manual recommended, which is verbatim to what you typed out. So I'm not too worried at this point because my engine isn't overheating, and the water noise is starting to go away.

According to some of the mechanics that work in a different department from me (I'm an engineer at the Cal EPA), those coolant air pockets will eventually bleed itself out. They told me to just watch the engine temperature gauge and reservoir coolant level.

Those guys did mention some methods on how to bleed air pockets, but they were a little too invasive in my opinion.

I'm still reading the manual (5 volumes) to look for other troubleshooting methods, as well as how to change the inverter coolant. I'll let you guys know what I did and what happened so that we can learn from each other.

Thanks for all your help.

Re: How do you bleed air from cooling system?
 

That's my preferred way to bleed air pockets from the cooling system. I tried this once already. Maybe I need to try it a couple more times.

Thanks for the recommendation.

Re: How do you bleed air from cooling system?
 

Inverter and ICE coolant circuits are separate - the ICE loop runs a lot hotter than the inverter does normally. The inverter coolant has its (electric) pump and a separate heat exchanger, along with the separate reservoir. Although the inverter heat exchanger is located in front of the ICE radiator, the two don't mix fluids.

Re: How do you bleed air from cooling system?
 

FYI, the air pockets eventually bled itself out of the cooling system. It took about 4 hot/cold cycles, which was about 2 days for me. I never had any overheating problem during this entire period, and I was driving for 40 miles highway stretches. My recommendation is to watch the temperature gauge (note where it is normally--a little under the half mark) and refill the coolant reservoir if and when it drops (I usually check before cold starting the car). Thanks for everyone's help.

As for the inverter coolant, there is a separate drain and fill procedure listed in one of the 3 or 5 volumes of repair manual for the Camry Hybrid. I haven't changed my inverter coolant (Uses the pink Toyota Super Long Life Coolant) yet, but I will do so within the next 6 months.