LexusMech

Hey Guys,
I've been dealing with air getting into the coolant system for a while now and know about nearly all available options to diagnose this issue. Narrowing it down has been difficult to say the least

Car
Lexus ES330 2005

Problem:
Gurgling & Whooshing sound behind the dashboard. Occasional overheat. There's a steady amount of small bubbles that come through the spill-free Lisle funnel when trying to bleed the system of air (front end lifted on rhino ramps) Heater HOT, fans high.

You'd think this would be a head gasket issue, but the head gasket was recently replaced by a reputable shop - all spark plugs were changed out as well.
No external leaks seen with UV dye
No dampness/wetness by passenger side that would suggest a heater core issue

What I've done:
Replaced thermostat with OEM Toyota thermostat
Replaced radiator cap with OEM Toyota cap
Replaced radiator with an Oreilly's aftermarket (was the cause at a prior time)
Block tester 5-6 times confirming no combustion bubbles is getting into the system, (also tested by muffler to see if fluid was good as well)
Pressure tested 15-17 PSI cap and system, nothing looks suspiciously off.

The radiator was replaced and everything was fine for a year then the dreaded air came back into the system with overheating issues.

One thing I noticed during an air bleed (with the yellow Lisle funnel) was that the small bubbles pretty consistently flowed through. So I tried something different. I'd squeeze the upper rad. hose and small/medium bubbles always seem to enter. I stopped the engine continue to squeeze the upper rad hose until no bubbles came through. at this point the thermostat is likely shut but as soon as I turn on the engine, the bubbles start coming back right away.

I'm thinking there's some breakdown in the seals around the water pump or hoses.

any useful suggestions?

LeX2K

Assuming you do not have a HG problem* air entering the cooling system can happen on engine cool down. As the system cools the coolant contracts, to get around this the overflow bottle and radiator cap work in tandem to allow coolant to be drawn back into the radiator. If there are any leaks in the system air can be drawn in, the leak can be so small you won't see it or coolant may not leak out at all but air can still be sucked in.

I would pressure test the system, if that doesn't show anything spike the coolant with dye.

*block testers do not always show a positive result even when there is a HG failure I've seen this happen. Also a cracked cylinder head can cause your symptoms were the heads tested for cracks?

LexusMech

Can't really assume anything at this point - could be HG again. Heads have not been tested for cracking/warpage.

Is there any way to find these tiny leaks that aren't related to the heads?

The PSI of the system settles at 13 PSI after 20+ minutes. I know 17.1 PSI is the limit for the es330.
No leaks can be seen with UV dye, I've got a strong blacklight that doesn't show anything.

nsghtbrwry

Since the system is pressurized, wouldn't you only see bubbling when the engine's on if you have a BHG? I mean, any opening would be pushing coolant out, not sucking air in, right?

EDIT: I second pressure-testing the system. If you can't find anything with UV dye - and let's assume that your heater core is good because you don't smell coolant in the cabin - the leaking pressure would indicate a leaky HG

LeX2K

On engine cool down air can and will get sucked into the system if there are any leaks, or if the head(s) are cracked. If you keep hearing rushing/gurgling noises then this is what's happening, and I can't stress this enough you may not have any visible leaks but air can still be sucked in.

Saveth

I'll chime in since everyone else has a 1uz. When I did my timing belt and water pumpfor my 3uz, I bled the system with the rad cap off like others. My coolant level hasn't move one bit.