5SFE bubbles still in overflow tank after head gasket replaced

[Circlotron]

One of the cars in our family is a 99 Camry with a 5SFE engine. Had it for about 10 years, currently 184,000km. As the title says, we did the head gasket because there were bubbles appearing in the radiator overflow tank. Slightly more than one per second when idling. The engine ran just fine though. Now it is all back together and there are still bubbles appearing. What else could cause this? A cracked block? Radiator cap allowing air to enter as it cools down? Engine has never been overheated and is only driven very mildly.

[lefty o]

could still be the head gasket if surfaces arent flat, could be a cracked head or block.

[miniv8]

EGR cooler?

[BillK]

Did you have the head resurfaced ? Almost every aluminum head I see needs resurfacing. Most are fairly straight but there is almost always some indentations around the bore diameter where the gasket fire ring has been digging in and moving around. 99% of the time I can see exactly where the gasket was leaking and there is always some gouging there.

If you did have the head surfaced how about the deck ? How did it look.

[prairiehotrodder]

Before you did the head gasket did you pressure up the system and confirm coolant was leaking ? Just seeing bubbles isn't a good enough reason to do head gaskets. You need a few pieces of evidence.

[Walter R. Malik]

I once bought this Chevrolet "Bow-Tie" block for a road race engine. After about 20 miles of hard racing it would spill the water from the cooling system and overheat ... couldn't finish the race. No bubbles in the cooling system at low cylinder pressures at idle and free running ... only at Wide Open Throttle racing with high cylinder pressures for an extended period of time.
We checked heads and gaskets and everything we could think of ... tried racing it again & again when nothing seemed to be going wrong; then it would happen. After a few tries, changing the block solved the problem.

Well, to shorten this story ... water was not escaping or leaking anywhere until this bizarre happening. A year later we found that combustion pressure was getting into the cooling system right through the block casting. Combustion pressure is much higher that water pressure so, water would never leak ... having the block impregnated solved the issue.

This problem would have never even shown itself in a drag race only engine as it took a while of hard racing for it to show itself.

[Racer71]

Those were known for pulling head bolt threads in block if memory serves me. Same thread as North Star caddy as I used my time sert kit on a few yotas with head gasket issues

[Kevin Johnson]

Just a suggestion to use a kit that tests the coolant for combustion gases (the fluid changes color when present). There are other great ideas here.

[Circlotron]

An update on the original post. Replaced the radiator cap and all seems well for the past few months. Looks like the perished rubber seal was allowing some air to be drawn back into the system when cooling. So it must have been both a bad head gasket and a bad radiator cap. After a 1 hour 100km / 60 mile drive with the old head gasket you could still see the bubbles in the overflow tank. New head gasket and old rad cap and it was still bubbling after a short drive. Couldn't try a long drive because here in Melbourne Australia we have been in lockdown longer than anywhere else in the world apparently. Anyway, new cap stopped the bubbling after several hot / cold cycles.

[Racer71]

Good deal and thanks for update, so many topics go un updated on message boards