I have an 88 4Runner with a 3.0 V6. I replaced the head gasket a while back and while was doing that I replaced the water pump and thermostat. Now that summer is here, almost every time I take it out the reservoir is bubbling when I get back and stop the truck. Granted it is pretty hot outside....about 100, but the temp gauge says it is below the halfway mark. The temp sensor is new so I know it isn't that. To try to fix this I have:

Replaced the radiator cap
Flushed the system
New water pump
New thermostat
Looked for milky oil - Nothing
Checked the coolant for exhaust residue - Nothing

Has anyone ever had this problem? I want to say it is the cap still, because the engine isn't hot on the gauge or when you open the hood. It feels normal. The little lip was a little corroded when I put the new cap on the radiator and the spring doesn't really compress when you put the cap on.

Has anyone had a problem like this before?

 

My bronco did this one day. Try going down to schucks/oreillys and getting a product called "water wetter", made my camaro run 20 degrees cooler, same with my bronco

 

Peow - that is funny you said that, I actually just put some of that Red Line Wetter Water in last week and it looks to run cooler on the gauge, but it still did the bubbling in the reservoir today and yesterday.

 

is it only bubbling in the reservoir? I believe someone else solved this problem with replacing a faulty radiator cap.

 

interesting. next guess would be that your reservoir is too full. when water gets hot it expands, causing the bubbling.

 

I changed the cap and it doesn't have too much coolant. I put it at the cold level when it is cold and when i get back to the house it is full and bubbling over.

 

maybe pull even more out? as long as you actually have coolant in your system, then you shouldnt worry. also, as long as the temperature isnt pegged at 250, either.

 

Just because you're not getting oil in the coolant and/or coolant in the oil doesn't necessarily mean you're not losing compression to the water jacket. Have you done a compression check since the headgasket replacement? The coolant will NOT boil under normal circumstances, whether it's 100+ degrees or not.

 

I'm afraid bubbles in the reservoir usually means a HG issue still.

 

The first symptom of my failed HG was bubbling in the coolant lines, followed by white smoke out the tail pipe and disappearing coolant. Never had a milkshake.

 

Fellas, I had shop check everything out and it was the radiator!! I am very excited about that. The lip was bad on the neck and it was full of junk. It was the original. The shop did a leak down test and another test where they check for exhaust in the coolant. I didn't have the equipment for either of these, so I took it to the shop. It only cost $35 for the test and $165 for a new radiator.
I put it in 2 nights ago and it changed everything. I drove it around all day yesterday and it worked perfect. No bubbles no leaks. I am very relieved!! After doing all of that work on it, I was starting to second guess everything.

 

which radiator did you end up buying? aluminum, brass? im about to buy one to replace the original +300,000mi on it. various cooling issues finally worked out just need a new rad.