My darn toy is having some over heating issues, but it's not consistent. Last summer the radiator starting leaking, and I always kept it topped up. So I pulled the radiator out and had it fixed. I put it back together and starting using it again this year, and this is where the trouble begins.

The car runs great all the time and will start right up. The plugs look great, the timing is where it should be, idles perfect, you can see the flow of coolant through the radiator from the top. You can take off in the car and drive for 4 hours and it won't do one thing. High way, city, 95 degrees not a problem. Then drive it the next day at 75 degrees and it'll start steaming and foaming. Looks like someone put bubblebath in the radiator. And these bubbles will shoot several feet in the air. Once it's done with this episode, I can top it off and it'll be fine for hours again. Then I can stop for 10 minutes and hop back in and within 5 minutes it'll do it again. Or I might take off fresh another day and it'll do it within 5 minutes. Or not.

I'm alittle stumped. The bubbles confuse me the most, because it really looks like I've got a team of bubble blowers under the hood. None of the plugs appear to have been burning antifreeze, I have no white smoke, no oil contamination. I don't have any coolant leaks either. I don't have to add any water unless it has a steamy bubble fit. Any ideas on this one? Thanks!

Before this I had always ran 50/50 green antifreeze in it with no issue, which isn't always recommended in a non pressurized. So I have tried it with straight up water too, same problem within the same time frame.

Have you had the cooling system flushed? Not just to clear out the old coolant but whith an acid to remove any scale and build up.

I caught it at the start of one of it's bubble fits...if you put your hand to seal up the top of the radiator so only the overflow tube is open, you can feel the pulse of air come out as the engine is running. Blown head gasket.