1996 Camry V6 overheating

[McBrowntrout]

Hi all,

Scoured the threads, but couldn't find specifically what I was after, so...
My 1996 Camry Vienta V6 is overheating (less than 120K)- here's a bit of the history: The old rad cracked along the top and the car overheated, so i replaced the rad with a re-condiditoned one from Natrad (fairly reliable co.). The problem persisted, so I changed the thermostat. The problem is still persisting, and here are the current symptoms: Car will hold a steady temp. whilst driving (city & highway), but all of a sudden the temp. will spike up to the red, and coolant blows out of the overflow tank. When I turn on the heater to help, the temp comes down, but then hot air stops coming out of the vents, and the temp. rises again. This hot air on/off is intermitent. Also, the idle becomes a bit rough after about 5-10 minutes. I suspect that the head gasket is gone, allowing exhaust into the cooling system, but I would like to draw on the vast experience here to see if there is anything else I should trouble-shoot prior to ripping the heads off.

I have pressure tested the cooling system and it holds 100Kpa with no visible leaks, no worries. I have just read that the thermostat should be installed with the wee pin thing in-line with the top housing stud - something I didn't pay attention to, but will re-align tonight. The top and bottom cooling hoses feel the same temp (i.e. both are hot) when the engine is up to temp (suggesting it's not the pump?). I also plan on getting some test blocks to run in the rad to see if any exhaust gasses are in the coolant. Aside from this, any other suggestions? I have a fair amount of mechanical experience, and could change the HG's myself, but would hate to go through it all and find that the problem was elsewhere all along. Any suggestions? It's a great car, and I would really lament having to get rid of it.

Cheers,
McBrowntrout (p.s. sorry for the length of the post......!!!!)

[McBrowntrout]

Thanks pgmomni,

I was thinking H2O pump as well, but the rough idle after it warms up had me uncertain (suggesting a tiny HG leaks / crack that only opens fully when it expands with heat?!?). I'm not sure how / if the WP not working properly would affect the idle. In any case, I'll perform the tests I mentioned in the original post, and go from there. I may end up changing the HG's and WP at the same time if I'm going to be doing all that work on one or the other anyway. I guess I'm just in that wishful thinking mode where I still hope it's something easy like a sensor...... Still iopen to any more trouble-shooting suggestions before I go the whole hog and rip it all apart.

Thanks for the heads-up as well regarding the model name. I was unaware that the USA Camry was not badged as a "Vienta" and have edited the post title accordingly. Hopefully more folks will respond now.

Thanks again,
McB

[carsrus]

If your going to remove the thermostat again replace it, they do come bad new. To me it seems as id one of the head gaskets gone or a cracked head. If the timing belts never been done you might as well give a shot at the waterpump before tearing it completely down.