Overheating

[reebs]

I am trying to figure out why my car's temp gauge is also 3/4 if not closer to overheating all the time. I have the rad fan on all time as well.

I tried taking the rad cap off and watch it for bubbles. Here is my question: with the cap off should the coolant instantly start rising to the point where it overflows onto the ground? Does this mean something is blocked.

[Neu]

Alright, this is what it sounds like, you have a bubble somewhere.

Take the radiator cap off, with the engine off, fill it to the top, and the resevoir to full.

start car, with the cap off still, rev it up, up and up, the fluid should go lower a little bit, top it off quickly and put the cap back on..

[Typrus]

It starts pouring out the cap when cool?
Blocked bypass tube mebbe.
I've never seen it pour out the cap when cool.

[Petros]

if it is warm, vapor bubbles in the water jacket around the combustion chamber start to expand and forces water out, this is normal since the cap keep pressure on the water to prevent it from vaporizing the water to a much higher temp.

If it is stone cold when it does that the only likely thing that would cause that is a seriously blown head gasket, allowing combustion pressures into the water jacket.

If your system is running hot it could be either a blocked radiator, or a partially opening thermostat. Take out the thermostat and put it in a pan of water on the stove and see where it opens as the water warms up. A thermometer helps to see what temp it starts to open, but you can estimate by "feel". It should open all the way long before the water in the pan reaches boiling temp. This is the most likely cause in my experiance. I have had a heck of a time finding good thermostats, I have replaced mine 3 times in 4 years. They suddenly fail and cause it to heat up, or then they do not open all the way causing a very warm engine. The current one needs to be replaced, it opens too far and I can not get any heat in the car (and it is cold!).

If the T-stat works properly (and presuming it is not a bad head gasket) you should try flushing the radiator. If you take it out of the car there are radiator shops that can do a flow test and check the temp drop thru it.

[neonsport]

Install a new thermostat, and only use one from the Toyota dealer. It'll cost a few bucks more than aftermarket, but it'll last a lot longer. If you don't know when it was last replaced, it'll be cheap insurance.

[reebs]

I have installed a new thermostat and I still have the heat gauge almost in the red. It is starting to get warmer out and I am afraid to drive my car in fear of it overheating. The radiator was new in 2006 and seems to be fine. Could it be the water pump? I also dont get very much heat from the heater in the winter months. There doesn't seem to be any leaking coolant from the water pump.

[keith]

It could be the sending unit, it may not be overheating at all. But it could also be a water pump, radiator cap or blown head gasket. It could also be a hose that has de-laminated on the inside and is blocking coolant flow to the radiator.

[reebs]

The head gasket was replace in feb 2007 and the sending unit was replace last month.

[keith]

You could try a new radiator cap, new radiators do not come with new caps. A cap that is not holding pressure will allow and engine to run hot, especially up hill, but usually not all the way to the red.

Try starting from cold with the radiator cap off and a meat thermometer in the top tank and see what it does. Also, check the overflow tube of the radiator. I bought a new one once (AutoZone for the Tercel) and the overflow tube was not drilled out fully. The coolant couldn't get from the top tank to the overflow reservoir and back.

[takza]

I tried taking the rad cap off and watch it for bubbles. Here is my question: with the cap off should the coolant instantly start rising to the point where it overflows onto the ground? Does this mean something is blocked.

If this happens with an engine that has sat overnight...I'd say this is a definite indication of exhaust into coolant.

[reebs]

So does that mean that it could be the head gasket? If I take the cap off from being cold and start the engine the coolant will start to overflow out of where the cap was.

[splatterdog]

A bad or even small combustion leak into the cooling system will leave a distinct tailpipe smell in the radiator. Lower the coolant level giving a head space in the upper tank. Start engine, one or two good revs, shut off and give it a whiff.

Myself, I trust my nose completely but do still confirm with the blue testing fluid and combustion leak detector cause I have them.

I hope it's something simple.