What are the causes?

Local tech school thought we need to fix leaks (there were two leaks water pump and thermostat gasket) so they replaced water pump with timing components (because they were there) ...

I took it to school because it had the same issue..now issue is still there but now its little better in that...it takes little more time for the car to overflow..

radiator fan does come on ...

School instructor think that its head gasket break that opens up at high temperature and that is causing this overflow ...which is beyond my understanding ...can someone explain the connection?

What else could be reason?

 

If the head gasket is bad, pressure from the combustion chamber will leak past the gasket and into the cooling system. Not very likely as head gaskets these days are steel and it would require two breaks, one around the cylinder, and another around a coolant passage. You would probably be seeing white smoke on start-up. Anyway, cylinder head leaks are properly diagnosed with a compression test.

Go back and re-read what I wrote earlier about when the fans should come on.

 

I suggest that you get a coolant pressure tester. Both Autozone and Advance Auto will loan you one. That will tell you if you have a leak, a blockage or a bad head gasket.

John

 

In earlier thread I said fan does not come on..but it was my mistake...Radiator fan does come on ...so what is the best way to rule out thermostat ...if thermostat is partially blocked it wont let hot coolant go to radiator (in this case lower radiator hose) so what can happen to this coolant which is not passed to radiator...it will stay inside the engine and circulate and eventually overflow from overflow tank?
My understanding is ...only way to for coolant to go to over flow tank is to through radiator ...correct me if I am wrong..

Also I left the car at local technical college for them to fix and they replaced water pump ...and timing components and thermostat gasket..and they said thermostat is fine..(I am not sure if they checked it) I also asked if radiator is clogged or hoses ...they said no radiator is fine as well.

I dont trust them any more...how do I check thermostat ...radiator and hoses (without removing anything from car) if they are ok?

 

Your car has a bypass hose so coolant will circulate when the thermostat is closed. I don't think that's your problem.

John

 

Also, you said earlier that the car was not overheating. If the thermostat was not opening, chances are it would be overheating. If it was not closing, it would take a long time to warm up. Thermostats are tested by taking them out and heating them up in a pan of water on the stove. If you have a candy thermometer, you can see the temperature at which they open.
Removal of the thermostat on your car is a PITA requiring removal of the alternator. If you're going to go through all the trouble of removing it to test it, you might as well just replace it.

 

Well I could be wrong ..when I said car is not overheating ...I meant the temp gauge does not go all the way to red but actually speaking when it reaches to middle on the gauge ..it starts spiting out coolant and smoke under the hood so I have to turn off engine so I would say it is overheating..
when I gave to tech school they changed thermostat gasket but even though I insisted they did not change thermostat ...said...its ok...in other thread you explained how this car cooling movement is bit different than others which makes sense..

 

If the temp gauge is only halfway then your car is not spitting out coolant because it's overheating. It either has a blockage or a bad head gasket. As I mentioned before you need to put a pressure tester on to see where the problem is.

John

 

Where exactly is the spitting and steam (not smoke) coming from? There's your leak.

 

It was not leak(tech school fixed that) ...it was spiting was from recovery tank

But something happened amazingly...

Last evening I decided to check further with temp gun ..

car took long time like more than 30 mins at idle to get to operating temp

and no coolant spit form tank or any where else...yes I could hear and see coolant bubbling inside tank but it did not come out like before...

(yes there was enough coolant ...in between min. and max mark)

Both fans came at about 230 F ...

Can someone explain about fan...I thought one fan comes on first ..its called low fan which comes on at about 219 and high fan comes on at about 235?

but in this case both fans came on at about 230 temp at upper radiator hose

Once the fan came on ...it lowered the temp so coolant did not spit out at all...which is a good thing...

Further...I did check with combustion leak testers thrice and no combustion gas were present in the tank ...can I say no head gasket problem or cracked head ?