2000 Chevy Astro Van

Not sure what to do at this point took the van on a drive to Pa last weekend went about 90 miles and the car overheated there was no fluid in the back up or radiator. Filled with fluid after it cooled my husband then changed the thermostat still overheating after high idling for 20 minutes or so. Had a mechanic flush the radiator, clean heating core and apparently it was not running hot anymore my brother in law then went to drive it home for me got about 80 miles overheated again took it to a gas station and they replaced the water pump and apparently the last mechanic did a head gasket pressure test and it was fine. Picked up car today in NJ made it 60 miles before it starting creeping up again made it home and now fluid half gone in radiator but resevoir still full. No visible leaks that we can see also heat works for a few minutes then it does not no water in oil and very little water condesation coming out of tailpipe. Any suggestions one hose is very hot the other is not coming from the radiator are they both suppose to be hot not sure what to do since there are no visible leaks not sure where the fluid is going?

 

Are your radiator fans turning on when it gets hot?

 

Do you know if anyone "burped" the system after replacing the thermostat? Could have an air pocket in the system.

 

yes the radiator fans are going on!

 

Not sure how to burp it is it something I can do?

 

With the vehicle running, take the radiator cap off. This should release any air that might be in the system.

If a mechanic did the flush, I doubt it's air in the system but it might be.

I would lean more towards a leak or bad head gasket.

If you can get the car to overheat in a autozone parking lot, they should be able to hook their scanner up to your OBDII port and see exactly what temperature the coolant is at.

It could be the engine temp sensor that is faulty causing the radiator fans to come on too late or it could be the radiator fan relay. The fans usually have two speeds, low and high. If the relay is faulty, the fans "may" be only running on low.

 

Thank you for all the info the last guy that looked at it said if was definately not the head gasket how do I know for sure do you know? We flushed again today and seems to be running a little cooler definately not overheating as quickly but the heater is still only going on for a little while and then blowing just moderate warm air out

 

You can never be sure another person is 100% right unless you do the work yourself. I hate diagnosing cooling problems, I usually replace every part. Seriously, the best way to go it to replace everything. Can be done in an afternoon if you are handy, and lasts for years longer than fixing one component, then waiting on another to fail.

Cracked radiator? Replace it.
Cracked Hoses? Replace all hoses and clamps. Clean all mating surfaces.
Cracked filler cap? Replace it.
Leaking gaskets? (head, water pump) Replace them.
Replace thermostat (check with hot water other thermostat on stovetop)

Cracked water channel? (How does your coolant look, does it have oil in it?)

If you are losing coolant, you need a blacklight, as modern coolants have a UV dye in them.

When filling up a new cooling system, I fill with 50/50 and top off. I start the car and let idle for ~15 minutes, until the car is good and warm. When the car starts getting hot, the thermostat should open. Watch the level of the coolant in your reservoir, it should drop due to the thermostat opening. Keep adding coolant to top it off. On my VW if you want to burp some out, you just squeeze a hose. When I burp it the last time, I squeeze and then cap it at the same time.

Make sure the cooling fan comes on! The car should then idle and drive without overheating with no coolant loss if everything was replaced correctly.

My 2c

 

Did any of the mechanics do a pressure test on the cooling system?

 

Astro Have A Belt Driven Fan