Changed coolant/thermostat now van is overheating.

Changed coolant/thermostat now van is overheating.

Postby VanGoBOOM [OP] » January 16th 2012, 2:22am

Hi all. New to this forum and I'm happy to be here! I have a 1998 Astro LT with 99K miles (only 600 to go to 100k!)

About a week ago I changed the coolant on my Astro. Drained, backflushed, then cooling system cleaner and then another flush and new thermostat. Thats where my problems started.

The coolant temperature sensor went bad after that(or so the OBDII/ECU reader says) and the van would take forever to reach operating temperature but once it did it just stayed there (around 160°). The heater blew lukewarm air and sometimes would blow cold air.

Changed the sensor, cleared the ECU and started her up. It got to the red line on the temperature gauge really quick (260°) and stayed there.I turned her off, let her cool down and then started again a couple of times until the thermostat finally opened up but the temperature was still between 210°(half way) and full red (260°) and the heater blew really hot air.

I let it cool for a few hours then took it for a spin. The temperature got up to midway and redline and stayed there. It once got below the half way point but it was always between the red line and the half way mark.

I'm thinking its the water pump but I cant be sure just wondering if any of you guys have run into this problem before and maybe post some pointers or tips to find out whats wrong.
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Re: Changed coolant/thermostat now van is overheating.

Postby Big_kid » January 17th 2012, 1:55am

Welcome aboard!

Is it possible your thermostat is sticking?

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Re: Changed coolant/thermostat now van is overheating.

Postby unrreal » January 17th 2012, 2:31am

it could be two things, you either have a bad t-stat or you have air in the system, i ran into this problem also with my 99 i got a new t-stat that ended up being bad after i replaced it it was still overheating, i ended up having air in the system, you have to park your van at an incline front higher than rear open the rad cap turn on engine and rock the bumper up and down until the rad burps the air out, it may take a couple of tries to get all that air out of there so good luck... :D
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Re: Changed coolant/thermostat now van is overheating.

Postby paintdrying » January 17th 2012, 1:40pm

Did you buy the thero stat at autozone?
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Re: Changed coolant/thermostat now van is overheating.

Postby Phantom » January 17th 2012, 3:40pm

You may have bought a bad T-stat , it happens , be sure to use a good quality brand , if you suspect that the pump is weak you can take van to radiator shop and tell them you want to check for leaks and would like a pressure test , they usually do it for no charge , , it should make about 15-16 lbs of pressure and hold it , , when filling rad after draining I jack up the passenger side front of van run engine till it fully warmed up then gradually pour coolant till it is full , since it takes a few seconds or a minute for coolant to fill rad passages it may take a few minutes to complete the task .
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Re: Changed coolant/thermostat now van is overheating.

Postby frank12006 » January 17th 2012, 6:25pm

paintdrying wrote:Did you buy the thero stat at autozone?

I just changed my t-stat, i purchased at autozone. are these not as good as other parts retailers. my van has been running a lil hotter since then.
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Re: Changed coolant/thermostat now van is overheating.

Postby maximus7001 » January 18th 2012, 9:40am

I went through the problem of cheapo bad stats right out of the box on more than 1 car over the years. When this happened on my Safari I was lucky it did not blow a head gasket. Went to the GM dealer and got one of theirs and it works great.
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Re: Changed coolant/thermostat now van is overheating.

Postby Bigblaine301 » January 18th 2012, 1:07pm

2 answers, first faulty t stat. But for sure I think air trapped!
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Re: Changed coolant/thermostat now van is overheating.

Postby VanGoBOOM [OP] » January 19th 2012, 8:12am

Thanks for the help guys I think its the thermostats I bought that are faulty.

Bought both at autozone, one Failsafe brand and another Duralast. The one to fail and overheat the van into the red zone was the Failsafe. (Ironic cause its supposed to stick open in the event of real bad over heating.) Took it out and bought a more expensive Duralast stat.

The Duralast wouldnt open until it was about 220°, would sometimes get stuck closed and make the van over heat into the red zone. I decided to test it out and put it on the stove with boiling water. It didnt open until the water was at a rapid boil and when I cooled it down and it was stuck open! Manually closed it test it again and this time it didnt open at all. I cant believe autozone would sell junk like this! The stat has a lifetime warranty but I dont know if I wanna keep switching thermostats until I finally get a good one. Probably just gonna hit up the dealer tomorow and get an oem stat.

Also I ran the van without a thermostat just to be sure it wasnt something else and it was fine. Ran cold but at least it didnt overheat and at least I know coolant is flowing freely through the system.

Once again thanks everyone and hopefully tommorow i'll get this fixed! :wave:
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Re: Changed coolant/thermostat now van is overheating.

Postby Phantom » January 19th 2012, 2:26pm

Stant brand T-stats have always been reliable for me ,,
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Re: Changed coolant/thermostat now van is overheating.

Postby paulo57509 » January 19th 2012, 4:25pm

When you re-fill the cooling system, leave the radiator cap off, run the engine and allow the thermostat to open a few times; looking into the radiator, you'll be able to see the coolant flowing through the tubes when the thermostat opens.....wear safety glasses just in case. This will burp the air out of the system.

While waiting for the thermostat to open, continue to top off the radiator. After the thermostat opens a few times (you'll lose some coolant out the filler) top it off one last time and install the cap.

Don't forget to fill the overflow tank.
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Re: Changed coolant/thermostat now van is overheating.

Postby RECox286 » January 19th 2012, 5:20pm

Stant is the only brand on the shelf in my stable. Not to be funny, or egoistic, but, stick with what works.

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Re: Changed coolant/thermostat now van is overheating.

Postby Shad0wXCalibur » January 19th 2012, 5:22pm

Unless it looked corroded, I would have left the factory thermostat in there. I had an issue just like that with a Chevy Cavalier we had once. The best way to get air out of the system is to drill a small hole in the thermostat. I think I went with a 3/32 bit but go even smaller if you live in a really cold climate or it takes a while to warm up. Works really great. I took out the factory thermostat in my 2000 while I was changing the coolant, cleaned it up real good, drilled a hole and put it back in. I bought a Duralast stat for my 87 while I had the whole front of the engine taken off and drilled a hole in it too with no problems. I think I replaced the original 25 year old stat in that thing. It was a little rusty and still worked though!

Oh yea. Don't get failsafe stats. There's reports all over the web of them stuck open permanently (fail-safe mode) even though the engine wasn't overheating causing an engine to be over-cooled or take too long to warm up.
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Re: Changed coolant/thermostat now van is overheating.

Postby FLSafari » January 19th 2012, 7:49pm

My 5 cents on getting air out of the system. When you fill the system with coolant and run the engine, always ensure that the heater is turned to FULL ON. That ensures that coolant is flowing through the heater system. Leaving the rad cap off will help with the burping but be careful of the hot temperature of the water.
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Re: Changed coolant/thermostat now van is overheating.

Postby smokinjoe » February 10th 2012, 7:03am

Wow thats strange. I have changed my coolant a bunch of times & never did the high front end thing. I was careful to get air out but when I ran it w/o the rad cap it would start to overflow when it got hot with no pressure so I figured it was full. Years of no issues. Guess I was lucky.
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Re: Changed coolant/thermostat now van is overheating.

Postby acgcarpentry » November 3rd 2012, 1:44pm

I am havibng this same exact issue with my 02 astro van right now, been going on 3 days of messing with coolant and having none and have to drive 45-1hr away and have to keep filling it for some reason,
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Re: Changed coolant/thermostat now van is overheating.

Postby chevymaher » November 3rd 2012, 1:54pm

When is it losing coolant? Driving. Do you see puddles parked? How low is it when you add? Can you smell it? Oil looking good? More info please.

It could be as simple as a bad radiator cap. Or a leak. Or a intake issue.
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Re: Changed coolant/thermostat now van is overheating.

Postby RECox286 » November 3rd 2012, 3:26pm

Check the oil dipstick for milkshake...

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Re: Changed coolant/thermostat now van is overheating.

Postby edlps » November 3rd 2012, 4:07pm

I replaced thermostat and drained/cleaned the cooling system a number of years ago and afterward my system was slowly getting hotter and hotter over time and was red-lining a few times which never happened before, i checked thermostat it was fine i figured rad problem, popped it out took it to rad shop, had it cleaned, 80-90% plugged, guy said probably caused from draining the whole system, youll get lots of rusty bits from the block stirred up and into the rad. Problem was fixed.

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