Why does my thermostat keep breaking when I drain my coolant?
 

The last 2 times in a row that I have drained, refilled, and attempted to bleed my coolant, the thermostat has been stuck closed (broken).

Why does this keep happening?

My only theory is that perhaps I'm draining the coolant while the car is 'too warm' and thus the thermostat undergoes thermal shock. Is this possible?

0a

Re: Why does my thermostat keep breaking when I drain my coolant? (Achenar)
 

is it an oem or aftermarket unit?

Re: Why does my thermostat keep breaking when I drain my coolant? (Rodney)
 

The first one, I'm not sure. It's a second-hand motor. The second one was from Pep Boys, and has operated fine for the last 3 years (until I drained my coolant).

-Matt


Modified by Achenar at 8:10 AM 2/1/2007

Re: Why does my thermostat keep breaking when I drain my coolant? (Achenar)
 

ditch the pep boys one and buy an oem. i just went 195,600 miles on an oem one, and it stuck open. i would guess that i drained the coolant prob half a dozen times, if not more during that period. OEM https://honda-tech.com/forums/images...es/emsmile.gif https://honda-tech.com/forums/images/smilies/emthup.gif

why do you think it stuck closed? after you fill the coolant and run your car it has to reach operating temp before it will open again, then it will suck downa bunch more coolant and you can top it up again. Also you know about the bleeder screw?

I have never really heard of thermal shock either, if that were true then my tstat would break all teh time because when I shut my hot engine off and its -40C outside would be much more of a shock then adding coolant at room temp to a warm or cold engine...

Re: (biggee)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by biggee &raquo;</TD></TR><TR><TD CLASS="quote">why do you think it stuck closed? after you fill the coolant and run your car it has to reach operating temp before it will open again, then it will suck downa bunch more coolant and you can top it up again. Also you know about the bleeder screw?

I have never really heard of thermal shock either, if that were true then my tstat would break all teh time because when I shut my hot engine off and its -40C outside would be much more of a shock then adding coolant at room temp to a warm or cold engine...</TD></TR></TABLE>

Well this most recent time ... I was performing the bleed procedure per HELM. after 30 minutes, my car was 'warm' however, the fan never kicked in. The temp gauge kept climbing past the half-way point, so I decided it was time to shut down. I checked the hoses ... upper rad was hot-as-hell, lower hose was cold. After letting it sit for maybe an hour or two, I pulled out the thermostat. As I pulled on the (closed) thermostat, boiling-hot coolant shot out from behind it. And nearly scalded my hands https://honda-tech.com/forums/images...s/emthdown.gif

Now what's this about the bleeder screw?

-a

Re: (Achenar)
 

its pretty simple to check if the thermo is really bad...

take the thermo inside, and boil some water in a tea pot. put the thermostat in a tea cup and fill the cup with hot water. if it opens, the thermo is not your problem.

Re: (93eg2james)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93eg2james &raquo;</TD></TR><TR><TD CLASS="quote">its pretty simple to check if the thermo is really bad...

take the thermo inside, and boil some water in a tea pot. put the thermostat in a tea cup and fill the cup with hot water. if it opens, the thermo is not your problem.</TD></TR></TABLE>

The thermostat was in boiling coolant. It was closed. Whether or not it is bad is not the question ... the question is WHY ...

-a

on your upper rad hose where it attaches to teh cylinder head there a a 12mm bolt with a nipple looking thing. with your motor running crack that thing open and bleed the air out of the system..

Re: (Achenar)
 

why... pep boys... lol aftermarket parts can do some weird things... u say it served u for three years though not that bad

Re: (seabass10369)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by biggee &raquo;</TD></TR><TR><TD CLASS="quote">on your upper rad hose where it attaches to teh cylinder head there a a 12mm bolt with a nipple looking thing. with your motor running crack that thing open and bleed the air out of the system..</TD></TR></TABLE>

I was bleeding the system with the cap off the radiator. If I do this is there any need to fuss with that?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by seabass10369 &raquo;</TD></TR><TR><TD CLASS="quote">why... pep boys... lol aftermarket parts can do some weird things... u say it served u for three years though not that bad</TD></TR></TABLE>

Yeah yeah ... I just got back from Honda with an OEM thermostat. https://honda-tech.com/forums/images...es/emsmile.gif

-a

Re: (Achenar)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Achenar &raquo;</TD></TR><TR><TD CLASS="quote">I was bleeding the system with the cap off the radiator. If I do this is there any need to fuss with that?</TD></TR></TABLE>

Because not all the bubbles will work their way through to the radiator. The reason that bleeder is there is because that's a spot where air is going to go.