https://www.matthewsvolvosite.com/forums ... =1&t=66400jblackburn wrote:The thermostat should fail in the open position - nothing should be overheated. The ECT usually throws a code when it notices that the engine is never warming up to temperature.
I've blown 2 heater hoses in cold weather. One at the crimp; the other the brittle plastic connector to the heater core junction box failed.
Don't forget about the little turbo coolant feeder hoses!
850 or aged white blocks cold weather.
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Ben850
- Posts: 1613
- Joined: 8 September 2011
- Year and Model: 1996 850 R Wagon
- Location: Michigan
- Been thanked: 7 times
Re: 850 or aged white blocks cold weather.
1993 850 GLT , You wouldn't know it.
1996 850 Turbo Wagon White.
1995 T-5R Black. New work in progress.
1998 V70 XC Cross Country White.
1994 850 N/A Wagon Black.
1997 850 Sedan Black.
1996 850R Wagon White.
1997 850 Sedan Red ( not white or black!)
1996 850 Turbo Wagon White.
1995 T-5R Black. New work in progress.
1998 V70 XC Cross Country White.
1994 850 N/A Wagon Black.
1997 850 Sedan Black.
1996 850R Wagon White.
1997 850 Sedan Red ( not white or black!)
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jblackburn
- MVS Moderator
- Posts: 14043
- Joined: 8 June 2008
- Year and Model: 1998 S70 T5
- Location: Alexandria, VA
- Has thanked: 9 times
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So the consensus is that they will fail in the open position no matter what? AFAIK that's true on these. Good design there.northernlights wrote:The Wahlers that I have seen fail have broken at the top strap, and as a result failed open. To me it looks like they were designed to fail open, because having a thermostat fail closed is very bad.cn90 wrote: - When the tstat prong breaks, the tstat opens sooner because the spring tension is no longer there ---> engine runs cold.
When I was a kid, we had one stuck shut on a Saab 900, but I have no idea what the T-stat actually looked like.
'98 S70 T5
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
- erikv11
- Posts: 11800
- Joined: 25 July 2009
- Year and Model: 850, V70, S60R, XC70
- Location: Iowa
- Has thanked: 292 times
- Been thanked: 765 times
Are you speculating or you have actually seen this happen, or read about it or something? I think it is not the case ...jblackburn wrote:... The ECT usually throws a code when it notices that the engine is never warming up to temperature. ...
In addition to my own cars (3 broken stats as mentioned), I can't recall a single thread reporting an ECT code as a result of a failed tstat on their Volvo. Granted, I don't always recall so well ...
'95 854 T-5R, Motronic 4.4, 185k
'98 V70, T5 tune-injectors-turbo, LPT engine, 304k, daily driver
'06 S60 R, 197k
'07 XC70, black, 205k
'07 XC70, willow green, 212k
'99 Camry V6
153k
gone: '96 NA 850 210k, '98 NA V70 182k, '98 S70 NA 225k, '96 855 NA 169k
'98 V70, T5 tune-injectors-turbo, LPT engine, 304k, daily driver
'06 S60 R, 197k
'07 XC70, black, 205k
'07 XC70, willow green, 212k
'99 Camry V6
gone: '96 NA 850 210k, '98 NA V70 182k, '98 S70 NA 225k, '96 855 NA 169k
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jblackburn
- MVS Moderator
- Posts: 14043
- Joined: 8 June 2008
- Year and Model: 1998 S70 T5
- Location: Alexandria, VA
- Has thanked: 9 times
- Been thanked: 19 times
It has happened EVERY time I've had a bad thermostat (3) in the S70 and ignored it til I could get around to changing it out a few days later.erikv11 wrote:Are you speculating or you have actually seen this happen, or read about it or something? I think it is not the case ...jblackburn wrote:... The ECT usually throws a code when it notices that the engine is never warming up to temperature. ...
In addition to my own cars (3 broken stats as mentioned), I can't recall a single thread reporting an ECT code as a result of a failed tstat on their Volvo. Granted, I don't always recall so well ...
Seen it happen in other threads as well.

'98 S70 T5
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
2016 Chevy Cruze Premier
A learning experience is one of those things that says, "You know that thing you just did? Don't do that."
mercuic: Long live the tractor motor!
- erikv11
- Posts: 11800
- Joined: 25 July 2009
- Year and Model: 850, V70, S60R, XC70
- Location: Iowa
- Has thanked: 292 times
- Been thanked: 765 times
The voice of experience! Good to know, thanks for the follow up.
'95 854 T-5R, Motronic 4.4, 185k
'98 V70, T5 tune-injectors-turbo, LPT engine, 304k, daily driver
'06 S60 R, 197k
'07 XC70, black, 205k
'07 XC70, willow green, 212k
'99 Camry V6
153k
gone: '96 NA 850 210k, '98 NA V70 182k, '98 S70 NA 225k, '96 855 NA 169k
'98 V70, T5 tune-injectors-turbo, LPT engine, 304k, daily driver
'06 S60 R, 197k
'07 XC70, black, 205k
'07 XC70, willow green, 212k
'99 Camry V6
gone: '96 NA 850 210k, '98 NA V70 182k, '98 S70 NA 225k, '96 855 NA 169k
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