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97 850 t-5 temp gauge issue

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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Year and Model: 1997 850 T-5
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97 850 t-5 temp gauge issue

Post by Stonlee » Wed Jun 15, 2016 3:11 pm

Hey! This is my first time using a forum site so I'm not to familiar with the way things work, but first I'd like to say thanks in advance for any responses I receive.

This afternoon my 850 would not start after 3-4 attempts. I inspected the engine bay for any obvious signs of a malfunction but not seemed out of the ordinary. After ten minutes I turned the key once more, this time she started but was stumbling at first before evening out at 1000 rpm.

I let her idle for about ten minutes before pulling out and driving home. Along the way I noticed several issues. The first was a lag in the acceleration. That eventually went away. After a few blocks I then noticed the temp gauge was not moving at all. I pulled over and wait a few minutes before starting her back up. This time while in park and idling the rpms rose to just over 2000 and stayed there till I put it in reverse.

I drove the rest of the way home and did not notice any other issues along the way. I'm completely puzzled by all this and am wondering if these issues are even related.

Any ideas?

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Re: 97 850 t-5 temp gauge issue

Post by Clemens » Wed Jun 15, 2016 3:52 pm

If the temp sensor for the motor is faulty it could cause issues as you describe. i just don't know if it is the same temp sensor that feeds the temp gauge. The one for the gauge is right where the thermostat is (upper heater core). One of my 850ies has a similar issue with the temp gauge, either it works just fine or doesn 't work at all. Comes and goes.

How old are your plugs, wires, rotors? Bad plugs and a faulty wire caused no start issues followed by rough idling till all the excess fuel was out of the motor.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

Ozark Lee
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Re: 97 850 t-5 temp gauge issue

Post by Ozark Lee » Wed Jun 15, 2016 8:29 pm

Classic symptoms of a bad ECT (engine coolant temperature) sensor or a bad connection to the sensor. The connectors are prone to failure for some reason so start there. We have a temperature / resistance chart for the sensor in the repair database but if you are getting hard starts, poor idling and no gauge then it is pretty much a slam dunk that it is bad. The cars a bit picky about that sensor so it is advisable to replace with OEM or the SWF brand which I think is OEM. I have had OK luck with the aftermarkets that I have purchased but others have not done so well with them.

The sensor is located just below the thermostat cap and it is SOP to replace the thermostat and the sensor at the same time since you need to remove the thermostat to get to it. The original Torx head bolts are aluminum and they have a nasty habit of stripping out when you try to remove them. Volvo has substituted some coated steel bolts as a replacement and they are fairly cheap and really handy to have on hand before you start. Letting the bolt heads soak with PB blaster a day in advance of attempting removal can also help quite a bit.

'94 850 N/A 5 speed
'96 Platinum Edition Turbo
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

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