Hi just bought a 1996 850 T5 Estate with 86k miles on the clock, hopefully this is not a stupid question but having never owned a turbo car before could this be symptomatic of turbo? Having covered around 300 motorway miles driving since purchase I've noticed that the running temperature on the gauge rapidly fluctsuates between 1/4 to 1/2 hot on a long run depending if the turbo is under load or not or if you are cursing say down hill with your foot off the pedal.

Let me try and explain, say you a travelling up hill with the turbo under load then the temperature will immediately rise to 1/2 hot, once you descend the other side of the hill then immediately the temperature gauge will fall to just over 1/4 hot. This fluctuation in temperature in such a sort space of time seems a little unusual, however in town/stationary traffic it sits at a 1/2 all the time? Could it be an electrical fault or machanical problem or do 850's do this?? Hope you can help - regards Markh

 

Check the thermostat sounds like it might have broken.

 

01) Volvo OEM Thermostats have "Wahler, Made In Germany" stamped onto them. Purchase a Wahler 87C/190F thermostat from FCP in Groton, CT. Insist on an 87C made by Wahler. Ask to include the rubber gasket.
http://fcpgroton.com/volvo850cooling.htm
VOL-271417 - Thermostat and O Ring - 87 Degrees - $9.00 - Vernet (OEM)

Verify that it arrives a box with red sides and blue top and bottom in white letters,
Wahler Thermostat Made in Germany and Part Number 4272 87D stamped on the front. Verify that it "Wahler, Made in Germany" inscribed along the top, and "87" inscribed on the bottom.

02) Next, you will need to have a long Torx-40 bit. If you are unable to purchase one from a dealer like Snap-On...

http://www.mcmaster.com/
(630) 600-3600

Enter page number 2609 in search field.

http://www.mcmaster.com/ctlg/DisplCt...CtlgPgNbr=2609
3/8" Square Drive, Long
T30 5" Length 6939A84 13.84
T40 5" Length 6939A87 13.84 <--
T45 5" Length 6939A88 13.84
T50 5" Length 6939A89 13.84

03) Purchase Permatex Ultra-Blue Sensor-safe RTV. You will not use it for thermostat housing. Rather you will need apply a very thin layer on Torx bolts to prevent them from rusting.

04) Purchase PB Blaster to soak sides of torx bolts holding down thermostat housing.

05) Purchase 3/8 inch rubber fuel line hose about 2 feet in length. You will place this over petcock at back of block on passenger's side. Then, you can drain about 3 quarts of coolant into a plastic jug without spilling it all over the floor of your garage.

06) Might as well, purchase Volvo OEM Engine Coolant Temp (ECT) sensor from your neighborhood dealership -- Part Number 9186486 listed as 9186486-8 IAT sensor, at $63.40.

It is incorrectly listed as an Intake Air Temp (IAT) sensor. This is the correct part, as the old one on my car had the same part number stamped on its side.

http://thevolvosite.com/shop/index.p...&car_model=850
Coolant Sensor (also called the IAT sensor or water temp. Sender)
[Genuine Volvo] 9186486 $ 45.00

I had a very difficult time disconnecting the old electrical connector. The plastic cover would slide, the wires would not come apart. I pried up on the flip-up door on the sensor side of the connector. Then, I was able to gently use pinch-nosed pliers to pull apart the wires.

07) Follow these procedures...

http://www.volvospeed.com/Repair/thermect.php
http://www.volvospeed.com/Repair/thermect2.php
http://www.matthewsvolvosite.com/tstat.php

Lift up and remove aluminum cover from fuel rail. Remove two bolts securing fuel rail to intake manifold. Slide fuel rail over 1/8 inch to allow long Torx-40 bit to fit squarely on Torx bolt at rear of thermostat housing.