I had '97 850 2.5 20v which i drove for 26 years.
Bought it almost brand new back in 2000 with only 70k km.

Car had around 450k km when engine burnt a valve on 4th cyl few months ago.
Never changed transmission oil,since Volvo says "sealed for life" and never had any problems with it.
Never used ...

I had similiar problem on 850 where i had all 4 brand new summer tyres with 40-45 g/ of weights per wheel on 3 of them and 70g on 4th one.

I had vibrations where whole car was shaking from 120-140km/h....so you could drive up to 120km/h or 140+.
Balanced them 5 times and every time was a bit better ...

How much weights you have on wheels?
If you have 40-50 grams per wheel,wheels or tyres are bent.

Like others mentioned...it could be propshaft or coupling.

What do you mean?
Bosch,Mann,Mahle(Knecht),Delphi fuel filters are all the same size as oe Volvo.

Roll-over valve.
It prevents fuel leaks from the tank in case of an accident where car could end up on the roof.

Should be roll-over valve...inside of rear right wheel...can't really see clearly.

Usually...on later cars with m4.4 there should be a FPR,but yours with LH Jetronic is on fuel rail.

Btw....that fuel filter isn't secured properly on it's bracket and those fuel lines from fuel filter are not safe ...

I'm curious if anyone has tried the GSP branded axles at Rock Auto?

Neil.

GSP is pure Chinese brand.
I once had a chance to check out their CV boots since Gkn wasn't available and as soon as i opened the box i was disappointed.

In comparison with GKN cv boot kit,GSP clamps were so thin and ...

On these cars....paper gasket and new bolts with a sealant on them which comes in the box with new water pump is enough.
Sealant shouldn't be used,just a smear of grease to keep it in place for easier installation.

Which water pump did you used?
Did it come with brand new bolts with sealant on them ...

Service light is a service(oil change) reminder and it says SERVICE.
It turns itself off after a few minutes after starting the car .
Yes...these cars have it.
There is a separate submenu on Volvo diagnostic tool for clearing service light.

Clearing engine codes or codes from other modules in the ...

The dash cover pulls out a bit then needs to be lifted up in order to remove it.

Passenger side airbag stays on the dash cover,just disconnect orange connector for it which is behind the glove box.
When you remove it,you will see it.
Every upper side vent grilles needs to be removed to access ...