The timing belt tale

98S70T5 · Post by **98S70T5** » 26 Dec 2018, 08:54

Started the TB job on my S70 this weekend. It has been in my family for 13 years since it had 92,000 miles. I have no record of it having a timing belt in its life. Opening the cover showed a Volvo belt with an original style water pump.

From what I can figure all original components made it to 170,000 almost exactly. When I removed the tensioner and idler the idler had some side to side play but the bearings spin freely but feel "dry". The tensioner pulley was 100% locked up! The belt was pretty loose so I presume the looseness in the belt gave it just enough to let the belt slide along the locked tensioner without destroying it. The belt itself didn't look all that bad considering nearly 21 years and 170,000 miles.

Some how by the grace of Sweden we avoided catastrophic engine failure. The job really isn't that hard and I will have it back together next week when I get back to the garage. I will have about 4 hours in it total including replacing the upper and lower radiator hoses.

Thanks to all who have posted tutorial and photos. Very helpful while doing the job.

Post by **abscate** » 26 Dec 2018, 09:04

so I presume the looseness in the belt gave it just enough to let the belt slide along the locked tensioner without destroying it.

YIkes! That could not have been running like that too long.

I think the MTBF of these parts is well past 150k miles, but I am a risk taker. I do counsel people that you don't have to dive into a new-to-you-Volvo and replace TB immediately - take a look at it and if its dry and not cracking, put it on the to do soon list, but not the imminent danger list.

Remember for P2s, if you have the right VIN, the service interval is 150k miles, with the identical parts to the standard interval.

98S70T5 · Post by **98S70T5** » 26 Dec 2018, 09:08

Got it thanks. I don't really mind the job, will most likely adhere to the 70K interval the manual calls for.

Can't wait to get back to driving it. I ran it all last week just to make sure no other issues popped up before I did the belt and drained the cooling system. Averaged 24 MPG and it is fantastic on the highway.

I am a truck guy but I have really missed a smaller more nimble car for city duty.

Post by **abscate** » 26 Dec 2018, 09:49

Its an interesting progression of timing belt interval from early white block years, to the 1996-1998 (70k), to the bastards 1999-2001 (105k, different tensioner), and finally P2 (120k) - all with basically the same stress and similar components.

Post by **misha** » 26 Dec 2018, 10:28

Early 850 '91-'94 had narrower timing belt than models from '95-'97.
S,v70 had the same belt like late 850 up to ME7('99 & '00).

Does p2 have wider timing belt than late 850 and s,v70?

98S70T5 · Post by **98S70T5** » 26 Dec 2018, 10:43

Seems like the belt is never actually the failure point so width shouldn't make a ton of difference in theory. Valve spring pressures and geometry maybe?

I am actually a Mopar guy. In 1992 they made a Daytona and a Spirit in R/T versions that featured a Louts designed DOHC head and they used extremely stiff valve springs. Those cars generally ate up belts far before their scheduled maintinance interval but their SOHC sisters rarely had belt failures even well over the service interval.

Could be a number of factors at play on the belt side of things. Maybe they just didn't know how durable their design was? Either way, I would rather do it 30K early and never make valves meet pistons.

Post by **j-dawg** » 26 Dec 2018, 16:09

I suspect it's more to do with factors driving maintenance schedules - regulations, marketing, etc - and, at some point, engineering agrees to stretch the maintenance schedule by 20,000 miles and go from 99.99999% reliable to 99.9999%.

98S70T5 · Post by **98S70T5** » 07 Jan 2019, 07:40

Update: Had some time Saturday to finish up the timing belt job. All went together great. The lower radiator hose is a little bit of a pain but nothing that patience can't take care of.

The car idles much more smoothly and quietly. It is also much more snappy on a quick rev in neutral. I think the cams must have had a decent amount of retard from a loose/stretched belt. I would qualify the job as pretty darn easy if you did it without water pump replacement. Really doesn't require much skill just slightly time consuming.

Side note: My car wouldn't take coolant via the overflow tank so I just took the upper hose off and filled all the system would take via that. Once it started and the thermostat opened it stayed rock solid on temp all day. I did about 300 miles over the weekend after I got it back together shuffling other cars and people around. After a few heat cycles it sucked in another quart or so bringing the total fill to right about 1-1/2 gallons +/-

Post by **oragex** » 07 Jan 2019, 08:18

Nice save! It is also important to use the good brands for parts on these cars. The belt is quite easy on these engines, except indeed the water pump, on the 2.4/2.5 block it has a gazillion securing bolts some not easy to access with the ratchet because the frame comes close - when you think you them all, yep, there's another one hidden in there

98S70T5 · Post by **98S70T5** » 07 Jan 2019, 09:13

Ha, thanks. Just happy to have it back on the road. I forgot how great of a little car it is.

The truck is put away for winter now. Averaging about 26 mpg so far for the weekend/work week. First real long road trip should be Detroit at the end of the month for the auto show.