2000 S70 Timing Belt: Why the VVT Preload?

Post by **deepsouth** » 07 Jun 2016, 16:51

Hey all--
A couple weeks ago I replaced the timing belt, related components, and water pump on my 2000 S70 Turbo. Aligned the crank mark, made sure the the cam marks were correct, removed tensioner, idler pulley, and water pump. When I pulled off the old timing belt the cams didn't move at all (nor did the crank). Same amount of teeth between cams on new v old belt, etc... Reassembled with no problem and cranked up--runs great.

Two weeks later (and around 500 miles) I get a p0014 code which I understand is a timing code and many say is related to preloading the exhaust VVT cam. Car still runs great. Here's what I don't understand:

1) If nothing moved when I pulled the old belt and I simply swapped belts why would I need to preload the VVT? (Mine is on the exhaust cam).
2) I've watched many videos of many P2 timing belt swaps, including this one by FCP, and the following one by 1AAuto and they mention nothing of preloading.

https://www.youtube.com/watch?v=IK_zH8g8Fow

https://www.youtube.com/watch?v=Emsa-w-n93s

3) I've noticed many Volvos with VVT hubs on exhaust, some on intake, and owned many with none at all (hydraulic tensioner and very simple timing belt replacement). Is this preload procedure the same regardless of whether or not the VVT hub is on intake, exhaust, or both?

Here are my marks before pulling off the belt:

Marks were in same place after replacing pump, idler, and tightening tensioner (taking into consideration the temp factor and the eccentric, which I started at seven o'clock and tightened up to around 11). Again, the car runs great. Erase code and it will pop back up as pending but wont throw MIL until around 300 to 500 miles (roughly two weeks of driving).

What have I done wrong? If it's the preload I understand how to do it, I just don't understand why it's needed when nothing moved from old belt to new. I don't mind pulling the new belt off, rotating 90 degrees past, backing up, removing belt, etc... but do I really need to?

I'm about to do same procedure on my 2001 XC70 (also with VVT on exhaust) so any help understand why this is needed and how this system works is greatly appreciated!

Eric
Athens, GA

Post by **MadeInJapan** » 07 Jun 2016, 17:59

I'd like to know too. My friend's '03 C70 has that exhaust VVT and hers is giving her that same code. During colder months, it seemed to keep her car from starting on occasion. I told her I'd help her sort this out. I though the CVVT solenoid might be gunked up.

Post by **deepsouth** » 07 Jun 2016, 18:08

To me, preload implies that by removing the old timing belt it somehow unloads the cam VVT. I'm not sure how that happens since nothing moved. Further, I've watched plenty of P2 Volvo timing belt videos and no one talks about preloading the VVT hub. The only time I ever preloaded the cam was when I pulled and rebuilt the head on my 1999 V70 and removed everything. It'd be great if someone who understands how this works can explain it. And also address why all of the videos show a simple belt replacement once the marks are aligned.

My problem is that clearly something changed because before this job I never had a p0014 code. I'm assuming that I don't need the preload procedure and perhaps my cams rotated ever so slightly (even though I was very careful) so that the belt grooves were still the same but i was a bit advanced. I'd like a second (or third and fourth opinion though).

The last time my 2001 XC70 had a clogged VVT solenoid it popped a code. From what I understand the preload is on the VVT cam/hub.

Post by **cn90** » 07 Jun 2016, 20:26

As long as the TB is on the same marks for all 3 areas (crank, intake hub, exhaust hub), then the problem is elsewhere.
The idea of "preload" (or CW first then CCW) is just to engage and disengage the spring tension inside the VVT.

The fact that you have a new problem 500 miles later points to the solenoid as the culprit.

Post by **MadeInJapan** » 08 Jun 2016, 06:12

Aha...thought it might be the solenoid! So, now- does anyone know what to do- how to service that solenoid? Are there any good write- ups on that? I have read there's a screen in there that starts to get clogged and pathways...they also sell new solenoids that may be a solution too. If I recall, they aren't an arm and a leg.

Post by **deepsouth** » 08 Jun 2016, 07:51

So, for clarity, the only reason one would need to preload is if the spring loaded hub unloads when pulling off the old belt?

I've changed the solenoid before, four 10 mm bolts and a new gasket/screen--bought a used one on eBay for around $35. Very easy 20 minute job. At the time it popped a VVT Solenoid code P1332.

I guess I'm wondering why wouldn't it throw the same code (P1332). Today it started throwing the P0014 immediately after reset. I'm going to recheck timing and tensioner tonight after work to make sure everything is okay. That bottom crank mark is very tough to see with the tensioner in place.

I want to believe it's something as simple as the solenoid but it seems like an awfully big coincidence that I just did a TB job!

beoutside · Post by **beoutside** » 11 Jun 2016, 18:17

It sounds like some vvt pulleys have a spring loaded exhaust pulley and some don't ??? .... I need to figure out this as well since I have 99 xc in which I thought had a spring tension vvt but when I redid the seals, timing belt, water pump at 260000 and put it back together no spring tension?? tried just rotating the pulley with a snugged torx 55 bolt and no luck either. Any info on testing / checking the vvt to make sure it working properly would be appreciated and Ill double check my alignment per Lee's post . thanks re 0014 advanced timing code.

When I redid the head at 180,000 I was sure there was significant spring tension on the exhaust vvt pulley and I had to hold it while resetting the belt while marks lined up. It has always run well....
Thanks !

Post by **Ozark Lee** » 12 Jun 2016, 06:23

If you look carefully at the exhaust cam sprocket you will note that the sprocket and the center of the hub travel independently over a short range which is why the mounting bolts are in slotted holes. The preload process puts those mounting bolts in a more central location during normal operation so that the valve timing can be either advanced or retarded by hydraulically varying the position of the center hub relative to the sprocket. The actual cam position follows the center hub, not the sprocket position.

When the preload is properly set the mounting bolts will not be at either limit on the mounting hole slots. It will rarely be centered in the slots but it should not be all the way to either extreme.

...Lee

beoutside · Post by **beoutside** » 12 Jun 2016, 07:51

Thanks Lee , so I can assume when the exhaust vvt hub is either snug or torqued to proper specs the pulley should rotate that few degrees under spring tension and return when released . Mine does not ..... But I am fairly sure it did last belt change, If it was over tourqued on at some point maybe that damaged it or it has just failed? I will look this morning to make sure I am not off a tooth in timing . Thanks again Donny . PS I have not had any other value problems or bypass burning oil from the exhaust since I redid the head and replaced all hydraulic cam followers/lifters..... Now at 260000 roughly.Appreciate your help.
Donny
Big fan of the cam looking tool

beoutside · Post by **beoutside** » 12 Jun 2016, 15:10

redid it as you said purrs now vvt working , not sure what i missed !!!