1998 S70 Yet Another TB Question (not about TDC)

Amphibious Delight · Post by **Amphibious Delight** » 06 Jan 2015, 21:07

Project Blue Diamond - 1998 Volvo S70, NA

The meat:

Replaced timing belt due to (mechanical) tensioner failure. I got everything lined up as it should, turned the engine by crank 4 cycles, confirmed the marks, checked the belt tension, and tried starting the car... which it didn't. The sound the engine makes while turning over is that non-combusting, I'm-not-timed whine. Despite the obvious from the previous statement, I'm convinced the timing is set up correctly (Note: This was not a one-shot deal. The story is too long for this post...)

My question is, could valve damage prevent the engine from starting at all?

Any need to quit beating about the bush and remove the head based on probability and all the variables?

The potatoes:

I've been lurking on MVS for several weeks now doing research on this jewel I picked up on the cheap as a project. Only 145k, clean, and straight. Cosmetically, I'm astonished this thing is 16 year old. I went into this knowing that I might have to pull the head. The strategy was to replace the belt (along with new tensioner, idler, and water pump) to determine if I was one of those 1%-ers to sneak away with no valve damage.

The S70 is not my daily driver, yet. I have a 97 Jetta (I got a newer car!) with 240k that will be replaced by the Volvo. I am mechanically inclined and consider the valve repair within my skill range, but I've never worked on a Volvo before. My family owned a 93 850 and I loved driving it. When I came upon this one at $500, I was already considering replacing my car and the project fit my budget (Dave Ramsey would be proud).

Any help, advice, or "atta-boy"s appreciated.

Post by **Ozark Lee** » 06 Jan 2015, 21:50

Unfortunately the odds of having the tensioner fail while the engine is running and not getting valve damage is pretty low. Not quite Dave Ramsey recommending a CITI credit card low but in that same zip code.

The way to tell for sure is to do a compression check. If you come up with zeros then it sounds like you know what the next step is. It is a very doable project.

...Lee

Post by **cn90** » 06 Jan 2015, 21:52

Do a engine compression test dry and wet and you will have the answer. I am afraid the valves were already bent when the mechanical tensioner went bad.

Post by **kahl** » 06 Jan 2015, 22:06

I am curious to know what the cam timing marks were at in relation to the crankshaft when the timing covers were removed. From what I understand if the cams are off by more than 2 teeth you will have piston valve impact. I would start with the basic cylinder compression test.

Post by **mecheng** » 07 Jan 2015, 12:00

Never heard of a mechanical tensioner going on these cars. Did it free-wheel? Was it the OEM INA brand?

Post by **erikv11** » 07 Jan 2015, 13:58

There are many reports of the mechanical tensioner failing, with a bit of searching you can get some details about various experiences. The mechanical tensioner is much less hardy than the hydraulic unit.

Post by **precopster** » 07 Jan 2015, 16:09

Yeah if the tensioning spring fatigues and snaps there goes your valves.

The white (or blue if 10 valve) plastic spacer prevents total bottoming out of the hydraulic tensioner however more components means more to go wrong in theory in the older system. Needle rollers for the pivot system have to be lubed as well as the roller on the tensioner roller.

Service interval times were adjusted (increased) accordingly by Volvo as a result of progress.

Amphibious Delight · Post by **Amphibious Delight** » 21 Feb 2015, 19:03

Thanks for all interest and replies!

Update - Did the compression test. Let's just say...I quit at cyl # 4. The head is off and the situation is catastrophic. 6 valves are stuck open. There are witness marks on all of the them...and the pistons. So, I'm now trying to make a decision here. 1) drop $1k for a new engine, 2) cut my losses and sell it as is, 3) Part her out.

One last question... is the damage to the pistons significant? I know they can create hot spots...but let me bounce this off of the collective site...what if I rework the head and run the block as it is. How for do you think I will go before I just wind up "burning" the valves? Has anyone experience with this?

Post by **Ozark Lee** » 21 Feb 2015, 19:29

Post up some pictures. The top of the pistons has dimples for valve clearance by design and they can look like piston damage that isn't damage at all.

...Lee

Amphibious Delight · Post by **Amphibious Delight** » 21 Feb 2015, 19:44

Ok...there's hope. I looked at some replacement pistons online and didn't see any impressions, so I just figured the tops were gouged. Pics to follow...