1998 V70 T5 Compression Mystery...

4volvosreally · Post by **4volvosreally** » 25 Sep 2013, 21:49

A couple of days ago my car starting making some strange noises; sounded like I was dragging a tree branch; unfortunately I chose to drive another quarter mile before investigating. I made it maybe 200 yards. A loud bang was followed by a stall, and the next thing I knew I had pushed it into a driveway and was waiting for a tow truck.

A compression test shows:
0, 0, 0, 50, 98

Further investigation shows:
- no water in the oil
- oil not sludgy
- timing belt is loose and not around all the gears.... ??

Questions:
1) what could have caused this? Timing belt was replaced by small shop 20k ago (they may have not done the tensioner)
2) what are the next steps? Pull the head?

Thanks for any and all thoughts.

SpeedyPete · Post by **SpeedyPete** » 25 Sep 2013, 22:00

Since the timing belt jumped the gears most likely the bang you heard was what is known as piston slap. This is when the piston hit the valves in your head. Pull the head.

Post by **erikv11** » 25 Sep 2013, 22:30

What he said. Something caused the timing belt to slip, so valves met pistons and they are bent. Bent valves = zero compression.

Upon closer inspection you may find failed timing parts, like the tensioner or a pulley or even the water pump.

I wouldn't just pull the head, that is an end game maneuver (no turning back). Do just a little investigating to better understand what is up. There is some (tiny, tiny) possibility that just putting the car back in time and the belt back on, with intact timing parts, it will run OK. Definitely worth checking. Tiny, tiny chance.

Then, decide if you want to pull the head (to better assess the extent of damage or just to go about fixing it), or move on etc.

Post by **rspi** » 26 Sep 2013, 13:37

Tiny, tiny, as in 0.005%. Like dreaming that you have found a lot of money and you wake up to find $10,000 lying in the bed next to you. Well, let me dial that back to the cost of replacing the motor, $1,800.

I seriously doubt that a bang you heard was valves into pistons, no one, I mean no one has ever heard that sound. My guess is that something was going wrong with the bottom end, like a crank bearing went (dragging) then it threw a rod (bang), and that caused it to jump timing.

Are you sure there is NO coolant in the oil? Did you drain the oil? If so, was there any metal in it?

There is also a small chance that the tensioner, roller, or water pump broke and made a noise that you could hear.

Look around, if you don't see anything, drain the oil. If it doesn't have any oil in it, decide it you want to drip the oil pan or just pull the head. But the bottom line is that you know it jumped time so at a minimum you will be replacing the head.

You should be able to pull the head in 3 hours.
http://atthetipwebs.com/technologyinstr ... gasket.htm

4volvosreally · Post by **4volvosreally** » 26 Sep 2013, 20:08

Thanks for all the great feedback. I forgot to mention that when we towed the car I found a fair amount of oil on the ground, as well as on the underside near the sump - and on the subframe near the filter.

I was not able to determine where it originated, and the leak did not persist with no oil pressure. I didnt see any metal in the oil, and the oil seemed darker when I drained it (from what leaked on the ground and what I remember it being).

This weekend I will pull the head and let you all know what I find...

Post by **rspi** » 27 Sep 2013, 15:58

Maybe you blew an oil cooler line, if the car is turbo.

4volvosreally · Post by **4volvosreally** » 29 Sep 2013, 19:12

Ok, after considerably longer than 3 hours, I managed to pull the head. This time included the need for an easyout to remove rounded head bolts, bolts that where damaged after a socket split and I failed to notice...

What I am able to see:
- scoring on the top of each piston where the intake valves hit the pistons (all 5 cylinders!)
- head gasket looks ok (to my inexperienced eye)
- no visible damage to the cylinders
- when turning the crank all pistons appear to move fine

It is not clear to me where the oil leaks came from. Could be the turbo, as rspi suggests. Its in pieces now but had some oil in the air intake component.

Also not clear is if I can rebuild with the tops of the pistons damaged as they are.

Another question is how the timing belt got so beat up. Looks like it might have slipped off... Anyone know what might cause this?

I am having a machine shop look at the head in the morning. Finally, if I decide to have the car idle for 3 weeks while I rebuild the head, how do I keep the RMS from failing? I already changed that, and it required dropping the subrame. I decided it is a lift only job afterwards...

Thanks again for everyones time and thoughts.

difflock54 · Post by **difflock54** » 29 Sep 2013, 20:05

Ive read posts somewhere where members have been able to retain the pistons depite them having the valve indentations in the top. Some seem okay from the pics?
The bent valves are the reason for the 0 or very low compression readings.
The belt may have been compromised by a sudden failure of the water pump,tensioner or idler pulley.
Renew the lot now anyway along with all camshaft seals and also the crankshaft seal so you know all is up to date.

It seems that rspi's diagnosis of a possible crankshaft bearing failure can be ticked off the list if the turning of the crankshaft seems smooth and piston function is normal.
As the PCV is all nicely accessible currently I'd be servicing that also to avoid future strain on your new oil seals further down the track.

Post by **rspi** » 29 Sep 2013, 20:33

Well, I'm not convinced that nothing is wrong with the lower end yet. Something went terribly wrong with the timing belt jumping and oil spewing out of the motor. People toss timing belts all the time without loosing oil.

First off, there should be NO concern about the RMS. Cars sit for years without a RMS leaking.

Secondly, as long as there is no hole in the pistons they will be fine. Our pistons had deeper notches in them when I pulled our head off, I'm sure you seen that in our photos.

You have to figure out 2 things: 1. What made that timing belt come loose? 2. Where did the oil come from?

The timing belt situation should have been easy to spot. Spin the water pump and rollers, if they are good, spin smoothly and are tight, it has to be something with the tensioner or crank. Were the cam sprockets secure on the cams? Is the crank dampner still in 1 piece? Was the dampner cover still on? It looks like some screw or something got in the belt path.

From there, work on finding where in the heck the oil came from.

Post by **rspi** » 29 Sep 2013, 20:37

I wouldn't send the head to the shop until I figured out what was going on with the other 2 issues. It may be cheaper and safer to do a motor swap.

I might feel safe with the bottom end after putting a tool on the crank bolt and turn that thing over kinda fast about 10 times.