1998 Volvo V70 misfiring in cylinder 3 no compression

heyarnold · Post by **heyarnold** » 14 Apr 2014, 06:11

Hi everyone, first of all I'm new to this forum so apologies if I have made any mistakes posting this thread, i.e wrong section (hopefully not).

Anyway on with my problem, hopefully some of you will be able to help me out. My dads 98 V70, 2.5L non turbo with about 220k km's on the clock was shaking and he suspected a misfire so he asked me to take a look. To be honest I was very surprised with how well it drove, it seemed to have plenty of power when accelerating and climbing hills, the only real sign was it shook a lot at idle and low speed, otherwise I probably wouldn't have noticed it, although I have never really driven it before. Apparently it had started about a month ago and he carried on driving it up until now. He did also mention around the time it had probably got a bit low on oil, I don't know whether this is connected.

I noticed it was not firing in cylinder 3 at all so I checked the spark plugs and when I took the leads out they broke and the plugs were well in need of being replaced so I replaced both plugs and leads but this didn't fix the problem, they needed doing anyway though. Tonight I have checked the compression and cylinder 3 only put out 30psi, and with oil 40psi. Here are my full results
Dry
1- 200
2- 200
3- 30
4- 220
5- 205
with oil
1- 250
2- 270
3- 40
4- 265
5- 230

So clearly there is a big problem with cylinder 3, and from checking the compression with a cap of oil in each cylinder I don't think its the rings as obviously it didn't really improve in #3. I've read it could be burnt valves and thought this was most likely but when he mentioned it had run low on oil, I thought possibly a blown gasket, would this be possible or would compression be low in another cylinder too?

As I'm sure there's many experts out there, or more knowledgeable than me anyway I hope some of you can put forward your opinion or help me out as best you can. How can I further inspect this?..remove the head?..how hard is it to do this? Any help at all really

Thank you all in advance
Henry

Post by **E Showell** » 14 Apr 2014, 08:09

Burned exhaust valve on #3 cylinder is a quite common problem on these cars at this age. Any chance you can get a boroscope down there and take a peek? It might not give you a sufficient look, but you never know. Beats taking the head off to investigate.

Post by **rmmagow** » 14 Apr 2014, 08:11

Can valves stick in these engines? Can a sharp rap to a valve stem help free it? I've had this happen to a non-volvo that sat for too long and the rap freed up the valve and gradually the engine ran normal again. Burnt valve is more likely and head removal required. Look here, it seems like a real PITA but might not be so bad for someone with experience.

Post by **erikv11** » 14 Apr 2014, 08:15

Burnt valve is by far most likely, you are in the right track. You could do a leakdown test and wee where it is escaping, intake, exhaust (both would be valves) or crankcase (would be rings), or use a boroscope (although I have heard it can be tricky), or pull the head and see it up close and personal. I would do the leak down test, my money is it will leak to the exhaust side, that confirms a burnt valve.

Pulling the head is not bad but definitely takes some time to be done well, there are several guides out there now, I think this one is the best although it is written for a non-turbo (which I assume yours is from the compression numbers?): Volvo 5-cylinder: How to Replace the Head Gasket

Post by **erikv11** » 14 Apr 2014, 08:17

The fix recommended to me for stuck valves is to drive around for 5 minutes in low gear (very high RPMs). I've never had it pay off, the three cases I've worked with all turned out to be burnt valves, but worth a try for sure.

heyarnold · Post by **heyarnold** » 14 Apr 2014, 08:39

I don't own a boroscope and I can't think of anyone I could borrow one from, would it be worth seeing if a garage would do this for a small cost?

"it seems like a real PITA but might not be so bad for someone with experience." I'm not experienced, but I'm a quick learner and I'm willing to give whatever job a go if I think I have a chance.

I've never heard of a leakdown test, will I need any gear for this, is it easy to do? Also yes this is a non turbo, and I've been looking through that guide for the last hour or so. Is everything removed in that guide needed to be removed just to take the head off?

So is there a possibility its just a stuck valve and no damage to it? I will give that suggestion a go, how high rpm's are we talking, just below redline? Also for this, should I be disabling the 3rd fuel injector so it doesn't spray excess fuel in to the cylinder?

Thanks for your suggestions guys, its appreciated. I would of quoted you all to make my reply clear to read but I couldn't find a multi-quote option?

Post by **cn90** » 14 Apr 2014, 09:02

I am with erikv11, I am afraid this is burned valve.
Tons of info in forum how to rebuild a head.

Post by **rmmagow** » 14 Apr 2014, 09:09

Borescope, any decent garage should have this but the leak down test should be available from any garage worth its salt. A good indy service station or better yet somebody who knows Volvos. Basically this involves installing a part like the compression tester and pumping air into the cylinder when both intake and exhaust valves are supposed to be closed. If you hear air hissing in the tail pipe, exhaust valve leaking, in the Throttle body, intake leaking, unlikely, but if you hear air under the oil fill cap, could be rings leaking. A garage should be able to run this for you. If you wanted to try it yourself, you would need at the very least a good air compressor. I would have the leak down test done before trying to hi rev the motor. Don't exceed red-line and disabling the FI makes sense. Tracytruesoaps is perfect for doing the head job. Well worth doing.

heyarnold · Post by **heyarnold** » 15 Apr 2014, 00:35

Okay so my next step will be enquiring about getting a leak down test done from a garage, and maybe see if they'll stick a borescope in there too. Does anyone know how much it would cost in all replacement parts if I did take the head off, i.e head bolts, gaskets, valves etc? I'm in Australia too, would they be easily available? Thanks for the help

Post by **erikv11** » 15 Apr 2014, 07:23

Borescope will likely be expensive, I don't know that it is worth it, a leak down is pretty definitive.

If you DIY the head job (but have a machine shop fix the broken valve) then you are looking at about 700 your cost. This includes all the timing parts, cam seals, stuff like that. If a shop does the work the cost goes way up, at least 1200 total cost I would say. There are a lot of posts about this, you may want to do some searching on the forum here.