98 v70 GLT rough idle when in gear

Post by **stephansvolvo** » 23 Jan 2015, 23:54

Hmm. You make good points. I have been running mid grade not 91. But on the day this happened I filled up with 91 since it was so cheap.imthought the timing jump was wierd.
I didn't think it would turn over either but it has and it did. Once I pull the head, which I've never done, what exactly am I looking at? I haven't found any Volvo videos that show this process. Any that you know of? The one from Robert is good, but id like to know what I'm looking for.

Thanks
Stephan

Post by **mecheng** » 24 Jan 2015, 04:21

Yes, one thing common with a lot of valve burns is a long high speed run so as sad as that seems be careful with the Italian tune up. It seems like the valves don't like sustained heat, so if you want to give it hard do it on a colder day.

Post by **E Showell** » 24 Jan 2015, 12:21

Tracy's True Soaps has the bible post on pulling the head -- Google it. It has been referenced here numerous times. I think the number 2 cylinder issue has something to do with how the manifold branches and what the exhaust flow is. For some reason, I recall a mechanic telling me most burned exhaust valves he saw were either on #2 or #3 cylinder and I recall him saying something about the exhaust gas flow through the manifold.

Redoing the head and replacing the engine with a known good one are six of one half dozen of the other if you are paying to have it done. About 15 hrs. shop labor to do the head alone, but only about 18 or so to replace the engine, so, if you are paying someone else to do it, the difference isn't as great as you might think.

Having never pulled an engine or done an engine swap, I'd have to say if you are going DIY, it is probably easier to do the head only as opposed to the entire engine. Local machine shops can remanufacture the head or you can use a place like Clearwater (folks on here have used them and said good things, but I've heard mixed things there).

Reman head locally or via Clearwater should run about $500 a used engine from a place like Erie VoVo can run you twice that -- with a very good, lifetime warranty, however. Then there are a bunch of incidentals if you are doing a head replacement -- anaerobic sealant, gaskets, etc.

If the car is otherwise robust, or low mileage and carefully looked after, the economics of a head repair/replacement or engine swap can make sense, particularly if you plan on doing the work yourself. If you aren't doing the work yourself and there are a lot of other things the car needs, it may be time for a viking funeral since you might come by a replacement vehicle for what you'd pay a shop to do a head or engine swap.

I've been down this road myself and in my case it made sense to me to pay a shop to replace the engine. If my car were not a manual trans, I am not sure I would have made that call. I've had essentially 44K miles of more or less trouble free motoring with the replacement engine.

Post by **erikv11** » 25 Jan 2015, 09:09

Lots of good advice in this thread. One curious thing that I have seen no previous evidence to support: I don't think high speed runs have any correlation at all with burnt valves. And the engine will get just as hot on a cold day as a warm one, on a high speed run. Valves do burn through (fail) in an instant, but that is after years of oil-leak caused carbon buildup or of running lean etc.

Post by **JimBee** » 25 Jan 2015, 21:45

A simple test I viewed on YouTube was lay the head on its side and pour some liquid into the intake ports. Likewise, the exhaust ports. If a valve isn't making a perfect seal, you'll see the liquid leak through fairly quickly.
If your timing belt jumped, you'd have bent valves. Those you can easily see.

Post by **mecheng** » 26 Jan 2015, 06:50

The colder it is the better the better the heat dissipation for all the components. So while the temp gauge shows the coolant getting to the same temp, the overall peak temps of the components are lower. You can't argue with thermodynamics all heat transfer: convection, conduction, radiation are greater when delta t is greater.

Post by **erikv11** » 26 Jan 2015, 18:43

mecheng wrote:The colder it is the better the better the heat dissipation for all the components. So while the temp gauge shows the coolant getting to the same temp, the overall peak temps of the components are lower. You can't argue with thermodynamics all heat transfer: convection, conduction, radiation are greater when delta t is greater.

Ugh. It's not like we have a rectangle with the word "engine" on it, then outside air, and we throw one equation at it to describe the system. This isn't a true-false quiz on basic physics laws, it is a common sense application. The valves are way inside the engine and right next to the combustion chambers, the engine has heat conducting/convecting fluids (oil and coolant) circulating throughout, and several air chambers (in the head, in the valve cover, the sump, etc) to consider. Cooler outside air does not automatically imply "the overall peak temps of all the components are lower." And don't forget that insulating blanket under the hood, mitigating outside air effects anyway ...

How is it that the outside air temp does not affect the steady-state temp of coolant where it leaves the head (at the ECT), but it does affect an instantaneous temperature at a valve, well inside the head? Can't get my head (pun intended) around that one.

Moreover, I still think there is no evidence that a hot engine burns more valves?? Or maybe you weren't really addressing that anyway. But to beat on that horse too ... an engine that overheats and warps, essentially never shows associated burnt valves. As stated that has more to do with deposits, and/or with running lean (which means hotter burns yes, but perhaps more importantly unburnt oxygen in the cylinders). It's not like we could just run a cooler thermostat and cure the problem.

Don't mean to rant at all, just rattling off some things that occur to me here ...

Post by **stephansvolvo** » 04 Feb 2015, 22:42

So all parts are ordered. Should be able to start this valve job in the next two weeks. I figured since I'll be in there I will replace the PCV, vacuum hoses, Evap system hoses and purge valve, fuel lines to the tank and I hopefully I can find the leak at the top of the fuel tank. When I fill up it like to drip, only when parked in my driveway on the slope. Any ideas on that one?
I plan on videoing this whole process, mainly so I can put it back together with no parts left over. I've never done a job this big, EVER! So I'm a bit nervous and yet very excited to learn.
Any guidance you guys have would be much appreciated. I have watched countless hours of videos, found and read threadss here on MVS so I feel pretty prepared.I guess the proof will be in the ignition when I turn the key to start it.

Thanks,
Stephan

draser · Post by **draser** » 05 Feb 2015, 11:38

So you pulled the head and took apart to assess damage, I did not see that in the post?

Post by **stephansvolvo** » 05 Feb 2015, 21:16

draser wrote:So you pulled the head and took apart to assess damage, I did not see that in the post?

I did not pull the head apart. I have done all the diagnostics and it points to burnt valve(s). My mechanic thinks it more than likely is a valve issue as well.