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Compression Test Results: Cause of Vibration?

3580 Views 36 Replies 9 Participants Last post by  Dave A.
I know this another thread concerning the same engine vibration problem mentioned in my other thread ("Need Expert Help-Engine Vibration Still There") and I apologize for dropping this on another thread, but I received the results of the wet and dry compression tests from the dealer today and wanted to see what your feedback would be.

Short synopsis: tranny rebuilt six weeks ago, new clutch, pressure plate, timing chain, water pump, front oil seal installed. Engine ran fine when taken to the shop to begin with. Just completed complete tuneup before tranny work was started. After picking car up after work was complete, there was an engine vibration at about 1250-1300rpm (with clutch in or out sitting still) that we have just not been able to pin down. Tranny removed again, ANOTHER new clutch and pressure plate installed, still vibrates. ANOTHER new timing chain installed and timing re-checked (dead on). Still vibrates. Crankshaft pulley (which had a piece cracked out of the edge) was removed and engine ran briefly to check. Engine still vibrates. We have done EVERYTHING we can think of to isolate this vibration and found nothing.

Today the dealer did the compression test and found the following:

Cylinder--Result Dry--Result Wet
1 145 185
2 155 190
3 120 170
4 155 185
5 150 186
6 120 170

'85 P type 5M-GE engine, 353,000 miles, engine never been opened (other than a couple timing belts). Car was running GREAT before took it for the tranny work, no vibration, still getting 320-330 miles per tankful of gas. Ran smooth (used some oil, but with that many miles rings are obviously 'worn' to say the least).

Obviously it appears that cylinders THREE and SIX are definitely loosing compression. Question is, could this cause a vibration that is NOT there at idle, but kicks in at 1200-1300rpm? If so, can anyone venture a guess as to WHY this would be so apparent now and was NOT even there or noticeable before? If it is a compression problem, I do not understand how it just 'appeared' after this work was done. I don't doubt the results of the test and I don't doubt the rings are WELL worn, I just do not understand how this would not have been a 'coming on over a period of time' problem as compared to a 'shows up all at once' problem.

I have been restoring this car over the past year and half (looks really great on the exterior and working on the interior now) and have been planning to have the engine rebuilt. If it does require rings (and I'm sure it does) would it be best to just go ahead and have the rebuild done now, in comparison to what I will have to spend just to have the rings done? It would not 'seem' prudent (to me) to do that work to it, without going ahead and doing the 'whole thing' seeing as that was in the plans anyway (just wished it had been sometime AFTER Christmas!).

Any feedback, as usual, is greatly appreciated!
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Hi I had tests done on my car to track down a miss.....they where similar to yours ( to be honest they varied more ) but where not the problem.....my car has 200,000 plus klms on the clock and is in need of a rebuild accoring to my garage but still idles and runs smooth so i dont think the problem is your motor, remember it was good as till ya trams work was done so it has to be in that area somewhere, maybe the trans itself is causing the vibration.
Well, in our tests (before compression tests) we re-checked everything relative to the tranny (besides installing ANOTHER rebuilt one) and no joy. Besides, the vibration is still there even with the clutch pressed to the floor and some have specifically responded (as was my thought) that with the clutch pressed in, the tranny is TOTALLY dis-engaged, thereby removing it as the 'culprit'. Another new clutch and another new pressure plate were re-installed (thinking those could be off somehow) and still the vibration.

But I appreciate the feedback; that is good to know that your results were similar with no vibration. I really cannot believe myself that bad rings would just 'pop up' all of a sudden with a vibration like this that had not been there before.
Explain again, how bad is the vibration???? Big noticeable vibration, or a subtle one, like a buzzing bee????

To rule out this other possibility, can you make them change out that damaged crank pulley & put a good one in???
CJSREDPRA said:
Explain again, how bad is the vibration???? Big noticeable vibration, or a subtle one, like a buzzing bee????

To rule out this other possibility, can you make them change out that damaged crank pulley & put a good one in???

Chris-

No, not a 'big' vibration, but noticeable especially when you hit that 1250-1300 range. As an 18 year driver of this car, obviously I'm going to notice it right off (and I *did* notice it right off), but it's not like the engine is flopping and sputtering and such when it sets in. It just vibrates through the steering wheel and you can 'feel' it in the car. But it is not, like, 'knock you in the head' kind of a thing. But, it should NOT be there and was NOT there when I first took the car in.

On the pulley, they ran a quick test with the old pulley off (everything powered by it - belts obviously - off as well) and they say in a 'quick' run, the vibration was still there (was hoping this was the problem from nearly the beginning, since I noticed, as mentioned in the other thread that a portion of this pulley - the back 'flange' part - as broken off; kind of a cresent moon shaped section). I thought (and others have said also) this *might* could cause a vibration, so they did that test. BUT, others have stated they have the same kind of a cracked off section and they have no vibration. So, go figure. I guess if I sqwawked and sputtered they probably would put on another pulley 'cause they are about as tired of this as I am (if that is possible). At this point, we are all so thoroughly miffed as to be ready to try some 'wing of bat' and 'powered newt' if we thought it would fix my baby!
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Okay, it's a subtle vibration that you can just barely feel?? And it only happens at certain rpm's??? I would say that this more or less qualifies as a harmonic vibration... Make them replace the crank pulley w/ a good one & see what happens.
CJSREDPRA said:
Okay, it's a subtle vibration that you can just barely feel?? And it only happens at certain rpm's??? I would say that this more or less qualifies as a harmonic vibration... Make them replace the crank pulley w/ a good one & see what happens.
Chris-

Even though, as I just posted, that with the pulley off in a quick test the vibration was still there? Would that not tend to rule that out as the culprit or would a test with it removed be an 'invalid' test? (and others have reported the same basic 'damaged' pulley with no vibration). If you feel strongly (personal experience??), then hey, like I said, I'd be willing to try it.
IMHO, to me.... the test w/ the pulley removed is invalid.

Yes, some peeps have no problems w/ a busted crank pulley, some have.

Same theory here for peeps who have switched to a lightened underdrive crank pulley that does not have a harmonic balancer on it. Some peeps don't have problems, others have noticed the vibration & went back to the stock pulley. Vibration goes away. Thus one of the reasons why we don't recommend underdrive crank pulley's, unless they have a harmonic balencer on it.

To me personally, a damaged pulley in this case, sounds like this is what's messing things up.... Along w/ the fact that it happens only at certain rpms, not all the way through the rpm range.... And let me confirm this.... There were no vibrations at all previously BEFORE the crank pulley was damaged, correct???
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Earl,you called Nix and talked to me,and I have been reading all the posts,and thinking about this ever since.
I have to agree with Chris,though I am one of the guys,that has had the chip,w/no vibration.It's either that or they somehow messed up on the flywhell,clutch assembly.
Your compression is still within 10% basicaly,so I would leave the rest of the engine alone for now.
If you could make it move around in the RPM range,with teaks here or there,then I would say it's a tuning problem.But,with it always at the same spot,your option are crank pully,or clutch assembly,especialy since those are what has been messed with.
Well, there was positively no vibration before I took the car in for the tranny work. None.

Now, as to the pulley, I had not *noticed* that it was damaged before (and I had, just a month or so before, on separate weekends, done a complete tune up job and replaced the power steering hose set and pump, so I was under the hood quite a bit there just before this all happened). The cracked off naked edge looks pretty dang fresh. I noticed it was broken the afternoon two Fridays ago when I brought the car home after the tranny work (there is also a 'rolling' vibration there at 45-50 mph whether you are in gear or with the clutch pressed in; we haven't gotten to solving that one yet). I parked the car at home as soon as I got home with it that Friday and took it back to the dealer that next Monday morning. But in my first glance under the hood after getting home with that Friday trying to uncover the problem (loose plug wire, etc....something easy I thought) I saw this damaged pulley and it was something I had not noticed before. So, I cannot SWEAR that it was not damaged before this work was done, but I *think* I would have noticed it if it were. Also, they took this pulley off while it was being worked on to replace the front oil seal (also had water pump installed as well; just misc stuff I wanted done while it was 'in the shop'). My feeling is the pulley was damaged at the dealer, but I can't *prove* that, really. It would make sense it could happen, as I understand they can be a bear to get off (but shouldn't be damaged if using the correct puller, I'd think). I don't understand the exact makeup of the pulley as to it's 'harmonic vibration dampening' design, but I kind of wondered myself if the test with it 'off' was really valid or not. If this is a 'dampener', might it not vibrate *more* with it off? I dunno.

Your line of questioning though is, I think, on the mark, and is some of the same questioning I've been doing.
So, folks have some vibration problems with non-factory pulleys?
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Junkie said:
Earl,you called Nix and talked to me,and I have been reading all the posts,and thinking about this ever since.
I have to agree with Chris,though I am one of the guys,that has had the chip,w/no vibration.It's either that or they somehow messed up on the flywhell,clutch assembly.
Your compression is still within 10% basicaly,so I would leave the rest of the engine alone for now.
If you could make it move around in the RPM range,with teaks here or there,then I would say it's a tuning problem.But,with it always at the same spot,your option are crank pully,or clutch assembly,especialy since those are what has been messed with.
Hey, Shawn! Yes, I did call. And yes (yikes!) I'm still dealing with the same problem. On the clutch/pressure plate, they went back in (thinking that was the problem) and RE-replaced the ones they had put in with the rebuilt tranny and that did not solve the problem. So, kind of eliminates those two items as the culprit. Yes, I do recall you saying you had a chipped area on yours (and a couple other have said the same) with NO vibration. Can you state just how big your 'chip' is? Mine, if measured around the 'arc' of the area that is missing, would be about two inches long probably, and would come in about a third or half inch from the outside edge. Pretty much like a cresent moon shape. It's pretty noticeable when you look down at it (when it is turned in the proper orientation to see it). The timing 'nick' is still in place but the piece that is missing is on this same 'back flange' area that the timing nick is on.

Do you guys (and gals maybe?) really think that with this little bit of missing 'mass' that it could cause this kind of vibration? Again, I don't know exactly how the pulley works in its 'harmonic balancer' roll. I don't have one in front of me to really look at and I have never taken mine off.

Thanks for all your various inputs though; it really is greatly appreciated!
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The size of that "chip" could do it.I have seen several with same size or smaller,but that sounds rather large.
If you look closely at the outer part/front of the pully,you will see a "rubber" spacer,seperating the part that attaches to the crank,and the actual pully portion.
To let you in on what they did/didn't do.They used a friggin' pry bar instaed of a puller to get this pully off.Most times they come right off,but in some cases,a puller IS REQUIRED.The mechanic got lazy,trust me,been there,done that,PERSONALY.
I would also be inclined to wonder what the t-bely pully on the crank looks like.It can also be a biatch to remove,especialy when the balancer was/is difficult.The t-belt pully is very soft,and will bend/break off bits also.I purchased the correct puller for these as well.Considering the tool was about $50,and t-belt pullys are about $50,I figured the first time I needed it,it paid for itself.
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Hmmm......this is getting interesting. Yeah, I wondered what one would have to do to get that thing off, and if some mechanic was in a 'hurry' they might resort to the 'quick' method.

In case you missed it in the flurry of messages, they suspected this might be a problem, but did not have an 'extra' pulley lying around to give it a quick try (about the time I called you). But, others responded they did not think this could be it, so we kinda move on from there. *HOWEVER*, late last week they did quick test with this pulley off (of course all the belts off too) and cranked her up quickly and said the vibration was still there. But, I sort of have to wonder whether this is really a valid test or not (supposed to be a vibration dampener: with it gone, shouldn't it maybe vibrate even more?). Don't know.
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With the crank pully off it should vibrate worse,but not always under a no-load scenario-ie-driving.I have run way too many engines without a balancer in static mode,and not noticed any vibration.Load test is the best,but not possible in most applications."ran a few of my derby engines under load-DON'T ASK :roll: "
if they were doing tranny work why were they taking off the pully in the first place? and you tell them if they broke it they replace it. none of this oh well it works fine it's not broken business. and i'd recommend finding a new mechanic.
Well, while the tranny was being rebuilt in TX, I had them do a few other odds and ends such as a new timing belt, water pump, and front oil seal. That's when the pulley had to come off.

As for this local Toyoto dealer yeah, I've not been real pleased over the years with local Toyoto service. One of the dealers was, at one time, very good with their service and I trusted them totally (and they did great work). But, their quality REALLY suffered in later years and I stopped going to them. This other dealer is fair, but I only use them when I just have to. I had no facilities of my own to drop a tranny, so I took it to them to do that (not to do the re-build; I sent it to Jeff Watson in TX for that work). At this point now however, I will find some way to do ALL my own work in the future, even if I have to rent some garage space or such.
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A couple of things come to mind here on this vibration issue. First off, the harmonic balancer/crank pulley assy. itself is balanced at the factory after the part is made. If I recall correctly, I believe their are drilled areas on the back face of the pulley, and possibly on the front face as well??? Those drilled areas are there as a result of the balancing process. Now, depending on where the broken off piece is missing on the back face of the pulley in relation to the area where the drilled spots are located is going to affect how much vibration will be caused by the damaged pulley. Also, if enough leverage was used to pry the pulley off the crank, the person using the pry bar may have bent the snout on the crankshaft. :roll: Have your mechanic check the runout on the crank snout with a dial gauge to see if the crank snout is bent. Last but not least, what about the flywheel. Did the shop mechanics remove the flywheel?? Did they resurface the flywheel, install a different flywheel, or did they just leave it alone and not mess with it?
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Well, the flywheel was removed and resurfaced when the clutch and clutch disc were replaced when the rebuilt tranny was installed. All those items have been RE-re-installed/inspected and checked out ok (according to them). I cannot really imagine a resurface job on a flywheel being *so* bad as to cause this vibration; seems like imperfections of that magnitude would be easily noticeable.

We have a new pulley on the way and should be here by Monday or so and they are gonna install it and we'll see what happens. Hopefully, this will do the trick.

BTW, I don't recall having seen any drilled holes on my current pulley for 'balancing' purposes. Is this a common practice? I would assume they were all made the same, but I'm not sure.
The flywheel should be okay as long as it was bolted back onto the crank properly.
The crank pulley may or may not have any drilled areas on the back face. Maybe some of the crank pulley assys. do and some don't?? I honestly don't know for sure. Maybe someone else can varify this?? The drilled areas aren't actually drilled clear through. A small amount of metal is removed in different areas around the circumference of the back face on the pulley with the tip of a large drill bit. Don't forget to check and see if the crank snout is bent.
Me again....hey i went in to get my auto checked for a minor prob......while i was there i spoke with the boss man and told him of your prob, he said if there was no vibration before then its something the to do with the trans, if it was them they would replace all the cluthch and the spigot type bearing, if this didnt work he recons its out with the box and in with another, he recons that even a reconed box can be a pain if when its done they dont notice a very mild bend or twist in a shaft or other part, cause if there is somthing like that it will cause a vibration. Remember they only replace what they can see needs it plus fit all new seals n bearings, I recon he's right, it needs to be checked out.

Hope these comments help.
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