Top End Knocking/Rattling - Possible Problems?

[DiggsNWT]

Hello all. I am looking to join the family of Nissan owners in the near future by picking up a very sweet 95 240SX LE (Blue) 5M.

The ride is currently parked. The owner thinks that the engine is blown. The engine does start fairly easily even after sitting for months. However, there is a serious knocking or rattling sound that definitely seems to be coming from under the valve cover. The engine does not seem to miss or run roughly even with revving the engine. It does not smoke white/black or blue. The knock/rattle conintues throughout rpm range. It almost seems like there is something loose in there rattling around

All fluid levels appear to be good.

Any ideas on what the problem may be?

DiggsNWT

[Jiggyfry]

It very well sounds like its the front timing chain guides. The KA has 2 timing chain guides that will make a hella-racket if not removed. Tell the owner the engine is screwed and lo ball him, LMAO. Theres an awsome write up on here too on how to remove the guides.

[DiggsNWT]

The owner explains that the sound started out as just being a slight rattle and progressed to the point where it now makes a seriously loud rattling sound. However, he says it still has all of its power.

I had read on nicoclub that the chain guides are a known problem...but could they make such a terrible racket?? Perhaps a piece broke off??

The owner is asking $4k but I think $3k would be fair...if I do not need a whole new topend.

DiggsNWT

[BadMojo]

I had read on nicoclub that the chain guides are a known problem...but could they make such a terrible racket?? Perhaps a piece broke off??

It's possible. It's also possible that the chain is really loose and starting to knaw its way through the front cover, which contains the water pump assembly. People have had the chain cut through water passages like a chainsaw.

If the chain had skipped a sprocket or two, you would probably notice some problems with driveability. If it really jumped or broke, you'd certainly notice a head full of bent valves.

Personally, I'd feel more comfortable buying the car after doing a compression test. If there's no damage now, there will be soon. When the chain gets really loud, bad stuff's about to happen.

$3000-$4000 seems like a lot for a car with possible engine problems that's been sitting for months.

[DiggsNWT]

OK...good info. I am going to pull it into our shop and do a compression test and pull the valve cover off (will this screw the valve cover gasket??) and check it out what is happening under there. Of course, the seller would have to allow me to do this.

The $3-4k is Canadian.

Diggs

[BadMojo]

OK...good info. I am going to pull it into our shop and do a compression test and pull the valve cover off (will this screw the valve cover gasket??) and check it out what is happening under there. Of course, the seller would have to allow me to do this.

The valve cover gaskets (there's two, one around the spark plug wells and another around the outside of the of the valve cover) will probably survive, depending on how old they are.

I've already reused them, but these were fairly new gaskets. Careful with the valve cover bolts...it's REALLY easy to strip those holes. Unfortunately, I don't have the torque specs handy.

[Jiggyfry]

YES! hello Canada! Where you at in Canada?

And listen to Badmojo, the cover bolts strip really easy, ask me how i know. If you do take off the valve cover might as well remove the upper timing chain guide as it will be right in your face. Both of mine were rattling like crazy, now everything is back to normal. If the seller doesnt know squat aboot cars then tell him theres some serious stuff wrong and bargain more with him, maybe youll get it super cheap. Good luck bud-dy.

[DiggsNWT]

Western Canada...

So lets say there is damage in the top end...what would I likely be looking at for parts/$$$?

If things look interesting under the valve cover, I will post up a few pics.

Diggs

[DiggsNWT]

OK...I got this unit over to the shop today and attempted to remove the valve cover. The bolt in the top of the cover between cylinders 2&3 will not come out and the bolt head wants to strip. I aborted not wanting to strip the damn thing.

However, driving it I noted that at times the rattling noise stops completely. Left hand turns especially. Right hand turns and the rattle gets absolutely BRUTAL!! While idling, the rattle comes and goes. When the air conditioning compressor kicks in at idle, the engine lets off a rattle.

I tried the screw driver to the engine listening bit but could not exactly place the noise.

I wish I could get this problem diagnosed...I fell in love driving the car!!

I did take a short video with sound of the engine being revved...would it be helpful to post it somewhere??

Diggs

[Jiggyfry]

Still sounds like the timing chain guides, my noise would go away sometimes too, but not for too long. As for $, well you just remove the guides and do not replace them, they are useless. Free. That stuck bolt in the valve cover is gonna have to come out sooner or later, maybe tell the guy you want him to get it loose first so you can see inside. Look for the sticky on how to remove the guides so you can see the pics of them. Also check the tensioner to see if its seized, all this is explained in the sticky. And as for the video, if u can post it go for it, the more info the better.