jeeprider Posted August 29, 2017 Report Share Posted August 29, 2017 A friend of mine has a 1984 Nissan 720 2.4L 2WD. Blew the head gasket between cylinder 3 & 4. We read the Haynes service manual, and it made it sounds easy, but we can't do anything at all. The cam chain is insanely tight. How do we get the chain to be loose so we can take the cam sprocket off? We've been trying for 2 days. We are out of all ideas. Quote Link to comment
datzenmike Posted August 29, 2017 Report Share Posted August 29, 2017 First.... do you have the chain blocked so that the timing chain tensioner cannot fall out???? The chain is kept 'tight' by a spring loaded tensioner. It is imperative that the chain be secured so that the tensioner not fall out or the entire front of the engine must be removed to get at fix this. This will add a day's work to your job and is preventable. If you don't know about this FIND OUT how. You can buy or make a device to hold the tensioner in place. Assuming the engine is at TDC, the chain secured and the chain and sprocket marked so you can put the chain and sprocket back in the same position.... the procedure is to loosen and remove the cam sprocket bolt and tap the sprocket forward and off off the front of the cam. 1 Quote Link to comment
Doctor510 Posted August 29, 2017 Report Share Posted August 29, 2017 Tacky question, you did remove the bolt that holds the gear on, RIGHT? Quote Link to comment
jeeprider Posted August 30, 2017 Author Report Share Posted August 30, 2017 Tacky question, you did remove the bolt that holds the gear on, RIGHT? Yes we did. We could just hit the sprocket off with a rubber mallet, but them how would we get it back on? That chain is ridiculously tight. Quote Link to comment
jeeprider Posted August 30, 2017 Author Report Share Posted August 30, 2017 First.... do you have the chain blocked so that the timing chain tensioner cannot fall out???? The chain is kept 'tight' by a spring loaded tensioner. It is imperative that the chain be secured so that the tensioner not fall out or the entire front of the engine must be removed to get at fix this. This will add a day's work to your job and is preventable. If you don't know about this FIND OUT how. You can buy or make a device to hold the tensioner in place. Assuming the engine is at TDC, the chain secured and the chain and sprocket marked so you can put the chain and sprocket back in the same position.... the procedure is to loosen and remove the cam sprocket bolt and tap the sprocket forward and off off the front of the cam. We made the wooden piece to hold the chain and tensioner. So, we just simply hit the sprocket off the camshaft, even though the chain is super tight? How do we get it back on after were done? That chain is hard to fight. We've been following the haynes service manual, but the tight cam chain got us. Quote Link to comment
Stoffregen Motorsports Posted August 30, 2017 Report Share Posted August 30, 2017 Sounds like maybe the tensioner plunger is already out and causing the chain to be tight. I've seen it many times where the plunger pops out and gets jammed between the chain and the tensioner block. You should be able to look down inside the cover to see the plunger. If it is popped out, then you've got to remove the front cover to fix it, which will probably mean a whole new timing set. If it's not popped out, then you've got another problem, which means probably pulling the front cover to fix. So either way, it sounds like you've got to pull the cover. I am not there to see this in person, but that's what it sounds like. 3 Quote Link to comment
Crashtd420 Posted August 30, 2017 Report Share Posted August 30, 2017 Sorry to say but the only way to be certain is to pull the timing cover.... Your friend may have an issue with the tensioner? Or something... Could the tensioner have popped out Because the cam chain was extremely worn? I don't know how tight super tight is... Maybe pop the sprocket, since you have the wood wedge in place and see if you can get the sprocket and chain back on without problems... If so continue on.... if not you ll wanna pull the timing cover and dig deeper, if your gut is telling you something may be wrong I would listen... better safe then sorry and doing things multiple times.... 2 Quote Link to comment
Crashtd420 Posted August 30, 2017 Report Share Posted August 30, 2017 Well i guess stroffgren types faster than me.... 1 Quote Link to comment
jeeprider Posted August 30, 2017 Author Report Share Posted August 30, 2017 Sounds like maybe the tensioner plunger is already out and causing the chain to be tight. I've seen it many times where the plunger pops out and gets jammed between the chain and the tensioner block. You should be able to look down inside the cover to see the plunger. If it is popped out, then you've got to remove the front cover to fix it, which will probably mean a whole new timing set. If it's not popped out, then you've got another problem, which means probably pulling the front cover to fix. So either way, it sounds like you've got to pull the cover. I am not there to see this in person, but that's what it sounds like. I'm new to this stuff, so i'm not entirely sure what you mean. If I got pictures of what i'm dealing with, would it help? 1 Quote Link to comment
banzai510(hainz) Posted August 30, 2017 Report Share Posted August 30, 2017 send photos Did you use a chain wedge to keep tha chain tigh so the tensioner dont pop out? if yes then your OK. If not and your really have alot off travel to pull up the chaain to get even close to the dowel on sprocket then your fucked. If you did use a wedge and jammed it down the front cover then you might be ok, just pull the sprocket up and maybe turn the cam clock wise to introduce slack on th tight side of chain and might geive you a 1/16 or 1/8 ich more up movement. there is a Zseries timming chain wedge. try amazon 1 Quote Link to comment
Crashtd420 Posted August 30, 2017 Report Share Posted August 30, 2017 Pics Always help.... the timing tensioner is just as it sounds.... spring loaded and keeps tension on the chain... If the chain became too lose the tensioner could pop out because it extends too far.... it located Inside timing cover... Quote Link to comment
Stoffregen Motorsports Posted August 30, 2017 Report Share Posted August 30, 2017 You just never know what has happened to these engines after a long life of service. My suggestion was based on running vehicles. I've seen running engines with the tensioner popped out, and apparently that way for a very long time, since there were grooves worn into the plunger by the chain. Look at the first image on this page. This is can happen on a running engine - https://www.google.com/search?q=datsun+timing+chain+tensioner&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjjkrmX2P_VAhXkiFQKHTR9DkUQ_AUICygC&biw=1680&bih=910#imgrc=sogDiBOTzoJtEM: This could have happened a while ago, so even if you did wedge the chain, as Hainz asked, it may have been damaged prior to the head gasket blowing. 1 Quote Link to comment
G-Duax Posted August 30, 2017 Report Share Posted August 30, 2017 This also points out the lack of detail in the Haynes & Clymer service manuals. When I buy a new car, I always hunt down either a new, or used factory service manual. 1 Quote Link to comment
datzenmike Posted August 31, 2017 Report Share Posted August 31, 2017 Someone on here mentioned taking a timing cover off a running engine and finding a wooden wedge (or what was left of it) still in there. You may still be OK. Continue on and see what happens when trying to get the sprocket back on. I had a tight one once. The sprocket would tilt slightly but the bolt would tighten in. I made sure the hole in the back fit the small dowel pin on the front of the cam and tightened it gradually. It pulled the sprocket up, tightening the chain, but it did go on. 1 Quote Link to comment
Stoffregen Motorsports Posted August 31, 2017 Report Share Posted August 31, 2017 But he's saying it's so tight that it's not coming off. That's tight. 1 Quote Link to comment
datzenmike Posted August 31, 2017 Report Share Posted August 31, 2017 Jamming a wedge down between the guides will also pull down on the chain and 'tighten it'. Probably fine, hope for the best. 1 Quote Link to comment
Stoffregen Motorsports Posted August 31, 2017 Report Share Posted August 31, 2017 So what you're saying is that the wedge he is using right now may be the cause of the tension on the chain. Let's hope so. Per your statement above, I found a screwdriver inside the front cover of a L18 once. It had been there for years. 1 Quote Link to comment
Cheetahking Posted August 31, 2017 Report Share Posted August 31, 2017 I agree - if the sprocket were intstalled - and the chain wedges didn't loosen, it should be fine. Two things - to get the sprocket back on - I find that having the cam dowel aligned was a bigger issue - which I was blaming on the chain being tight. Rotating the cam slightly while trying install the sprocket is helpful. You can lift up on the sprocket by running a 3/8" extension through the holes in the sprocket and over the tower and us the extension as a lever to help it into place. It will go on. Definitely try this and other things before removing timing cover (as along as wedge is still in place), Front cover is a lot more work that may not be necessary...... 1 Quote Link to comment
jeeprider Posted September 1, 2017 Author Report Share Posted September 1, 2017 Quick update. I forgot who said it, but someone mentioned using a extension for leverage. We put a extension through the cam gear and pulled up and it popped right off! You guys are heroes! Now, we are taking the front engine cover off anyway because it looks like the tensioner has popped out. Quote Link to comment
Lockleaf Posted September 1, 2017 Report Share Posted September 1, 2017 Look behind the oil pump for a hidden cover bolt. You have to remove the pump to get it Quote Link to comment
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