chain tensioner install
12-06-2003, 12:44 AM
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chain tensioner install
How far out should the tensioner piston be extended when pressure fed tensioners are installed on a newly rebuilt motor?
I just completed timing the cams on a fresh rebuild, and it doesn't seem like the tensioner is fully extended. My assumption is that this will change as soon as the oil pump supplies hydraulic pressure to the system, and what I am seeing now (piston extended about 6mm above tensioner body) is only the force from the spring.
Any comments would help me sleep better.
Thanks,
Ian
I just completed timing the cams on a fresh rebuild, and it doesn't seem like the tensioner is fully extended. My assumption is that this will change as soon as the oil pump supplies hydraulic pressure to the system, and what I am seeing now (piston extended about 6mm above tensioner body) is only the force from the spring.
Any comments would help me sleep better.
Thanks,
Ian
12-06-2003, 01:43 AM
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I don't think oil pressure extends the piston at all. The function of the oil is to provide damping for the spring action.
Once you pull the holding pin from the tensioner, the piston should spring out and apply full tension to the chain.
Once you pull the holding pin from the tensioner, the piston should spring out and apply full tension to the chain.
12-06-2003, 10:05 AM
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Once you pull the holding pin from the tensioner, the piston should spring out and apply full tension to the chain.
12-06-2003, 12:26 PM
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Respectfully, I question this "priming" advice.
The only way you could actually (manually) prime a Carrera tensioner, would be to submerge it in oil.....while pumping the piston, in and out. If you have bionic fingers like a vise, you may be able to do it. Even a large pair of channel-lock pliers will have difficulty with that piston. And you could damage the machined face of the piston.
I'd suggest this more practical method, which I have done several times myself when installing Carrera (pressure-fed) tensioners.....
1) After tensioners are installed, pull the fuel pump relay, and disable the CDI by pulling the connector at it's base.
2) Key the starter, and crank for 10 seconds. Repeat 5-10 times, allowing the starter to rest for a minute or two between sessions.
3) Replace the pump relay, and CDI plug.
When you fire the engine, the tensioners should be doing their job.
As Bill mentions, there have been rumours of tensioners failing from new. I say 'rumours', because all the ones I have installed have functioned perfectly. They may rattle for a few seconds after start-up, especially if you neglect to build up pressure as I described here. If the rattle does not cease shortly, you should make sure all the oil lines and fittings are correctly installed. And don't forget to pull the 'grenade' pins before you button-up the covers.
The only way you could actually (manually) prime a Carrera tensioner, would be to submerge it in oil.....while pumping the piston, in and out. If you have bionic fingers like a vise, you may be able to do it. Even a large pair of channel-lock pliers will have difficulty with that piston. And you could damage the machined face of the piston.
I'd suggest this more practical method, which I have done several times myself when installing Carrera (pressure-fed) tensioners.....
1) After tensioners are installed, pull the fuel pump relay, and disable the CDI by pulling the connector at it's base.
2) Key the starter, and crank for 10 seconds. Repeat 5-10 times, allowing the starter to rest for a minute or two between sessions.
3) Replace the pump relay, and CDI plug.
When you fire the engine, the tensioners should be doing their job.
As Bill mentions, there have been rumours of tensioners failing from new. I say 'rumours', because all the ones I have installed have functioned perfectly. They may rattle for a few seconds after start-up, especially if you neglect to build up pressure as I described here. If the rattle does not cease shortly, you should make sure all the oil lines and fittings are correctly installed. And don't forget to pull the 'grenade' pins before you button-up the covers.
12-06-2003, 05:55 PM
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Thanks guys,
A few extra questions though:
Does the hydraulic pressure assist the lift, or only provide damping to the spring? How do the later tensioners differ from the early versions prone to failure?
Anyone use the safety collars on the smaller diameter of the tensioner piston, or should I just pass on those because they are kind of hokey?
Ian
'83 SC Euro
A few extra questions though:
Does the hydraulic pressure assist the lift, or only provide damping to the spring? How do the later tensioners differ from the early versions prone to failure?
Anyone use the safety collars on the smaller diameter of the tensioner piston, or should I just pass on those because they are kind of hokey?
Ian
'83 SC Euro
12-06-2003, 06:47 PM
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The hydraulic pressure does not assist the lift. The pressure is practically the same on both sides of the internal piston. The deal is that the piston comes out easy, because the internal oil passage is huge for that motion while the oil passage is very small to compress the tensioner, making that motion very slow and 'hard'.
The later tensioners differ mainly by feeding the hydraulic fluid from the engine oil supply. They can still fail, once the seals are old. The older tensioners would fail immediately once the seals were bad, because the hydraulic fluid wasn't replenished.
The main reason the old tensioner setup had problems was also the narrow idler arm sprocket base. In 81 they went to a wider base which fixed the problem.
The safety collars are made for the non pressure fed tensioners. To get the same effect on a pressure fed tensioner, you need to take it apart and put a shim in the very bottom. This will avoid total collapse of the tensioner (wich still happens on the oil fed ones). The shim can be made from brass piping and needs to be thick enough to take up the slack but thin enough to allow enough travel. Basically, you have to follow the same procedure as you would do to install the collars in the right location on the older setup.
HTH,George
The later tensioners differ mainly by feeding the hydraulic fluid from the engine oil supply. They can still fail, once the seals are old. The older tensioners would fail immediately once the seals were bad, because the hydraulic fluid wasn't replenished.
The main reason the old tensioner setup had problems was also the narrow idler arm sprocket base. In 81 they went to a wider base which fixed the problem.
The safety collars are made for the non pressure fed tensioners. To get the same effect on a pressure fed tensioner, you need to take it apart and put a shim in the very bottom. This will avoid total collapse of the tensioner (wich still happens on the oil fed ones). The shim can be made from brass piping and needs to be thick enough to take up the slack but thin enough to allow enough travel. Basically, you have to follow the same procedure as you would do to install the collars in the right location on the older setup.
HTH,George
12-06-2003, 07:02 PM
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As Bill mentions, there have been rumours of tensioners failing from new.
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12-06-2003, 08:44 PM
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Sorry if this sounds repetitive, but I am very concerned about the potential failure of a tensioner. If the oil pressure does not assist in the lift, but rather (severely) damps the piston response, how would old seals in a newer style tensioner result in failure of the system? Doesn't the spring have enough force to maintain tension at least for a short time until you can power down if there is no hydraulic pressure or flow?
