Alfa Romeo Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter #1 (Edited)
Do these photos show rear bank out by one tooth? (1990 164 12-valve 3.0 V6 - non-US)

How do I detension the belt to correct this? Belt is only 1/3rd through its lifespan so would rather not replace but would welcome opinions on this. Suspect may have been installed incorrectly rather than skipped.

Crank at TDC


Front bank scribed mark lines up with template


Rear bank scribed mark off by one tooth?


Tensioner
 

·
But Mad North-Northwest
Joined
·
10,475 Posts
I see a decent amount of oil on your belt and the pulleys. If that's the case you should replace the belt and fix the oil leaks: oil will cause early belt failure.
 

·
Registered
Joined
·
8,780 Posts
Don't use the timing mark on the flywheel as shown in the manual. Just line it up per your pics. The mark on the flywheel is incorrect.
Instead of the special tool, use a screw driver, or pin that fits.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #6
Thanks guys. The oil and grease visible is from a couple of recent events (split CV boot and oil filter not properly tightened), and will be fully cleaned up and monitored for any continuing leaks.

I will be replacing the cambelt in the reasonably near future but would like to correct the timing in the meantime. Access isn't too bad so I don't mind going in there twice.

Thanks for the directions Richard2, will be sorting this out in the morning. Only planned to do the aux belts and replace the split CV boot, but am now very glad that I decided to check the cam timing "while I was in there".
 

·
Registered
Joined
·
2,218 Posts
Jbg, the "stepped" factory detensioner pin is quite important (post #4, second picture). You can make one, here is Fred di Matteo's description:

The factory
tool has two dimensions at the end to insert through two holes. I can't
draw the tool on this letter but the dimensions are 0.190" on the very
end by 5/8" long and 0.27" at the rest of the rod. We make them from a
2 inch long bolt stripped of all the threads, machine the bolt to 0.27"
diam. one inch from the head. The end 5/8 inches are machined to 0.19".

——————————— 0.19" x 5/8"
0.27" ———————
x 1" ———————
 

·
Registered
Joined
·
4,049 Posts
If your going in there to correct the timing, you may as well replace the belt, no matter the age or mileage of it, especially if it is oil covered it's due no matter. ~5 hours labor, you don't want to go back in there. It may look easy, but it isn't. Get one on hand and I guarantee you, once you go in that far you will want to put it on. Do inspect cam seals and consider doing that as well. You have a T/B tensioner rebuild kit? There is no way that is CV grease or oil filter oil. Oil filter oil will not come around to the front like that, it would run down the back. This stuff quickly snowballs, unfortunately, but that is the natural of the beast.
Charles
 

·
Premium Member
Joined
·
15,842 Posts
Where in NZ are you located? If in the North Island, there is a good Alfa/Fiat shop in Cambridge.
 

·
Registered
Joined
·
8,780 Posts
If you can wait until next month, maybe I can help you with it:) We're in NZ from Nov 28 to Jan 28.
This is not a NA version, so It may be easier. I'm not sure if the timing is different or not. I suspect not, but don't know. If the timing is the same The template works really well, no need to use the marks on the cams.
 

·
Richard Jemison
Joined
·
7,370 Posts
Cam timing

The template works really well, no need to use the marks on the cams.
Really? There is enough slop in the sprocket assemblies to alter timing a few degrees. I suppose that`s why the timing marks are on the cam and cam caps.
 

·
Registered
Joined
·
2,218 Posts
Jbg, was the engine running roughly with the belt in that position, or is this a new install on a static engine and you're just concerned before firing it up? (Belt skipping with oil-fed detensioner is sort of uncommon unless the tab that moves the actuator is broken off).
 

·
Registered
Joined
·
21 Posts
Discussion Starter #15
If your going in there to correct the timing, you may as well replace the belt, no matter the age or mileage of it, especially if it is oil covered it's due no matter. ~5 hours labor, you don't want to go back in there. It may look easy, but it isn't. Get one on hand and I guarantee you, once you go in that far you will want to put it on. Do inspect cam seals and consider doing that as well. You have a T/B tensioner rebuild kit? There is no way that is CV grease or oil filter oil. Oil filter oil will not come around to the front like that, it would run down the back. This stuff quickly snowballs, unfortunately, but that is the natural of the beast.
Charles
I’ve ordered a timing belt and tensioner rebuild kit and will carry this work out soon; however, I need the car working and was not comfortable continuing to drive it with the timing out while I waited for parts to arrive (since a slip of one tooth could cause valves to contact pistons -- as unlikely as slippage is with the hydraulic tensioner that's still a bit scary!).

So, today I corrected the timing using the existing T/B and tensioner. It only took a couple of hours so I don't mind doing it again soon (along with the extra work to rebuild the tensioner).

Really? There is enough slop in the sprocket assemblies to alter timing a few degrees. I suppose that`s why the timing marks are on the cam and cam caps.
I really can't see how there is that much slop in the sprocket assemblies. It would have to be enough slop to equate to at least a tooth on the belt, and I just can't see where that slop would come from.

Jbg, was the engine running roughly with the belt in that position, or is this a new install on a static engine and you're just concerned before firing it up? (Belt skipping with oil-fed detensioner is sort of uncommon unless the tab that moves the actuator is broken off).
I just happened to check the timing while I was doing other belts. The engine seemed to be running fine to me, but now that I've corrected the timing it has noticeably better performance. It's never been this good, so I suspect it has been a tooth off since I got it (I had a T/B change and tensioner overhaul done by a reputable, Alfa-knowledgeable mechanic just before I took delivery of the car).

If the tab that moves the actuator is broken off (it isn't broken on mine), wouldn't it never detension the belt, and therefore the belt would be less likely to skip? (But more likely to wear out bearings etc quickly.) Honest question, just trying to further my understanding of the detensioner.
 

·
Registered
Joined
·
2,218 Posts
Many thanks for your thorough report—it sounds like you are all set and have diagnosed the problem correctly.

Here's the explanation for your last question, the tab. The springs do the tensioning on a running engine, and as thermal expansion occurs, the springs just allow the detensioner to adapt, i.e., maintain the same tension. But when starting a cold car, that's where the tab comes into play. Here the spring of the plunger pushes the actuator rod against the tab, putting EXTRA tension on the belt, adding to the tension of the springs. Only at startup when TB skip is most critical. Then when the engine starts, oil pressure from the engine fills the cavity where the plunger resides, pushes the plunger out of the way, and the shaft pulls off of the tab allowing the springs to do their tensioning unassisted. Here's a pdf with a more thorough explanation of this ingenious device.
 

Attachments

·
Richard Jemison
Joined
·
7,370 Posts
slop

Take the entire assembly loose and you cand find plenty of clearance to make small adjustments. The keyway it`s self is loose. What grabs and holds the cam in fixed position is the taper not the key. Once the taper is loosened you can set the cam.
 
1 - 17 of 17 Posts
Top