Alfa Romeo Forums banner

1 - 20 of 40 Posts

·
Registered
Joined
·
183 Posts
Discussion Starter #1
So I'd like to get my grossly inaccurate mechanical tach working. If I spin the cable, the needle moves. Yay. If I run the engine, the stub sticking out of the water pump doesn't move. Boo.

I assume there's some sort of gear drive in there. If I remove the two 10mm bolts:

1. Will I find a user-serviceable and perhaps replaceable part that can be pulled out?

2. Will my car pee motor oil and/or coolant all over the garage floor?

3. Is there any point in working on the driver itself, or is the problem more likely in the water pump?
 

·
Super Moderator
Joined
·
11,585 Posts
The problem is most likely that the worm gear that is supposed to stick out of the end of the intermediate sprocket is absent (from an electric tach engine) or has come loose (unlikely).
The bronze tach drive itself is very simple. One gear machined as part of a hardened shaft, with an oil seal pressed into the bronze carrier, held in place by 2, 6 mm bolts with a gasket between the drive assembly and water pump. If you can remove it without removing the water pump, the worm gear drive from the intermediate sprocket is loose or absent. Yes it will leak oil, not a lot. Nothing pressurized there. No coolant. The provlem is nost likely NOT the water pump. Intermediate sprocket (race) with worm gear in place pictured below.
 

Attachments

·
Registered
Joined
·
183 Posts
Discussion Starter #3
Thanks Gordon.

There is a stub sticking out where the cable attaches, but it spins freely in its housing. I'll pull the driver housing from the pump and see what's going on inside.
 

·
Super Moderator
Joined
·
11,585 Posts
If the drive from the intermediate sprocket worm gear is attached to the sprocket, you may have difficulty pulling the drive assembly as the gears will be in contact at about right angles. Give it a try.
 

·
Super Moderator
Joined
·
10,629 Posts
1. Will I find a user-serviceable and perhaps replaceable part that can be pulled out?

2. Will my car pee motor oil and/or coolant all over the garage floor?

3. Is there any point in working on the driver itself, or is the problem more likely in the water pump?
Not to dispute anything Gordon wrote. But yes, you can remove those two 10mm bolts, and remove the tach drive. If Gordon says it may stick, I wouldn't question that. Though removing the whole waterpump-tach drive assembly is never a problem. The point is, it won't "pee motor oil and/or coolant all over the garage floor". (Of course, that begs the question: "what kind of an Alfa owner doesn't already have motor oil and/or coolant all over his garage floor?)

Keep in mind that when you remove the two 10mm bolts you will disturb the position of your ignition timing pointer.

I don't think those tach drives are available new. When you get a new water pump, you just transfer your old one onto the new pump.

The waterpump just holds the tach drive against the gear that comes out of the intermediate chain sprocket. So replacing a worn waterpump won't help you if one of those gears is worn/broken. But taking out the tach drive may enable you to inspect the two gears and diagnose the problem. If the problem is the removable drive, someone on the BB will have a spare. If it's the intermediate chain sprocket....well, having a working tachometer is greatly overrated.
 

·
Super Moderator
Joined
·
11,585 Posts
Actually Jay, I've installed a worm gear in that sprocket on an engine that had a replaced electric sprocket once I removed the radiator water-pump and everything up front preparing to pull the engine, to remove the head, sump AND then front cover to get at the sprocket. I had a spare worm gear, and tapped it in with a brass hammer. It actually worked, to my amazement! Now as to removing the worm gear, engine assembled, I was not as lucky. I did the same disassembly as above, grabbed the gear woth a correctly fitting TIGHT collet, and went at it with a slide hammer (a small one).
Ruined the collet, and the gear, and had to pull the engine apart. Pooh. It's always something in Alfa land!
 

·
Super Moderator
Joined
·
10,629 Posts
If the drive from the intermediate sprocket worm gear is attached to the sprocket, you may have difficulty pulling the drive assembly as the gears will be in contact at about right angles.
Now you have me a bit confused. Are you saying that Cheburashka may have difficulty:

- Pulling out the tach drive, the thing secured to the water pump with the two 6mm bolts? I must admit, I don't see why that wouldn't just roll off the worm gear.

- Pulling the cylindrical worm gear out of the intermediate sprocket gear?

At first I thought you meant the former, but now I think you mean the latter.
 

·
Super Moderator
Joined
·
11,585 Posts
Hi Jay,
Sometimes the bronze body sticks in the pump housing. There are tricks required to free it without marking it up. Other times, the tach drive gear does not want to roll off the worm gear and pulls out of the housing. Rotating the engine by hand usually frees it.
Pulling the cylindrical worm gear from the intermediate sprocket with engine assembled, WAS a PITA the one time I tried it. (Read FAIL) Reinstalling the cylindrical worm gear in the sprocket, water pump off, engine assembled, in the car, was simple, the one time I tried it given room to work.
My discussion of mechanical labors, can be confusing. I write it as I did or tried to do it. When I read it over, I think "Yup, that's what I did." though the discussion may be impossible to figure out unless you watched me. You know well how that goes!
 

·
Super Moderator
Joined
·
10,629 Posts
My discussion of mechanical labors, can be confusing. I write it as I did or tried to do it. When I read it over, I think "Yup, that's what I did." though the discussion may be impossible to figure out unless you watched me. You know well how that goes!
Yup. Often it's hard to express this stuff in words. I often think to myself: "boy, if that guy and his car, were in my garage, I could explain it (and sometimes diagnose it) in 30 seconds". But trying to write out an explanation - blah!
 

·
Super Moderator
Joined
·
11,585 Posts
You got that 100% Jay. Even some simple things like balancing Webers without anything but a screwdriver, is a matter of experience. Trying to explain it is a completely different thing.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #11
Can an electronic tach from a later car be fitted? Would it look similar to the existing gauges? What year did Alfa go from mechanical to electronic?
 

·
Super Moderator
Joined
·
11,585 Posts
Yes and no. The early electronic tachs were distributor activated ( I believe {I only work on earlier cars so I need to be corrected here}). The mechanical tach cars used Veglia guages, with Giulia style faces. By 77 the electronic guages featured different faces.
The above is my guess from memory of newer cars only, and may be incorrect. We need better confirmation.
 

·
Registered
Joined
·
8,111 Posts
Thanks Gordon.

There is a stub sticking out where the cable attaches, but it spins freely in its housing. I'll pull the driver housing from the pump and see what's going on inside.
have you confirmed if the drive gear is actually there?
if you are lucky enough to have the little gear drive inside, it ought to look something like this in the 1st photo here (just so you have an idea!):

http://www.alfabb.com/bb/forums/1042305-post1.html
 

·
Registered
Joined
·
183 Posts
Discussion Starter #14
I was doing fine until I hit this:



I understand the function of a hex-head bolt. I don't understand how one can get tightened down when one of its faces is in direct contact with a solid metal object. I can see how this could have been installed when the water pump wasn't on the car, but now I don't see how I can remove this without grinding a six-point socket down to four faces, leaving two open at the lowermost point where the pump body is in the way. That's probably where I'm headed at this point. I'd really rather not pull the water pump.
 

·
Super Moderator
Joined
·
11,585 Posts
There is a "crow foot wrench" that will fit between the threaded stub and will grab three sides of the nut, allowing you to turn it 1/6 turn at a time. The one I have is 1/4 inch drive 10 mm and has the drive above the hex. I use it once every 500 years or so. Once you crack the bolt loose, you can turn it out (ha) with finger pressure according to the "instructions". Then cut a screwdriver slot in the bolt hex head for re-installation.
I have a bigger one used for Ferrari tranxaxle filler hole plugs, 22 mm x 1/2 inch drive. Use that one 2ce a year. (Unless some idiot saftety wired the plug while the transaxle was OUT of the car). Then the cars owner gets an extra $50.00 "stupid fee" added to his bill. No normal human hand is small enough to reach up in there with miniature side cutters and cut the wire out. I have to hire some child about 8 years old with some degree of mechanical understanding and ability to use tools, OR pull the transaxle for $500.
Many Italian cars have similar features.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #16 (Edited)
Progress. Well, sometimes progress means adding three more hours to a ten minute project.

With the water pump in place, the driver wouldn't budge. Really. Lots of persuasion, and nothing worked. So off came the radiator, fan, fan belt, alternator, and water pump mounting bolts. Once the water pump was free of the block, the driver came out slick as you please. I haven't pulled the front pulley and would prefer not to since the water pump is doing its job and has no play in it.

The driver looks great to me.



I'm not sure what's supposed to be behind the water pump, but this doesn't look quite right to me:



I know it's not the best picture, but is that right? If it is, and I have both worm gears and I can verify a solid connection between the driver worm gear and the square-holed output shaft, why wouldn't I be getting any rotation?

Crazy idea here, but I noticed that I don't have a pointer on mine. Is it possible that the lack of a pointer changes the interface between the two helical gears, leading to my particular problem?
 

·
Super Moderator
Joined
·
11,585 Posts
Does the worm gear turn when you turn the engine? Can you stop it turning with long nose pliers? If not, THATS GOOD. Next, have you pulled the gear out of the housing? Is the gear and shaft in one piece? I would assume it's not broken. Then when the worm gear rotates, does it have broken teeth? (I've never seen that other than the one I ruined trying to pull it with a slide hammer.) If both gears are intact, and the worm gear turns with the engine, the tach drive should turn with the engine. If it does not, the gear teeth are not engauged with one another, but that cannot happen as the bore hole for the tach drive locates the gears so they must engauge with one another.
Below is a picture of a 750/101 water pump recentl rebuilt. Note the location of the tach drive in the pump body. The hole for the worm gear is located to match the hole in the front cover. They line up. If the pump body has not been somehow modified, allowing extra lateral clearance so the worm gear cannot contact the tach drive gear, it should work, UNLESS, as mentioned, the worm gear is not a tight fit in it's bore in the intermediate sprocket, or somehow, the stud end that is pressed into the intermediate sprocket gear bore hole has broken. If it has broken or is not pressed in, you will be able to turn the worm gear without turning the engine. (thats BAD!).
 

Attachments

·
Registered
Joined
·
183 Posts
Discussion Starter #18
So it looks like I have to bite the bullet and buy the 38mm socket for the front pulley. Otherwise, I have very limited access to the worm gear on the front of the engine. I've looked and it seems odd to me that the steel gear runs directly on the aluminum body. Is there supposed to be a thrust washer in there?
 

·
Super Moderator
Joined
·
11,585 Posts
No. The bodies used to be bronze. (previous pictures).There is no thrust gear loading. Are you sure you can't get a long nose in there to try turning the worm gear?
Problem is, if its broken off, you cannot get the stud out of the intermediate sprocket without a hydraulic press. The sprocket shaft is hollow and maybe a correctly fitting drift and hammer would remove it, but I just use a press. To do that, you need to pull the engine, remove the head, sump and front cover. Remove the intermediate sprocket and crank sprocket, and then have at it. Hours of labor. PITA. At least you are doing it and not me. That's comforting!
 

·
Registered
Joined
·
183 Posts
Discussion Starter #20
I checked with long-nose pliers. It won't turn on its own and it does turn with the engine. I guess that's a good sign. So I have a working worm gear on the engine, the same on the pump, and yet no movement of the cable.

I think pulling the water pump is a must--especially since I buggered up the sealing surface between the pump and the driver and I need to smooth things out. I think once the pump is off of the engine, I can get a better sense of where that gear sits once the driver is installed in the pump.
 
1 - 20 of 40 Posts
Top