308 Alternator Belt Tension (A/C, H20 Belts too!)

Thanks for identifying it. I ordered both the tensioner and the Gates Pencil Gage
Guess I'll have to sip margaritas until Tuesday...

 

The tool from Ferguson will work great for the Alternator.
For the water pump and AC Compressor: I would use a fine tip marker to scribe a line on the tensioner adjustments for the water pump and AC compressor. I used my hand to apply the tension, tightened the nut to hold position, then measure deflection. If too tight or loose, then loosen adjuster nut slightly, move the adjuster very slightly in the correct direction , tighten, and check measurement. Then do it again, if not in spec.

 

I would use the Krikit tool too. Works fine on my Porsche and Ferrari.

 

I also like the Gates Krikit Tool for the A/C and Alternator Belts. But it will not fit properly for the H2O Belt on a 3-Belt car like mine.

 

Thanks for posting this! I have an 84 with the single belt for the water pump and alternator. My belt was squealing a little at low rpms. I finally bought the Gates krikit 91107 from Amazon for $11. Tension was definitely low.

I also bought the belt tension jack from Amazon because of this post. It made this job so easy! Thank you for letting me know about it. The tension is now properly set, and it is now quiet.

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I just dealt with this on my 328, figured I'd share my experience.

Re: the Krikit... Dayco has a training a video on using the Krikit. It's on Youtube. They claim it's highly accurate when used properly (ie; in a controlled lab setting). I suspect the main issue is it's not always possible to use it properly because you're elbows deep in a rat's nest of other belts, pulleys, cooling pipes, brackets etc. But, you do the best you can.

As far as getting tension on the Alt... I ended up carefully using a big wrench as a prybar with one hand to force the alt downwards, then cinched down the nut with the other hand (socket with a couple extensions and a U -joint). An actual prybar with some shop towels would probably be better if you have it. Just be careful and mindful not to go crazy in there as obviously you could damage something if you're not doing this thoughtfully. But common sense stuff.

The challenge at that point is the cinch-nut, which wants to spin around unless you have another wrench on the back side. So for that I just hung a long box end wrench from the backside nut and kinda wedged it against the frame so it wouldn't spin around. Mission accomplished, no big deal once I figured out the method. And for sure after I ran the motor for a few minutes all the acc'y belts had stretched a bit. So I had to re-tension them.

 

Great thread. I just replaced the WP/Alt belt which had burned up just after the squealing started. Some background:

I had a new A/C system (Vintage Air kit, works great!) installed by Denver Ferrari a while back. Of course, they had to move the WP belt in the process and it burned up within 15 miles of picking up the car. Back to the shop for a replacement which then lasted the trip home from Denver to Santa Fe (350 miles), then a few days later a round trip to the Mojave Desert (about 1400 miles) including a 23F morning in Flagstaff. No problem. Then it burned up on a 5 mile trip to the grocery store the day after I got home.

I set the tension on the new belt per this thread with a Krikit, seems to have worked great.

So my question is, how many miles until I need to recheck the tension? Do you guys recheck yours after replacing it and if so, at what mileage? Mine is set at 3kg right now per this thread, I'm figuring I'll recheck it at about 750 and set it at 2.5 kg per the owners manual. Yes?

 

This is what I have used, easy to use and works great.

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Nice! Did you make that or buy it?

 

https://www.ferguson.com/product/supco-belt-jack-instant-belt-tightener-sbj10/_/R-4479545?
View attachment 2577256

 

Also get this alternator bolt from Stage 8 as per this old thread. Brilliant solution for tightening this alternator tension nut.

https://www.ferrarichat.com/forum/threads/tightening-alternator-belt-made-easier.365828/

 

I bought it, they called it Belt Jack.

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Any guidance on how many miles to recheck the belt tension?

 

I have found that a new belt loosens up in about 5,000km, and needs to be retentioned to spec. It then seems to hold the tension for a long time after that.

Make sure you check the idler pully in the water pump belt, it is actually two small bearings in that pully., make sure it turns without any rough feel. Very easy to replace the bearings, there is an older thread on how to do this.

 

How much tension is it losing?

Which spec do you retension to: tension for a new belt, or a used belt? (As there are specs for both.)

 

My owners manual maintenance chart indicates to tension the belt after 1,000km on a new car, and 10,000 km therafter until 30,000 or 2 years.

The manual does indicate the tension spec on new and used belts, so that is what I tension do, on the new belt and then the old.

My experience is a new belt loses its tension in about 5,000km, and ends up about 10% low relative to the used tension belt spec at that time, which is about 10% less than the new belt spec.. So it does seem necessary to check the new belt for tension broadly within the first year of installing. But then I find the tension then stays put thereafter til I renew the belts, usually about 4 years for me, I put about 5,000km on the car per year, and it is climate control garaged. Frankly the belts always look fine when I change them, so it seems like overkill but that is the nature or prevenative maintenance.

My manual belt specs for CH 1988 Mondial 3.2 (average of the ranges) : Water pump 6.5lb new 4.5 used - measured with .15 inch delflection on the middle of the belt (i.e no tensiometer use is noted)
AC 47lb new, 41.5lb used, using a Gates tensiometer 150 (not longer available)
Alternator New 73.5lb, used 68lb using the Gates tensiometer

I use the krikit tool, seems to work fine and as I found it quite accurate on other cars I have played with I have no reason to expect it would not be similarly useful for the Ferrari. Absent a better guage or reproduction of the Gates 150, I am unaware of other practical choices to measure tension.

The reality is either your belts are flipping off and breaking if loose, usually you will get some belt slap and hear that if your belts are loose. Or your alternator and water pump bearings fail as you are overtensioning. 15 years of ownership and I have had no problems with any belts or bearings, so I am presuming I am in the range of correct tensions for the purposes intended.

 

Excellent, thanks for the guidance. This is what I was looking for.

 

Other than timing belts, I tighten my accessory belts just enough so that they do not squeal when the engine is first started when cold. No common metal expands more than aluminum when heated so belts tighten as engine warms.

 

What you guys think of this?

https://www.checkline.eu/prod/belt-tension-gauge/btm-400plus

an overkill but takes the dumb out of the equation

 

are these the same ?

 

I don't know that I'd pay $700 for a tool to replace a $20 Gates clicker gauge, to change a $18 belt every 5 years.

I sort of look at it this way: for decades, billions of belts were replaced without needing a laser/frequency device - and those belts were just fine. I'm not saying there's never a good reason to replace old tech with new, but I believe in the case "overkill" is a huge understatement.

Same goes with other tools: I have a few great beam torque wrenches. They don't measure angles, but a small angle adapter is cheap and does the job well. So, I don't foresee buying one of those $600 electronic torque wrenches that beeps when you hit the mark. What I'm using right now works well enough.

 

Yes

 

This thread was invaluable to my repairs. Thank you all for contributing.