Worm drive hose clamps and cold weather
 

I replaced my upper and lower radiator hoses and the three heater hoses in July with Mazda OEM hoses. I replaced the OEM-style prong clamps with stainless worm drive clamps from the auto parts store. I tightened them so they'd be good and snug but not cut into the rubber or deform the radiator inlet, etc.

It's been pretty cold here for the first time since I installed the hoses, and I smelled some coolant so I checked under the hood. The upper hose was seeping fluid at both ends and I checked the tightness of all the clamps. Every one of them was relatively loose so I tightened them all, about as much as I thought I did in summer. (As I was doing it, one clamp actually stripped some teeth out of the band so I'll need to replace it.)

Anyway, the question is do worm drive hose clamps loosen with severe temperature drops? Can they loosen over time? Did I just not tighten them enough initially? Are these clamps junk??

By the way, I replaced the hoses and clamps in my previous RX-7 which was also winter driven and never had a problem with leakage or clamps, so I'm a bit baffled...

Thanks.

Tightening them with just a screw driver is not effective, as I learned like you did. I have never had this issue with any other vehicle, but have had the same issue as you with my S5 vert. Best solution I have found is tightening them hand tight with a screw driver, then breaking out the 8mm wrench and putting 2 extra turns on them.

Also, some aftermarket radiators don't have the same hose neck angle as the stock rad. I have an after market radiator and the inlet and outlets on it are a few degrees different than stock. Obviously, this causes a stock fitting hose to not sit totally flush on the necks. The solution I came up with was to use two worm clamps on the radiator side and tightening them using the method above. No leaks to speak of, and no deforming of the inlet/outlet.

Just FYI, the radiator in question is a CSF radiator. It just doesn't fit right, so I wouldn't recommend anyone buy one for the RX7, unless you are on a budget. I used them before on other vehicles several times and they where great, but the RX& replacement radiators they make just don't fit right.

I've had the same problem with those junk worm drive clamps from Mexico, Thailand & China. I switched to stainless made in USA with no problems (I think I got them at ACE H/W. You probably did not get stainless-try sticking a magnet to it--if it's stainless, it WON'T stick to the magnet.

Check this site out:

http://www.idealclamps.com/catalog/index.php?ID=3

The clamps I used were given to me by Ray Crowe from Malloy Mazda. They were made in the U.S.A. but don't have a brand name. I see that a magnet does stick to it so I guess it's not stainless. Today I bought some "Ideal" brand clamps at Advance Auto that are the same size. They are also attracted by a magnet, so I guess they're not stainless either. Maybe I need to spring for some of the fancier clamps from MaczPayne's link, though I've never had this kind of issue before. Oh well...

Incidentally, I did tighten the clamps back in July using an 8mm socket. I guess I just didn't tighten them enough. Also I'm still using the stock Mazda radiator, jjwalker.

Thanks for the input everybody.

Worm drive clamps do that... look up Breeze constant torque clamps.

Not all Stainless steel is non-magnetic. It depends on how much nickel the particular type of stainless steel contains. http://www.physlink.com/Education/AskExperts/ae546.cfm

The 'magnet test' is not valid.

When I tighten hose clamps, worm gear or oem I use an electric driver with an adjustable clutch. Set the thing on a certain number and the torque is always the same-thight enough but not stripping it either. There are places I can't get to, heater hoses etc. but for the most part it works great.

And use a socket driver, not a screw driver bit.

Using an electric driver seems like a good idea, but how did you determine what setting would be the ideal torque for hose clamp screws?

Trial and error. If you get it too tight, it will cut into the hose or even strip. Too loose is pretty apparent as well. If it is too loose, you can twist the hose on the barb by hand. Tight enough and you cannot.

You can get "T" bolt clamps on Ebay for pretty cheap too. It's just a much better design than the screw type.