removal of hose clamps

[jtwerp]

The hose clamps that are "pinched" to tighten them, whats the easiest way to remove them without destroying what they are holding, would you recommend using new ones of that type or just use the worm gear clamps? Basically is one better than the other, or is it just preference?

[JDS60R]

To remove the pinch or oetiker clamps you can cut the pinch area staying away from the hose.

Worm drive clamps are the lowest performing of the clamps on the market. They are referred to as a constant dimension clamp meaning they have no ability to change size (without your help) as the fitting and hose expand/contract due to temp. Worm clamps are worse than pinch or oetiker as the hose gets pushed through the cuts for the worm drive each time the fitting goes through a heat cycle. They are basically self loosening by means of destroying the hose. That being said- they can and have worked ok as long as they are not put on too tight and are tensioned occasionally.

The oetiker is a banded clamp so it is also a constant dimension but has a band to protect the hose from the damage stated above. They are better than worm clamps.

Next up is a constant tension clamp. These are the spring steel or spring assisted variety and do a better job than the constant dimension.

Finally there are polymeric clamps that self adjust and keep leaks from occurring. These are the type I install as they do the best job. here is a short marketing video to help explain the issues at hand. These are the clamps I use on my cars. They are expensive $3-$5 per clamp (O'Rielys) but more than worth it in my opinion.

[urbex]

So these SB clamps..looks like they are some kind of heat shrink plastic, similar in concept to the heat shrink tubing used for electrical wiring, so that they're a one use only kind of deal? Looks like they would be non removeable without injuring the hose in some way. Not so sure I'm all that wild about that part, but I do see where they would be much more effective than the other types as far as sealing goes.

As far as removing the Oetiker clamps, I'll usually just wedge a screwdriver in the part that would get squeezed down, and work it apart, or use needlenose pliers to work it loose. I've never had a case of injuring the hose underneath doing it this way. If I'm going to be replacing the hose anyways, I'll avoid the hassle, and just cut it off with a dremel+cut-off wheel.

[Ozark Lee]

I guess I fall into the "Old Dog" camp, I had never heard of such a clamp. Do they make them small enough to go around the Effing elbow on the PCV line at the end of the intake manifold?

The video showed applications where the heat gun could be applied uniformly around the connection - what about applications where you don't have room to get the heat gun all the way around the connection? The engineer in me is thinking that the heat from the engine will continue the seal process even if the heat gun can't.

Even as an "Old Dog" I like new tricks and I have heat guns.

...Lee

[urbex]

I guess I fall into the "Old Dog" camp, I had never heard of such a clamp. Do they make them small enough to go around the Effing elbow on the PCV line at the end of the intake manifold?

According to http://www.gates.com/brochure.cfm?broch ... ion_id=546 they have clamps to go from 1/4" to 3-1/8" ID hoses.

[JDS60R]

Lots of questions - here are some answers.

They can fit as small as 1/4 inch and as large as 3.5 inch. You can get bigger but they are sold at truck repair shops

They are easily removed with a pushing blade or a soldering iron and cause no damage to the hose.

They are a one time application. If you have to keep taking off the hoses then other issues are at hand. Once these are on I just leave them on until its time to change the hose, or radiator. its usually years at a time. Having no leaks and no maintenance/tightening on the clamps makes them a very nice addition.

These are awesome on the flame trap/PCV style connections. Having the oil leaks/seepage stop is wonderful for keeping the motor clean. You can use them on everything except fuel line. The trans coolers I install have these on them and never leak. The installation looks perfect as well.

They need 1/3 of the outside to receive heat. It reaches is maximum tension at 300 degrees F. Once the car is warmed up they self tighten even more. I have had some that I could barely get the hot air to and they did not leak at all as the warm coolant tightens them well before the pressure had a chance to effect them.

When using them in tight places with a plastic fitting like the coolant reservoir use high heat to shrink them tightly. The plastic fitting does not get hot as quickly because it is small. The high heat gets it on tight quickly as you do not want to melt the plastic reservoir with a lengthy heating.

[Grunchy]

Regarding "worm gear" hose clamps, the only actual problem with them is some mechanics go nuts over-tightening them.
Here's the fact regarding thermal expansion of metals, specifically steel: steel "grows" by 5.9 millionths of an inch, per inch, per degree Fahrenheit heating.
Actually let's go with an aluminum nipple, which has thermal expansion 13.0 millionths of an inch, per inch, per degree Fahrenheit.
That means, let's suppose you install the hose clamp at 72 degrees F, and it is tightened properly. And let's suppose the hose nipple is 2" diameter.
And now let the cooling system warm up to 170 degrees F, that's about 100 degrees F hotter than when the clamp was installed.
The aluminum nipple will expand by 13.0 millionths of an inch, per inch, per degree F. Multiply 0.000013 inch/inch x 2" x 100 deg F and you get 0.0026" expansion - of the aluminum nipple!
But wait, the steel worm clamp grows too (let's suppose it gets just as hot as the rest of the cooling system).
Multiply 0.0000059 inch/inch x 2" x 100 deg F and you get 0.00118" expansion.

So the reality is, the aluminum hose nipple expands by 2.6 thousandths of an inch whereas the clamp expands by 1.2 thousandths of an inch.
What happens to the extra 1.4 thousandths of an inch? Well, the hose gets squeezed that much due to differential thermal expansion.
Oh wait, let's suppose I press on the surface of a hose with my finger with 5 lbs of force, doesn't it bend more than 1.2 thousandths of an inch under that extreme pressure?

So, guys, gimme a break about hose clamps and thermal expansion causing excessive distortion. It's a bunch of hogwash from people who should know better.

[scot850]

Well, as a fellow mechanical engineer, I agree with your math on the expansion and contractions of the various materials. The issue I have with worm type clamps is that they don't pull round or evenly. That is probably why many mechanics over tighten them. Then there is the quality of the current crap we are sold in most auto shops. The Volvo clamps for the older cars had a rounded profile on the edges which do not cut into the rubber hoses when tightened. Then where there are higher pressures on larger clamps like the intercooler hoses they have an additional sleeve so the clamp does not bite into the hose under the worm area which does not conform to the pipe diameter. Those hose clamps do pull round as they are designed to work in the size range of the hoses they are used on.

The biggest issue is using too large a clamp on a smaller hose. Those will often leak.

In the end, use what you like, just make sure it is safe for the application.

A good example of the poor use of worm clamps is the hose on the 5 cylinder engines from the PCV tank to the top of the cylinder head. I have had to clean many cars where this type of clamp has been used and and the rubber hardens and the pipe comes off or leaks oil all over the top of the cylinder head. Fuel lines is another area I do not recommend using them on small hose diameters.

Have a good day everyone!

Neil.