My Luck with Coolant Hose Clamps!

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With the help of a friend, I recently replaced the heater hose, flange and flange gasket (paper) on the back of my BMW's M50 engine. Given this necessitated removal of the manifold, it wasn't exactly a "fun" repair. Here is a photo of the 24 year old, leaking heater hose: http://gdurl.com/mQPC

Anyway, we got it all back together again, bled the cooling system and things were fine for the first few drives. After several drives, I noticed there was a slight weep from the hose or the flange itself again. By a couple of drives later, it was leaking enough to drip on the ground...

Now, if this were a sealing issue on the water flange itself, that would've manifested straight away, I think. I've had plenty of issues with worm-drive hose clamps expanding after a few drives and beginning to seep - I'm just wondering if anyone else has had the issue?
I don't tighten things down as hard as I can (I could've, given this is a metal flange), but the hose was by no means loose.

Any suggestions? I've got another six hoses to replace shortly, all of which are far more accessible. However, I'd like to avoid this irritating phenomenon if I can!

Makes me wonder how mechanics can remove and reseat coolant hoses everyday without having things start seeping everywhere.
 
Was the sealing surface for the flange on the head pitted and corroded? I've seen that before
 
Originally Posted By: Seventh
Was the sealing surface for the flange on the head pitted and corroded? I've seen that before

Nope, used a brand new flange as I anticipated the old one would be old and crusty.
 
I always coat the flange with a little Hylomar M before putting the hose on. It doesn't harden so removing the hose later is no problem and is superior to silicone or #2, it will never leak again.
Use a constant tension clamp in place of worm clamps, the OE BMW worm clamps are much better than the five and dime junk available in parts stores these days but are not as good as constant tension ones, the only downside with them is price.
 
Originally Posted By: Trav
Originally Posted By: knerml
German OEM's use spring tension clamps. They automatically adjust to changes in the hose over time.

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2555940


Really?

https://www.ecstuning.com/b-genuine-bmw-parts/hose-clamp-worm-gear-stainless-steel/07129952113/

German OE can be crimp, worm or spring, they use many types.



Usually any hose that carries coolant, which causes a large temperature variance, will not have a gear clamp. A gear clamp will not maintain constant tension during heat/cool cycles. So you will only find gear clamps on things like fuel hoses and such.

Never use gear clamps on anything that gets hot.
 
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Originally Posted By: Trav
I always coat the flange with a little Hylomar M before putting the hose on. It doesn't harden so removing the hose later is no problem and is superior to silicone or #2, it will never leak again.
Use a constant tension clamp in place of worm clamps, the OE BMW worm clamps are much better than the five and dime junk available in parts stores these days but are not as good as constant tension ones, the only downside with them is price.


Trav, why the Hylomar M vs. the universal blue? Their website implies that the blue is the more "go to" product. I have never used either. Thanks.
 
Originally Posted By: Egg_Head
+1 BMW OEM clamps, then light a candle and say a prayer

I haven't had a problem at all with the BMW OEM clamps (typically NORMA brand). Despite my personal attraction to the spring clamps on my Asian cars, I have to say the BMW ones haven't leaked either.
 
Originally Posted By: mightymousetech
Originally Posted By: Trav
Originally Posted By: knerml
German OEM's use spring tension clamps. They automatically adjust to changes in the hose over time.

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2555940


Really?

https://www.ecstuning.com/b-genuine-bmw-parts/hose-clamp-worm-gear-stainless-steel/07129952113/

German OE can be crimp, worm or spring, they use many types.



So you will only find gear clamps on things like fuel hoses and such.

Never use gear clamps on anything that gets hot.


Lots of companies use worm clamps OE on cooling systems, they are cheap, look at more than domestics. Notice BMW uses a protective sleeve on this larger hose. Honda uses worm clamps almost exclusively on every coolant hose on some of their bikes. I agree they are not the best option by far.



Originally Posted By: doitmyself
Trav, why the Hylomar M vs. the universal blue? Their website implies that the blue is the more "go to" product. I have never used either. Thanks

All the Hylomar blue products are very similar but the M is slightly thicker and less runny, you can find it on ebay cheaper than Amazon. Once you use it you will never be without it.
 
B320i Nope said:
I was asking about the surface on the head.

And BMW has always used only worm gear clamps or oetiker clamps up until E46 was introduced.

Edit: I'm a big fan of hylomar products as well, also there is an equivalent version made by wurth, called DP 300
 
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You need constant tension hose clamps and Mayhew 28680 pliers to go with them. Problem solved.

DMR_CTB-HoseClamp_300x300.jpg


wk3d77.jpg


28680_Mayhew.5710fdf678671.jpg
 
Originally Posted By: Seventh
Originally Posted By: B320i

Nope, used a brand new flange as I anticipated the old one would be old and crusty.


I was asking about the surface on the head.

And BMW has always used only worm gear clamps or oetiker clamps up until E46 was introduced.

Edit: I'm a big fan of hylomar products as well, also there is an equivalent version made by wurth, called DP 300

My apologies, I misinterpreted what you said.

As far as I could tell (given this [censored] sits at the back of the engine and is hard to see), the surface was smooth.

Tried tightening the hose clamp - yep, it had loosened up a bit from heat cycling, but that didn't solve the issue. Seems the leak is during warm-up, and once warmed up, the coolant stops flowing. No smell of evaporating coolant either.

Should've just taken the approach as with the metal thermostat housing I used - use a bit of RTV in lieu of some paper gasket that is liable to move around while tightening and not seal particularly well.
 
Have tried reseating the clamp a couple of times now, and it still seeps some (particularly during the warmup phase). Could just be a [censored] clamp, or maybe the actual flange isn't perfectly sealed.
 
In my experience all you need is Permatex #2 and tighten the screw clamp tight. I don't pussyfoot around and tighten it to the point where you think you'll start digging in if you tighten any more.
 
Were OE parts used? Are you sure the hose and flange are properly aligned and fitted together?

The tightest clamp in the world isn't go to prevent a leak if the mating surfaces aren't doing their job.

It's not the clamp's job to create the seal. The clamp's job is to keep the parts together and the seal intact.
 
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