Cooling system - One weak point.

Here is a photo of one of the main culprits for coolant leaks.


Yes it's the radiator bleed.

The problem s usually stem from this being overtightened after bleeding air from the radiator.
What you have is a threaded plastic bolt tightening into the plastic radiator casing. Easily overtightened and then it will leak.


The area that the bolt screws into is only 5mm thick meaning that the actual number of threads holding this crucial bolt in is only about 3-4 threads. Overtorque even slightly and OOPS!

I've been thinking of ways to eliminate this weak point in the cooling system and came up with two ideas.
1/. Use a metal 'Rivnut' and bolt to replace the plastic.
This is what I'm talking about.


Now there are two different ally rads available with different thread sized apertures.
Mine has an M12 thread and an M8 Rivnut is a pretty good fit for this size.


As I didn't intend this to be my final solution, I wrapped the rivnut in PTFE tape before inserting it and tightening it with the applicator. Otherwise I would have coated the outside surface of the rivnut with an appropriate epoxy adhesive




Then an 8mm Stainless Steel bolt with an appropriately sized 'O' ring fits the rivnut.

I ran the car with this setup for 7 days with no leaks.
However, it still leaves the problem of overtightening and dislodging the rivnut.

I ideally wanted a permanent fixing that would not need to be removed if bleeding the radiator.

I recently fitted an auto bleed valve into my domestic heating system, and that got me thinking.
I found a small auto bleed valve that works at up to 120 degrees C ans 10 bar.
Here
The micro version seemed to fit the bill.
I permanently screwed the lower part into the radiator using epoxy resin, and allowed it to set.


After a sufficient time, I screwed the auto vent capsule in place by hand.

Hi David,
Being as you have not made it permanent by not using epoxy resin, what is your second idea and how will you remove the rivnut.I actually like the first idea,can you get stainless rivnuts and is there any chance of damaging the rad with excessive tightening of the rivnut?
Regards Neil

Hi David ,
You must be psycic,you answered my question one minute before I asked it.
Regards Neil

neilowen1 wrote: Hi David,
Being as you have not made it permanent by not using epoxy resin, what is your second idea and how will you remove the rivnut.I actually like the first idea,can you get stainless rivnuts and is there any chance of damaging the rad with excessive tightening of the rivnut?
Regards Neil

Guess we cross posted.:lol:

I actually was testing what sort of torque I could put on the bolt and the rivnut came loose, hence version 2.
I reckon epoxying in the rivnut would be a pretty good alternative to my 'Final Solution'

neilowen1 wrote: Hi David ,
You must be psychic,you answered my question one minute before I asked it.
Regards Neil

Neil,
It must be true, my Psychiatrist says I'm psychic...no wait... psychotic, that's what he said!:rofl:

You can get stainless rivnuts, I used alloy ones. As to damage, the thread on mine was pretty mangled anyway, but the rivnut hadn't made it any worse, tbh.

Hi David,
Was there a compatible thread on the auto bleed valve or was it an interferance fit?
Regards Neil

hi david wouldnt be better just to get the mike satur bleed nipple, just a thought

rayb wrote: hi david wouldnt be better just to get the mike satur bleed nipple, just a thought

Ray, I tried it and wasn't impressed to be honest. alloy fitting, steel bleed nipple = seized.
= Try to loosen the bleed nipple, and the whole thing unscrews.
Well that's what happened to me, plus the fitting only fits the OEM thread.:shrug:

Just to update, there was some air left in the radiator after I had fitted this auto bleed valve. The next day the air had auto-purged and after topping up the expansion tank it hasn't moved since.
This vent has been in place for 10 days now.

This shows the auto vent works, allowing air out but not coolant.

david aiketgate wrote: Just to update, there was some air left in the radiator after I had fitted this auto bleed valve. The next day the air had auto-purged and after topping up the expansion tank it hasn't moved since.
This vent has been in place for 10 days now.

This shows the auto vent works, allowing air out but not coolant.

They are a very clever peice of kit, the internal seal will let air past and seal tight as soon as liquid comes. they will not suck air back in either as the system cools down and the pressure reduces (as in Combi boiler systems) I fitted two of theses Auto vents on Ma-in- law's heating system on to two radiators that were collecting air daily and completely solved the problem, because they auto vent. ~ i have an new OEM rad on my F and have a Mike Satur blled nipple to fit, might change my mind and fit the" AIKETGATE Patented Auto Vent" :shrug: a great idea