Threads Stripped In Radiator...Repairable?

[bmwman91]

So I was sitting at a light this afternoon and noticed that the temp needle was creeping towards the 3/4 mark. Once I started driving the temperature went back to the normal middle position. I assume that that means that it is just really low on coolant and not empty. There was also a coolant smell at the light.

When I got home and popped the hood, coolant was sprayed all over. The system seemed to be missing a good half gallon of coolant based on what I put in, and I have not run it since the bleed screw is the culprit, so more may be missing once I get the pump running. Adding coolant + squeezing the top hose repeatedly seemed to push a lot of air out of the system, so I did that until bubbles stopped being pushed into the expansion tank / the level stabilized. I can see bubbles come out around the bleed screw just from squeezing the top hose, so I am certain that the leak is serious enough that I shouldn't drive much until it is fixed. The threads in the radiator itself are what has been stripped.

My question is: Are the threads in the removable top bracket thing, or the radiator itself? Does this mean that I need a new radiator? If so, then I am going to seal the bleed screw in with some high temp RTV so that I can use the car until the new radiator comes, and I sort of need to drive it to somewhere besides my apartment since they get uppety about car repairs!

[roguetoaster]

Well, my thought is that as it is plastic the screw threads in to you could use a slightly larger bolt either just screwed in or tapped. If that does not work out I would use an epoxy instead of RTV. Of course the right solution is a new expansion/overflow tank.

How has the MM engine been treating you lately?

[monty23psk]

I hear there are copper bleeder screws that can re-thread the plastic going in. Not sure how well they will work in your case.

[bmwman91]

Well, I just went and pulled the little cover plate thing. Time for a new radiator. The stupid screw boss thing has a nice big crack in it that runs about 5mm off into the plastic body of the end cap. I smudged Ultra Grey RTV all over it, but I don't think that it'll help a whole hell of a lot. Hopefully the biggest part of the leak is dealt with (crack around the bleed screw itself).

I may just aim to do the radiator swap in the middle of the day when nobody is around lol. Would leaving the radiator cap loose help to keep pressure from building up in the system, or would that just be another place for coolant to piss out all over?

The MM engine has been treating me well so far. It pulls nicely all the way to 7700RPM!

[bmwman91]

Placed an order for a new Behr radiator from Pelican last night. Hopefully the car will make it the 5 miles to my house/driveway lol. If I time it right in the middle of the day there shouldn't be any traffic, and if I keep the RPM low it will hopefully get enough air flow and not build up too much pressure.

[monty23psk]

Remember to keep AC off as it will cause strain and extra heat on engine. Also if your heater core is still in the flow, heat all the way to help...I figure you know this but in the haste might forget. Good luck!

[bmwman91]

Haha AC...what is this AC that you speak of?!

But yeah, keeping the heat on should help. I think that I am going to drive the car about 200ft to a sort-of empty lot down the street and do the radiator swap in the street there. It isn't the property of my landlord, so poo poo to her!

I wish that I had more time and whatnot to plan. Then I could go with an all aluminum Mishimoto radiator and use a different / relocated expansion tank. Oh well, this one made it at least a decade, so presumably the new one will too.

[bmwman91]

I got the new radiator swapped in at lunch today. Talk about bullshit though...the bleed screw on the new one stripped. I can't tell if it is the screw or the threads in the radiator. It is not like I overtightened the thing...I've done this a zillion times. WTF? It does not leak, but I assume that it is only a matter of time before it does. My assumption is that the bleed screw is what should strip since it is made from a softer plastic. Maybe this is why people use the brass bleed screws?

[roguetoaster]

Rough. I assume people use the brass ones as the slots for the screwdriver do not strip out as easily. You should contact the seller of the radiator and request a new one be shipped after explaining that the car is your DD and thus cannot be down for shipping (I am sure they will want you to buy a new one and will refund after getting the newly stripped one).

Maybe it will make you feel better to know that having bled brakes many, many times, and not one bleed screw broken, I broke 2/4 bleeder screws last time I did it. It's just one of those things, fine for years and years, and then you ruin several in one week, never to happen again (to that part at least).

[bmwman91]

Yeah, I emailed Pelican to ask for a replacement bleed screw. If that doesn't work then I will see if I can get them to send a fresh radiator.

[bmwman91]

Did a little dumpster diving and pulled the bleed screw from my old radiator. Luckily, it was in better shape than the "new" one and it threaded in fine. Good thing they make the screw from a softer material then the radiator! (probably intentional for obvious reasons)

Here was the new one. Didn't take much to make it worthless.


Old one. Must have been a harder material, or I was just being way more careful with installing it. Still beat up enough that I am asking Pelican to send me a free new one lol. FUCK I hate plastic threads.


Basically, the reason these screws are such a pain in the ass for everyone is because they are used sort of the same way that the valve cover bolts are (and everyone strips them lol). It is set up to limit the compression on the rubber O-ring so that it doesn't get over-compressed and split/crack. So, tighten it JUST enough that the plastic screw head hits the plastic radiator boss. Stop there as that is the best seal you are going to get. Here's a little illustration.

[Gerta]

This is a diagram that any lunk head like myself could follow. Thanks Bmwman

[bmwman91]

Glad it helps. Everyone knows that they aren't supposed to over-tighten things. It always helps a lot when you can clearly see WHY, particularly with this stupid bleed screw!