Cylinder head rear plastic coolant pipe install problem.

[simon2]

Hi, this is my first post so hello to everyone. I am doing a cooling system rebuild on my Z3 1.9. I have bought all new BMW original hoses clamps plastic fittings, gaskets, etc, the works! Pulled the inlet manifold this weekend, so I have access to everything; no problem. Removed the plastic hose connector which is fitted to the block and it broke at the connection to the block as many seem to, not difficult to remove the remaining plastic in the block, cleaned up the hole nicely. Did the same with the plastic fitting on the back of the cylinder head, it broke off as well, not so easy to remove plastic bits still stuck in the head, but still doable.

However there was a lot of crud build up around the base of the fitting where it joined the cylinder head (must have been seeping coolant at some point very slowly). Unfortunately I found some corrosion right in the start of the hole, pitting almost where the O-ring will be seated from what I can see with an inspection mirror, horrible place to try and see what’s going on... and I thought working on my Triumph Stag was a pain in the ass... this car has just taken it to a new level!

I have cleaned the hole and removed all the corrosion, the pitting from what I can see may affect the O-rings ability to seal, something I will not really know until everything is put back and the car filled with coolant and tested. I was wondering if anyone has had this problem before?
I am thinking that perhaps some flange sealant maybe Loctite 518 just around the flange of the plastic fitting and enough to seep around the join near the O-ring but not on the O-ring itself to help with the sealing of the fitting against the head?
I know sealants are not supposed to be used with O-rings, but this is an exceptional case. I need a sealant that will not affect rubber and plastic of course.


Any other ideas guys? Don’t really want to have to pull the inlet manifold again if the pipe leaks at that dam join.

Thanks.

[Vintage42]

...Removed the plastic hose connector which is fitted to the block... found some corrosion right in the start of the hole, pitting almost where the O-ring will be seated... perhaps some flange sealant maybe Loctite 518 just around the flange of the plastic fitting and enough to seep around the join near the O-ring but not on the O-ring itself to help with the sealing of the fitting against the head?...

I see what you are dealing with (photos). I would not think a little sealant on the wide plastic flange would hurt anything, and might provide insurance.

But for the plastic flange on the metal head, the Loctite might not be best, as the literature repeatedly says it's for metal to metal. It might not even bond to plastic.
http://www.loctite.co.uk/loctite-408...=8802626633729

I think black RTV would be better. The literature says it's good for intake manifold end seals, and many intakes are plastic these days.
http://www.autozone.com/sealants-glues-adhesives-and-tape/rtv-adhesive/permatex-ultra-black-maximum-oil-resistance-rtv-silicone-gasket-maker/491386_0_0

[rf900rkw]

518 is not the stuff for this. Good old RTV. just the smallest bead right in the corner of the flange, outside of the o-ring.

- - - Updated - - -

And a PSA, why changing this piece is important:

m44-outlet.jpg


Pristine 97 M44 Z3, Only 80K miles. didn't matter. The 19 year old plastic nipple broke on the highway. Yes, it got so hot that it melted the plastic.

[Vintage42]

The OP's piece is the pipe on the block under the manifold. That piece is the other Y-connector piece on the back of the head. The head must have lost all coolant to get that hot. Probably the Y-connector failed as usual, with a crack at the head, causing loss of coolant, which then got the head hot enough to melt the plastic.

[rf900rkw]

Might wanna check the title of the thread and re-read the post. It's the heater neck on the back of the head giving the OP trouble.


Yes, the nibble broke off and dumped all of the coolant while cruising down the highway (I said that). It was run until it didn't run any more. The pistons now look a lot like that fitting. And, now that I have another engine in it, it is appearing some wiring inside the loom behind the head is also on the melted list..

[Vintage42]

Might wanna check the title of the thread and re-read the post. It's the heater neck on the back of the head giving the OP trouble.
Yes, the nibble broke off and dumped all of the coolant while cruising down the highway (I said that). It was run until it didn't run any more. The pistons now look a lot like that fitting...

OK, he broke both plastic parts, but was talking about sealing the Y-connector on the head as you noted.

Your first post with picture of a melted Y connector implied that was the cause of M44 1.9 coolant loss.

But my point is that the plastic parts don't melt and cause coolant loss. They break first.

As you say, the plastic Y on the head melted some time after coolant loss, around the same time that the heat seized the pistons down in the block. It takes extreme heat to melt the plastic, far above even overheated coolant temperature.

Edit: As to why the plastic Y-connector on the back of the 1.9 head eventually spontaneously breaks, I theorize that it is caught between the vibrating engine and the two heater hoses, and the stress works on it.

[rf900rkw]

I implied no such thing. I said quite plainly the nipple broke. That single failure has been the root cause of every single M44 failure I've worked on; cracked head (and worse) is the inevitible result.

[Vintage42]

... The 19 year old plastic nipple broke on the highway. Yes, it got so hot that it melted the plastic.

I implied no such thing. I said quite plainly the nipple broke...

Sorry, I just focused on the picture of the melted plastic. I thought you were saying if broke by melting.

[simon2]

518 is not the stuff for this. Good old RTV. just the smallest bead right in the corner of the flange, outside of the o-ring.

Thanks guys for all the answers, I'll do exactly that. Should I also try to fill some of the bigger pits with some epoxy metal weld? I can just get around there and see what I'm doing with a mirror!

[simon2]

Hey guys, here is a picture if any one was interested in seeing the problem. I managed to take a photo via a mirror which I used so I could see what I was doing and to try and clean up the corrosion. I have fitted the new coolant pipe and used RTV around the flange so hopefully that helps to seal because I don't think that O-ring is going to work very well. Still fitting all the rest of the hoses etc.

[Vintage42]

... used RTV around the flange so hopefully that helps to seal because I don't think that O-ring is going to work very well...

I don't think the O-ring has a good chance of sealing that messed up opening, either. And since the flange was not intended to need RTV, and uses only two bolts that seem more for retention than clamping, I wonder how long the RTV will be able to seal. Not a good situation.

1.9 Y-conn flange.jpg

[rf900rkw]

That is nasty. I have seen many with corrosion pitting that look like etching. That divot is a problem that will have to be filled. Never mind what I said about a light smear of RTV. You're going to have to fill that hole first. I have a product here called Quick Steel Aluminum Repair. Basicly an epoxy filled with aluminum dust. But working on this with the head in place will be... difficult. Part of me says try the epoxy, part says to load it up with RTV and hope., If it doesn't hold, you're pulling the head.

[RedRedZ]

Like Randy I was thinking of a filler. I would try to find or make a plug to insert with the filler so it leaves a smooth properly shaped surface. Maybe a little Loctite 620 when you mount the nipple. I have even heard of bondo being used on wet sleeve tractor diesels.

[simon2]

Part of me says try the epoxy, part says to load it up with RTV and hope., If it doesn't hold, you're pulling the head.

Yeah I thought everyone would freak when they saw that picture... I sure did when I enlarged it. Taking a photo via the mirror was the best way to see it!
I was stuck in the same quandary, mostly due to where its located and not being able to work on it accurately. I watched a you tube clip by Kent Bergsma:
https://www.youtube.com/watch?v=mxM-EXBx-8o (love watching his clips, always something to learn)
Sounds like you need to be able to get all that corrosion out from the pitting so that the Epoxy weld will adhere properly. So after watching that I was worried that I would not be able
to clean the area well enough and then sand it back to the correct shape, so I opted for your second idea and just put what I thought was enough RTV and bolted the fitting on!
So I guess I will try this and see what happens when all is under pressure.
When I took the water pump out there was no sign of any corrosion in the housing for this nor the plastic pipe hole in the block....

[rf900rkw]

While I agree those of good sealants (I use YamaBond ), they are not good for filling voids. Of course, if the outer perimeter seals well, the voilds no longer matter.

[simon2]

Just a follow up guys. cooling system overhaul is done. Intake manifold and all the wiring etc back in place. Tested the system no leaks. Flushed it twice and have been driving the car for a couple of weeks with new coolant and still no sign of a leak from the rear coolant pipe. Time will tell of course. That rear coolant pipe certainly is the Achilles heel of this engine....

[Colo Springs E]

If I were to take mine into a shop and have them replace the part Randy is referring to in post #3 (and I assume flush/replace the coolant), what is that part called? Is it just commonly called the plastic nipple at the back of the head?

[raubritter]

This might help you (it's a great resource for figuring out parts and part numbers):

http://www.realoem.com/bmw/enUS/part...6-Z3-BMW-Z3_19

I just used jan 1996 as build date, but you can use your specific VIN or build month to be more sure of correct parts.

Here is the one Randy is talking about (see part 9):

http://www.realoem.com/bmw/enUS/show...diagId=11_1561

And here is the one Vintage42 is talking about (part 1):

http://www.realoem.com/bmw/enUS/show...diagId=11_1558

The other pipes and hoses are found under 'cooling system.'

[Colo Springs E]

Here is the one Randy is talking about (see part 9):

http://www.realoem.com/bmw/enUS/show...diagId=11_1561

Thanks so much!!

[simon2]

Thought I would follow up after the replacement of that plastic hose connector on the back of the head of which I had issues with corrosion and possible sealing problems in 2017. It is still holding tight after what I did as explained in a post above. Might be useful for someone else with a similar issue.