E46 coolant weep - heaterbox?
E46 coolant weep - heaterbox?
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dhutch

Original Poster:

17,907 posts

228 months

Thursday 8th November 2018
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Got a persistent slow leak. Doesn't show up on a pressure test, doesn't show up on UV.

Car has had new rad, waterpump, thermostat, pipework recently. Garage (z4 specialist) is suggesting heaterbox but says it's very labourious on the Z4 and might be the same on the 330ci but needs to look into it.

Thoughts welcome.


Daniel

Sardonicus

19,461 posts

252 months

Thursday 8th November 2018
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If its from the heater matrix it will show up on a UV test traces on carpets etc, plus you can usually smell it in the cabin the other give away will be on start up on a cold morning put heater to hot and fan on you will see the screen instantly mist and steam up instantly and may even taste the coolant in the interior atmosphere , heater matrix problems are usually obvious and to be losing coolant to noticeable levels even Stevie Wonder could diagnose

louiebaby

11,000 posts

222 months

Thursday 8th November 2018
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Had similar problems in my E39, (similar vintage in terms of BMW weakness, I suspect.)

I chucked some of the better rad-weld stuff from Halfords in, and it's been fine since.

It it was concourse, of course the whole lot would come out and be fixed properly, but it's not. Sadly. The wife and kids have seen to that.

kev b

2,756 posts

197 months

Thursday 8th November 2018
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Have the garage tested the head gasket?

dhutch

Original Poster:

17,907 posts

228 months

Thursday 8th November 2018
quotequote all
Yeah, I've had bad coolant leaks in the cabin so aware of the symptoms if it's bad and am getting none of that, which I have told them. However it is a reasonably small leak, like a pint in 500miles type leak.

Current thinking is it might be the filler cap, the one bit you don't test with a leak test obviously. Apparently although reasonably new it damaged.


Daniel

dmarkovina

639 posts

114 months

Saturday 10th November 2018
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Checked the the temp sensor o ring - next to the radiator?

dmarkovina

639 posts

114 months

Saturday 10th November 2018
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Also top radiator hose is a common weak spot - crack only visible from the inside - engine side. And it weeps invisibility.

dhutch

Original Poster:

17,907 posts

228 months

Saturday 10th November 2018
quotequote all
Pressure tested, UV die, nothing. Held overnight.

Has had new rad after the GSF spec one lasted 18month, and with that a new res and tophose, and rad cap was pretty new too. However it appears that has failed. So next plan is swap that out, sort the oil weep, and drive it for a bit!

Rad cap like most of the rest is genuine BMW and done about a year, which is fairly crap in my book. Unless it's been compromised by the GSF spec rad that was fitted in a rush as it was available.

Daniel