Coolant leak, common location/failure mode?
- Thread starter Mr Whippy
- Start date
My thermostat failed- warranty covered it otherwise 90 all in to fully replace.
£90 for a replacement, and fitted? Was that BMW with an OEM part? I'm certain the part alone was £100?!
I had a check again earlier and I think my sensor seal o-ring is the culprit.
I started the engine and it looked like it was leaking from the rubber > plastic end piece union join... BUT, the sensor can leak and the leak runs onto that joint and then down the pipe...
I turned the engine off and pressed the sensor up/down in the engine bay and when pushing it one way it would stream out, down the sensor housing, across the pipe union and down the pipe and drip over the aux belt. Pull the other way and it'd stop dripping right away!
It looks like a pretty bad leak by all accounts... I'm surprised the sensor o-ring can fail so badly.
So hopefully the o-rings will arrive tomorrow and I can do a quick swap and test... re-top up and bleed or whatever else...
Then it'll be aux belt DIY. Then it's due an oil service which it can go to BMW for, and probably get the rear diff oil seals done and new oil while it's there... and gearbox oil too I think.
That'll be a nice £400 invoice hehe
Dave
I had a check again earlier and I think my sensor seal o-ring is the culprit.
I started the engine and it looked like it was leaking from the rubber > plastic end piece union join... BUT, the sensor can leak and the leak runs onto that joint and then down the pipe...
I turned the engine off and pressed the sensor up/down in the engine bay and when pushing it one way it would stream out, down the sensor housing, across the pipe union and down the pipe and drip over the aux belt. Pull the other way and it'd stop dripping right away!
It looks like a pretty bad leak by all accounts... I'm surprised the sensor o-ring can fail so badly.
So hopefully the o-rings will arrive tomorrow and I can do a quick swap and test... re-top up and bleed or whatever else...
Then it'll be aux belt DIY. Then it's due an oil service which it can go to BMW for, and probably get the rear diff oil seals done and new oil while it's there... and gearbox oil too I think.
That'll be a nice £400 invoice hehe
Dave
Mr Whippy said:It looks like a pretty bad leak by all accounts... I'm surprised the sensor o-ring can fail so badly.
So hopefully the o-rings will arrive tomorrow and I can do a quick swap and test... re-top up and bleed or whatever else...
Dave
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Hope the O-ring does the trick.....mine is fine now.
Just got the O-rings... their 1st class delivery seemed a bit slow. Ah well here now.
So, any tips on an easy removal of the sensor and re-fit without taking other stuff off around the car?
I can press the top clip in ok but that one on the underside is gonna be a nightmare hehe... might remove the sensor harness clip first to make a bit of room!
Hmmm
Dave
So, any tips on an easy removal of the sensor and re-fit without taking other stuff off around the car?
I can press the top clip in ok but that one on the underside is gonna be a nightmare hehe... might remove the sensor harness clip first to make a bit of room!
Hmmm
Dave
The o-ring seems to have done the job. I've put in as much coolant as it looked like came out when I swapped the part and the level seems about right. A quick 2 min idle showed no coolant running out the sensor now, all bone dry around there. Yay.
Now to bleed it.
Does anyone have a good FAQ/guide for bleeding this engine?
Looks like it's heater on max, top up to max level, run engine, and just leave bleed screws open till they blow water, then close up. Let it cool, re-top up coolant expansion tank. Is it just the bleed screw on the top of the expansion tank I need to worry about on this job (post thermostat drain basically)?
I also think I'm best parking the car aiming slightly up-hill rather than slightly down-hill, so the air rises easily to that front bleed screw?
Thanks for any help/advice!
Dave
Now to bleed it.
Does anyone have a good FAQ/guide for bleeding this engine?
Looks like it's heater on max, top up to max level, run engine, and just leave bleed screws open till they blow water, then close up. Let it cool, re-top up coolant expansion tank. Is it just the bleed screw on the top of the expansion tank I need to worry about on this job (post thermostat drain basically)?
I also think I'm best parking the car aiming slightly up-hill rather than slightly down-hill, so the air rises easily to that front bleed screw?
Thanks for any help/advice!
Dave
CarmadJames
Member
Hi Dave
Glad to hear it's finally sorted. Sounds like you have the bleeding sorted too. Front end as high as you can get it. I had mine up on ramps up a hill.
For a couple of days after I did mine I checked it first thing in the morning, when the engine was cold, by opening the bleed screw. For the first day or 2 a tiny bit more air would come out. That seemed to be it. I had heard these cars were hard to bleed but it was actually straightforward and has been good since.
James
Glad to hear it's finally sorted. Sounds like you have the bleeding sorted too. Front end as high as you can get it. I had mine up on ramps up a hill.
For a couple of days after I did mine I checked it first thing in the morning, when the engine was cold, by opening the bleed screw. For the first day or 2 a tiny bit more air would come out. That seemed to be it. I had heard these cars were hard to bleed but it was actually straightforward and has been good since.
James
The bleed screw is a pain though, it's really hard to turn and isn't a standard tool shape, so my cross-head screwdriver (biggest I had) rounded the head off, so I was back to the flat head screwdriver... but it almost needs a special tool.
Then it feels stiff due to the hot water when bleeding hehe.
I need to do another bleed on mine to make sure the last of the air is out but for now it seems to be running perfectly fine... I suppose it can auto-bleed a bit since there is a take-off pipe from the bleed area that runs directly into the top of the expansion tank...
All good though
Dave
Then it feels stiff due to the hot water when bleeding hehe.
I need to do another bleed on mine to make sure the last of the air is out but for now it seems to be running perfectly fine... I suppose it can auto-bleed a bit since there is a take-off pipe from the bleed area that runs directly into the top of the expansion tank...
All good though
Dave
Hey guys!
So new to this forum and new to the BMW Z4. When I got out of my car I noticed there was quite a huge puddle of coolant dripping from my car. I took a video and I'm trying to figure out where exactly it is coming from. I enclosed some pictures and narrowed it down to this blue screw and what ever is on top of it.
From these pictures can anyone tell me what part this leak is coming from so I can get it replaced if it needs to be replaced?
So new to this forum and new to the BMW Z4. When I got out of my car I noticed there was quite a huge puddle of coolant dripping from my car. I took a video and I'm trying to figure out where exactly it is coming from. I enclosed some pictures and narrowed it down to this blue screw and what ever is on top of it.
From these pictures can anyone tell me what part this leak is coming from so I can get it replaced if it needs to be replaced?
Attachments
Nice thread resurrection. I haven’t had this problem, but I’m pretty sure the blue plug is the coolant drain plug. The coolant expansion tank sits above this and is one of the more common failure points reported on this forum. It can crack and will need replacing, but check all your hoses/connections first.
Looks like the bottom of the expansion tank? Front left corner?
The tanks have a habit of getting a hairline crack and leaking as they get hot.
I had a similar leak, which actually turned out to be the O-ring seal where the tank push fits into it's housing, but given the age of the car and the known split tank issue I changed the whole thing. Not too difficult a job, and lots of how-to's on here and youtube.
Is you're an auto? If so, there's a bypass valve inside the bottom housing that can break when you remove the tank, due to the plastic getting brittle over the years. Happened to me: took the tank off and the spring in the valve fired the top half of it out of the car! So if you have an auto, get a new valve at the same time.
The tanks have a habit of getting a hairline crack and leaking as they get hot.
I had a similar leak, which actually turned out to be the O-ring seal where the tank push fits into it's housing, but given the age of the car and the known split tank issue I changed the whole thing. Not too difficult a job, and lots of how-to's on here and youtube.
Is you're an auto? If so, there's a bypass valve inside the bottom housing that can break when you remove the tank, due to the plastic getting brittle over the years. Happened to me: took the tank off and the spring in the valve fired the top half of it out of the car! So if you have an auto, get a new valve at the same time.
Hi I have a leak from the bottom of my expansion tank in my 2.5. If I move the pipes going up into the base it leaks a bit and move them again it stops. The tank looks ok - no sign of a split. I cleaned the o-rings and reinserted the bottom pipes but it doesn't seem like a secure fit. Any thoughts?
If you could find the correct sizes.DoaghZ said:
Tbh, for about £40 and an hour or so of your time you'd be better swapping the tank. If the seals are leaking then putting new ones in could lead to the little bit of extra pressure needed to split your old tank.
