Coolant leak - Rear of engine

[Robin82]

Unfortunately I have a coolant leak at the rear of the engine. The leak is dripping onto the exhaust manifold. It is dripping directly off of the engine next to a plastic plate bolted to the back of the engine.

The car is not overheating and runs ok. Although the heater is now only blowing out cold air.. It also seems to lose coolant at a slightly faster rate when I first top it up and then levels out.

Any idea’s what this might be?

I am obviously praying it is not the head gasket. Usually it would overheat if it was?!

I have read about ‘freeze plugs’ or ‘core plugs’ although I cannot find much about them to the point I’m not sure they exist! Incidentally, the issue first arose after we have had this bitterly cold weather.

Any idea’s?!

 

[bigwinn]

I’d say the first place to check is where the coolant flows via hoses from the block to the heater core

There are usually an in and an out hose on the bulkhead

 

[Robin82]

I’d say the first place to check is where the coolant flows via hoses from the block to the heater core

There are usually an in and an out hose on the bulkhead

Both pipes that feed the heater core are stone cold. I can see no leaks coming from these pipes out of the bulk head. I will double check again tomorrow once the car has been running again…

 

[bigwinn]

enuff_zed

do you have any other suggestions being more knowledgable of the 2.0 block?

 

[enuff_zed]

I had a similar issue, which in my case turned out to be a failure of the auxiliary water pump, mounted on the left inner wing below and to the rear of the airbox. This allowed an airlock to form in the heater matrix.
Both pipes from the heater matrix run to the front of the engine bay. One from the auxiliary pump and the other back to the expansion tank.
Therefore thee only way they could produce water leaks at the rear of the block is if the water is spraying from them onto the back of the engine.
I'm at work today so cannot look at my engine to see what this plastic plate is?
If water is definitely coming from that then it needs investigating further (master of the bleedin' obvious! :roll: )
I suspect the coolant level dropping is what has created an airlock in the heater matrix and preventing coolant flowing through that.

 

[Robin82]

I had a similar issue, which in my case turned out to be a failure of the auxiliary water pump, mounted on the left inner wing below and to the rear of the airbox. This allowed an airlock to form in the heater matrix.
Both pipes from the heater matrix run to the front of the engine bay. One from the auxiliary pump and the other back to the expansion tank.
Therefore thee only way they could produce water leaks at the rear of the block is if the water is spraying from them onto the back of the engine.
I'm at work today so cannot look at my engine to see what this plastic plate is?
If water is definitely coming from that then it needs investigating further (master of the bleedin' obvious! :roll: )
I suspect the coolant level dropping is what has created an airlock in the heater matrix and preventing coolant flowing through that.

Hi enuff_zed, thanks for your input. So it seems that the part that I mentioned previously being attached to the back of the engine block is called a ‘cover plate’. It’s sort of shaped like a vent, one larger and one smaller circle and is sealed on with O rings. See this link (part number 17)

https://www.realoem.com/bmw/enUS/part?id=BZ12-EUR-02-2007-E85-BMW-Z4_20i&mg=11&sg=15&diagId=11_3178&q=11537583666

I will have another check around the area this evening. Blown Head gaskets are usually an internal leak aren’t they?

 

[enuff_zed]

I had a similar issue, which in my case turned out to be a failure of the auxiliary water pump, mounted on the left inner wing below and to the rear of the airbox. This allowed an airlock to form in the heater matrix.
Both pipes from the heater matrix run to the front of the engine bay. One from the auxiliary pump and the other back to the expansion tank.
Therefore thee only way they could produce water leaks at the rear of the block is if the water is spraying from them onto the back of the engine.
I'm at work today so cannot look at my engine to see what this plastic plate is?
If water is definitely coming from that then it needs investigating further (master of the bleedin' obvious! :roll: )
I suspect the coolant level dropping is what has created an airlock in the heater matrix and preventing coolant flowing through that.

Hi enuff_zed, thanks for your input. So it seems that the part that I mentioned previously being attached to the back of the engine block is called a ‘cover plate’. It’s sort of shaped like a vent, one larger and one smaller circle and is sealed on with O rings. See this link (part number 17)

https://www.realoem.com/bmw/enUS/part?id=BZ12-EUR-02-2007-E85-BMW-Z4_20i&mg=11&sg=15&diagId=11_3178&q=11537583666

I will have another check around the area this evening. Blown Head gaskets are usually an internal leak aren’t they?

Would be most unusual to have a head gasket pour water out of the head. Plus it would do it under greater pressure and probably come out as steam. I did see that cover plate on realoem this morning actually. Apart from losing more coolant it looks simple enough to fit new seals.
They are a pig to fill and bleed though. Put the front end up on ramps to make the expansion tank the highest point and fill slowly. Then start the engine and continue to fill. Even then it's 50:50. Maybe worth asking a garage to bleed it using their fancy vacuum systems?

 

[Robin82]

So after further investigations around the rear block I’m
90% sure the leak is coming from this ‘cover plate’ and the. Dripping a few inches further along and off the corner of the engine and onto the exhaust.

I’m not sure of the purpose of this cover plate. It doesn’t seem to serve one :roll:

I should be able to get a small socket wrench in behind the block and the heat shield. Will be a little fiddly but should be ok.

I’m also assuming I have the mother of all air locks in the system too…

 

[enuff_zed]

So after further investigations around the rear block I’m
90% sure the leak is coming from this ‘cover plate’ and the. Dripping a few inches further along and off the corner of the engine and onto the exhaust.

I’m not sure of the purpose of this cover plate. It doesn’t seem to serve one :roll:

I should be able to get a small socket wrench in behind the block and the heat shield. Will be a little fiddly but should be ok.

I’m also assuming I have the mother of all air locks in the system too…

While you're in there, pop the two pipes off the heater matrix and blast through with a hose pipe, swapping directions every now and then. It won't shift an airlock, but if nothing has been going through there for a while the sludge will have started to settle. Get it out while you can.

 

[Robin82]

I had a similar issue, which in my case turned out to be a failure of the auxiliary water pump, mounted on the left inner wing below and to the rear of the airbox. This allowed an airlock to form in the heater matrix.
Both pipes from the heater matrix run to the front of the engine bay. One from the auxiliary pump and the other back to the expansion tank.
Therefore thee only way they could produce water leaks at the rear of the block is if the water is spraying from them onto the back of the engine.
I'm at work today so cannot look at my engine to see what this plastic plate is?
If water is definitely coming from that then it needs investigating further (master of the bleedin' obvious! :roll: )
I suspect the coolant level dropping is what has created an airlock in the heater matrix and preventing coolant flowing through that.

Hi enuff_zed, thanks for your input. So it seems that the part that I mentioned previously being attached to the back of the engine block is called a ‘cover plate’. It’s sort of shaped like a vent, one larger and one smaller circle and is sealed on with O rings. See this link (part number 17)

https://www.realoem.com/bmw/enUS/part?id=BZ12-EUR-02-2007-E85-BMW-Z4_20i&mg=11&sg=15&diagId=11_3178&q=11537583666

I will have another check around the area this evening. Blown Head gaskets are usually an internal leak aren’t they?

Would be most unusual to have a head gasket pour water out of the head. Plus it would do it under greater pressure and probably come out as steam. I did see that cover plate on realoem this morning actually. Apart from losing more coolant it looks simple enough to fit new seals.
They are a pig to fill and bleed though. Put the front end up on ramps to make the expansion tank the highest point and fill slowly. Then start the engine and continue to fill. Even then it's 50:50. Maybe worth asking a garage to bleed it using their fancy vacuum systems?

Ah I posted as you responded. Yes I’ve never had so many issues with ‘air locks’ in a coolant system. I had a few horrendous air locks when I first bought the car 4 years ago. In the end I had to park it on a steep hill with the front end up, open the cap, run the engine with my partner pumping the throttle whilst I used a 5L water bottle upside down pushed into the expansion tank. The vacuum it created did the trick though with a volcano of air eventually coming out.

I own a jack now so should be a little easier :lol:

 

[Robin82]

So after further investigations around the rear block I’m
90% sure the leak is coming from this ‘cover plate’ and the. Dripping a few inches further along and off the corner of the engine and onto the exhaust.

I’m not sure of the purpose of this cover plate. It doesn’t seem to serve one :roll:

I should be able to get a small socket wrench in behind the block and the heat shield. Will be a little fiddly but should be ok.

I’m also assuming I have the mother of all air locks in the system too…

While you're in there, pop the two pipes off the heater matrix and blast through with a hose pipe, swapping directions every now and then. It won't shift an airlock, but if nothing has been going through there for a while the sludge will have started to settle. Get it out while you can.

I certainly will give this a go! Thanks!

 

[Robin82]

Unfortunately still not solved completely!!

So an update on the above; cover plate replaced on rear of cylinder head - leak stopped.
Hose replaced on front of cylinder block (top) - leak stopped

I thought that had them covered but no, there is dripping coming from the bottom of the engine block, front drivers side of the block.. it is so difficult to find the source of this.

Any idea’s of potential source? It is very difficult to get any kind of view of this area. I can see no other hose leaks but I’m not sure…

No overheating of the engine at all either. I have noticed water pooling a little in the exhaust however, but I’m probably being paranoid.

 

[enuff_zed]

Drivers side front of the block is the water pump. Could be running down from that?

 

[Robin82]

Yes you could well be right. I should say offside, is this where the pump is located? Maybe a hose that connects to the pump..
I’ll take the splash pan away and have a look from underneath.

Much of a job, changing the pump?

 

[enuff_zed]

Yes you could well be right. I should say offside, is this where the pump is located? Maybe a hose that connects to the pump..
I’ll take the splash pan away and have a look from underneath.

Much of a job, changing the pump?

Yes offside.
Not done one on a 2.0, but it does look fairly straightforward. At least there's plenty of room in there.

 

[Robin82]

Yes you could well be right. I should say offside, is this where the pump is located? Maybe a hose that connects to the pump..
I’ll take the splash pan away and have a look from underneath.

Much of a job, changing the pump?

Yes offside.
Not done one on a 2.0, but it does look fairly straightforward. At least there's plenty of room in there.

Finally got around to taking a proper look with the splash shield removed.
Coolant is pooling, very slowly on the bottom of the pump, then dripping off.. but I can see no direct source for the leak.

I’m assuming this might happen if the gaskets have split/blown within the pump? Hopefully replacing the pump should solve the issue then…

C

 

[enuff_zed]

The hoses that push fit onto the pump have internal o-ring seals. These can dry out, flatten and cause leaks. They come as part of the hose but you may be able to match them from generic ones. Until you get them and the pump off it'll be hard to see exactly where your leak is.

 

[Robin82]

Looks as though there are two parts to the water pump? The coolant seems to be pooling where these two parts meet (no gasket) On RealOEM there is the water pump and the ‘coolant pump’ this latter part connects to the pulley wheel.

I suppose, like you say, no way of telling which bits are knackered until it all comes out.