BMW E30 Heater Matrix Hoses Configuration - Right and Wrong way round + how to bleed matrix / remove air-lock

My E30 had little or no hot air from the blower inside the cabin. I have heard it is common for the two hoses running to the heater matrix to be fitted back to front, so the flow of coolant through the core is reversed. This causes air locks and severely reduces the amount of coolant flowing through the heater matrix, thus no hot air. 

The reason these hoses so often get fitted incorrectly is due to their location and the way they look when fitted. It appears obvious that the upper hose (back of cyl.-head to heater) goes to the upper stub on the heater-matrix and the lower hose (side of block to heater) goes to the lower stub on the matrix. The hoses look happier this way round, but the matrix and heater-valve are designed in such a way that flow is interrupted and causes the air-lock. 

The correct way round is actually with the upper hose connected to the lower stub and the lower hose to the upper stub, which does of course appear to be back to front, but is essential for correct flow of coolant round the whole engine, not just the heater-core. The correct and incorrect hose configurations are shown in the pictures below.

RIGHT:

WRONG:

How to Bleed system and remove air-lock from Heater-Matrix:

** This is not the normal air-bleeding process when refilling an empty system with coolant, this process is to bleed a system with the air-lock at the back of the head and / or the heater-matrix full of air. **

1. Ensure heater-matrix hoses are fitted the correct way round, if not swap them over. [You should notice if there is an air-lock that no coolant comes out of the hoses when removed from the matrix and the stubs appear dry].

2. Fully tighten the lower [inlet] hose.

3. Leave the upper hose disconnected from the matrix. 

4. Remove the radiator bottle cap. Assuming the coolant level is up to the halfway / max. mark, there should be some gulps of air and the coolant level should drop slightly in the rad. bottle.

5. Cut the bottom off a 2-litre drinks bottle and fill it with water, holding your hand over the lid.

6. Dump the water from the drinks bottle into the radiator bottle, allowing the weight of water to push the remaining air though the system. Water should start to come out of the upper heater-matrix hose from the head. Block this hose with a finger.

7. Continue to top up the radiator bottle with water until water begins to flow out of the upper stub on the heater matrix and quickly refit the upper hose, which can now be fully tightened.

8. Drain the radiator bottle back down the halfway /max. / fill line.

** You should be good to go, but can now bleed / top-up the system using the usual bleeding procedure if necessary. **

E46 318i - Broken Coolant Hose! [11537572158]

 After about 650 miles in the E46 Touring the radiator light came on. Just the amber warning, to let me know it was getting low, not the red warning when it is running out and I refilled about 1.25 litres of water / coolant to the engine. This seemed about right to me, as I feared it may be using a bit of water and there was plenty in when I bought the car so 1.25L in 650 miles isn't catastrophic and can be lived with.
About two weeks later the radiator light came on again and I dutifully refilled 1.25 litres, but the car had only covered 120 miles so I knew something was now amiss, only for the light to come on yet again after just five miles of my six mile round trip to work. Under the hood with the engine running I could see a huge pool of water in the under-tray and a drip, which after much tracing turned out to be coming from a slim rubber hose that connects to the left side of the cylinder-head [N42 engine]. It was a constant drip, but when I wiggled the hose-end the coolant began to spray round the engine-bay, so here was the culprit. Turns out the hose-connector into the head was completely sheared off, as you can see in the pic, and should extend about half an inch into the housing. The only thing holding any water into the upper engine at all was a single M6 thread screw.

The hose in question was BMW Part No. 11537572158, shown in the diagram connecting the thermostat to the cylinder-head. This is a common fault I am told on N42 and N43 engines, along with several other coolant hoses that have plastic end connectors, particularly in the US where kits can be purchased to convert the brittle plastic ends to aluminium ones. This seemed unnecessary for me, given the cost of a replacement part and the age of the car.

As there are so many coolant hose variants, finding the right used OEM one on eBay and the like can be difficult, but they do pop up. I was able to get a new spurious part through work for just £18, but I'm sure commercial motor factors will not be much more expensive as long as they have stock. Spurious hoses tend to come with a new rubber O-ring fitted. BMW dealerships will charge a premium, but at least fitment is guaranteed and they are revised parts, though these may not come with the rubber O-ring which will also need to be ordered.

E46 Clubsport: Loss of coolant... split radiator!

The Clubsport is starting to become a bit 'whatever next' lately. Amidst the other post new year jobs I forgot to mention the coolant expansion-tank that sits next to the radiator had swelled and split down one side, so a new one was duly fitted.

Last week the sudden loss of coolant returned, with the puddle in the same place under the radiator, but no visible sign of a leak. Nath assumed it to be the radiator-cap, so we pressure tested it in work and it's fine. Then we pressurised the rest of the cooling system and this is what we found - the radiator has burst along the top. A new radiator is going straight in, but the fact remains that something is still pressurising the cooling system and needs to get sorted.

E36 316i Compact: New head-gasket.

Well, it's been a busy month again in Beemer Lab and I've just bought a new house which hasn't helped. Firstly, I finally removed the stuck head-bolts from the E60, got the head off and found where my oil leak is coming from... The lower timing case has a big crack in it! It's too big a job to replace that and do the new piston, so it looks like the 530d does need a new engine after all, what a shame after my £500+ spend.

As there is no E46 progress still, I decided a cheap runaround BMW was needed on a temporary basis so I shelled out a quick £200 on an X-reg E36 316i Compact, again in Titansilver. It has 4 months tax and 10 months MOT so seemed ideal as a stop gap. That was until I went to pick up a fridge and it majorly overheated. After I limped home I found oil in the water, water in the oil and a constant bubbling from the radiator. Blown head gasket then!

I had to use it for 2 weeks in this state, only doing the 2 mile trip to work and no further, but still it was getting to max temp as I pulled up on the drive. The gasket was only £18 off eBay and is FAI. The job only took about 4 hours (oh the joys of working with a single cam!) and it is back on the road and running quite cool so far, though I will need to put it through its paces to find out if it was just a dodgy gasket or if there is a real cooling problem that's caused it.

I will cover the poor E60 and it's future in more detail soon. Oh, and I've also bought a new secondary air-pump or the E46 so watch this space. 3 Beemers and counting...

£18 delivered. eBay FTW still.

By gosh, that looks like some hot oil.

The centre two head-bolts [1 and 2] were finger loose when removed!
This has obviously allowed oil and water to mingle. Blast marks round
the front cylinder show where combustion was stopping water entering the head.
This whole head-gasket swap took about 4 hours, so how
hastily the last one was thrown on is disturbing...

Lots of burnt oil and split gasket over the head, but it cleaned up well.

Think I will leave cleaning the cooling system for another day though. The head is caked with 'rad-weld' type stuff.

Amazingly, after all that overheating, the head is straight as anything! BMW alloy heads are forgiving to say the least.

10 minutes with a razor-blade and the block is good as new. PIston don't look half bad either.

New gasket on. The re-tightening sequence is 30nm, 90 degrees and
another 90 degrees. I wonder if the last guy to work on it only did
the 30nm and forgot about the torque angling?

E21 316: New Thermostat working well.

The coolant problems from this post [Coolant/Radiator Troubleshooting] have been truly rectified with the installation of this new thermostat.

The temp. gauge hasn't risen above halfway since, despite some hard and motorway driving, which is great, but the car seems to take a bit longer than before to reach normal temp. It could mean the thermostat is slightly the wrong temperature range, but both the one I removed and the new one are confirmed 80 CEL, so I think it's likely the car now has a more average heat up time and I'm just not used to it!

PROCESS:

BMW thermostat units are built into tube-housings so replacing them couldn't be simpler, simple pop the hose clamps off each pipe and it pulls straight out.

1. Use a flathead screwdriver to loosen the jubilee-clip holding the lower hose in place on the thermostat, pull the hose clear and allow the coolant to drain from the engine into a container.

2. Loosen the jubilee clip to the top hose on the thermostat and pull the hose clear.

3. Loosen the jubilee clip to the hose on the nearside of the thermostat coming from the coolant-return and pull the thermostat unit clear of the hose.

4. Reverse the process with you're new thermostat.

5. Re-fill the radiator with 3.5-5 litres of coolant. ** It's probably best to back flush the engine and radiator while the hoses are off and the system is drained.

E21 316: M10 Coolant/Radiator Troubleshooting

The car has no overheating issues, it's running like a dream, but the temp. gauge does have a habit of wandering between slightly over normal during slow driving or standing at idle. With cool air blowing into the cabin the needle goes slightly higher again, but never goes above about half way between normal and 3/4, even going uphill or driven hard. On a clear motorway run with lots of cool air the needle drops and sits about the same distance below centre, reaching as low as half way between 1/4 and normal. I'm thinking either a clogged radiator or a stuck thermostat and everyone has backed me up, but I thought I'd take a hard look at it this weekend and try to diagnose the problem in clarity before swapping anything.

Symptoms:

Needle fluctuates between slightly cold and slightly too hot in mixed driving conditions. With heater controls set to hot and the fans turned off temperature fluctuates least, but any attempt to blow air into the cabin, hot or cold, causes the temperature to vary more and only cold air blows regardless of heater setting. 

The radiator is plenty full of coolant, but there doesn't appear to be a lot of circulation. The return pipe from the engine to the radiator is red hot, while the send pipe from the radiator to the engine is cool. This pipe should be cooler than the other, but not this cool, so it looks like the radiator valve is not releasing cooled water once the engine has warmed up. Hot water also flows through the heater-core to warm the air, which would explain why I'm not getting any. 

Diagnosis:

It's definitely looking like a thermostat stuck in the closed position and not releasing water from the radiator, but the pipe to the thermostat, even where it exits the radiator is also cool to the touch. My temp. gauge also doesn't just go up and up, it fluctuates to cool as well, so it could still just be a case of a clogged radiator. Let's hope it's the latter, because the first thing I'll be doing is a full radiator-flush to see if there's an improvement, then changing the thermostat if the problem persists. If this fails, then it could be a new, and expensive, radiator or one of the harder to source temp. sensors or even the water-pump. Hmm.

Flushing:

Went to Halford's this morning and bought a pack of Holt's 2-part RAD-Flush [£6.99] and 2 litres of engine-coolant [£15.98]. Drained the system and found plenty of blue coolant in there and no oil, but quite a bit of rusty sludge. The car holds 7 litres of coolant, but I only got about 5 out of it. I removed the radiator [the hoses are off anyway as there's no drain plug] and gave it a good flush with the hose. A lot of rusty sludge and orange water poured out and the water appeared to contain no coolant at all, but once the water had run clear there was no sign of a blockage. I re-fitted and filled the radiator, it took about 5L of water, and poured in the first stage of RAD-Flush, though I'm not sure how it will flush the system if the thermostat won't release coolant. 

The instructions say to run the car at fast-idle for 30 minutes, but without knowing if there's water pumping round the block I decided to abort if the engine went hotter than normal. I stopped running the engine at 13.5 minutes as the needle started to reach 3/4 on the gauge. A quick check of the radiator hoses revealed the same story - in-hose red hot and out-hose now freezing, so I'm guessing there's no coolant in the engine itself at all now. This means I can no longer drive the car as I have been until the problem is fixed, unless I back-fill the engine with water through some other hose, but it will require draining again anyway when the new thermostat arrives.

Thermostat:
All signs now point to the thermostat. Here's a couple of good checklists posted on eHow to help diagnose a broken thermostat, or other possible causes with similar symptoms - http://www.ehow.com/list_6018650_signs-car-thermostat-broken.html / http://www.ehow.co.uk/list_6018650_signs-car-thermostat-broken.html.
I re-drained the radiator and it ran almost as clear and cold as it went in. A little hot water came from the thermostat side of the hose, but it seemed to be more of the blue coolant mixture. I removed the top hose to the thermostat and about a litre of the warm blue coolant mixture gushed out, another litre coming as I removed the hose in the thermostat's side. It would seem that the radiator hasn't been part of the cooling-system since I've owned the car!
I got the thermostat completely out and immediately I could see it's stuck completely closed to the radiator hose, and only partially open to the bypass valve. Water is being pumped through the thermostat and straight back to the engine and this, along with the non-viscous fan, is the only thing cooling the engine. Quite frankly, I'm amazed the overheating problem hasn't been more severe! I guess with it being summer I never noticed the lack of hot air and not using the cold-air blower kept it close to normal. I could live without the cold-air during a British summer, but as winter rolls around I've noticed that the side-windows are impossible to de-mist. Warmth from the engine itself does de-mist the screen, but as the weather grows colder I can't be sure - best to fix this problem sooner rather than later.
Just bought a new budget thermostat from GSF car-parts on eBay. It's not OEM quality, but it is guaranteed and is much, much cheaper @ £12.50 with free postage, although I paid £20.40 for included next-day delivery, which is still good. I really hope this proves to be the only problem with the cooling!