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!

E21 316: Finally decided on wheels - period Cross-Wires

The gleaming new look of the respray was being let down a bit by the tiny 13x5 steel wheels, so I've been looking for some 15x7 in the right offset [~12mm] to make the car a bit more sure-footed in the twists and give it some real stance. I'd like to have got 8" or 9" wide on the rear, but I think 7 is the maximum for the E21 without arch modification. The question was which way to go with the rims?

First I had my heart set on banded-steel wheels for a ratty deep-dish look and to keep costs down. The stud-pattern is the same as early VW Golfs, so there are plenty of sets around, but the lowest offset I could find was 33mm and that's just too big for an E21 without using spacers, which I am loathe to do without being ready to hack the arches yet. Having my own set made was the only option, but we'd now be talking around £500 and still finding 15" steels with a low enough offset is all but impossible. I even enquired about having the stock 13" steels banded to 7J, which is possible for about £200 unpainted, but they informed me that the band would be in the middle of these wheels, giving the width without the deep-dish look. Calamity! With all avenues now exhausted, it was time to look into alloys...

But what alloys? Modern ones look rubbish on classics and there's still the offset problem, so I found myself limited to ones designed specifically for the old BMW fit. Of the modern rims, ATS Euro Cup are probably the most retro friendly and have the lowest offset at 20mm, but the previous owner had these on my E21 and he says they still rubbed a fair bit. To guarantee a good fitment and do justice to the look of the car I began looking for period alloys from the late '70s and early '80s. The choice is a bit limited and seemed to come down to between the Alpina style multi-spokes, which are done to death, or BBS style cross-wires, so I chose the latter. An original set of BBS in the E21 fitment could be thousands, but thankfully there were several companies at the time making decent one-piecers in a similar style, which are a bit easier to get hold of.

They're still thin on the ground though, so I've been scanning eBay for a couple of months and have finally got hold of a set of Melber light-weight 15x7 with the magic 12mm offset.These are proper German period items, well made and Melber have a good rep. in club-sport circles. Best of all they fit the retro-racer bill perfectly, but were still a bit more than I wanted to spend @ £275. They're well used too and don't include tyres either, but thats for the best as I want to stretch under-sized ones on myself and I'm just glad to finally put my massive wheel conundrum to bed...