Don't know how many of you buy as close to original quality if possible.
In my case I needed to replace the gearbox heat exchanger on my BMW 535d as the thermostat was failed open causing the engine to overcool. In turn this stops DPF regenerations, overfueling as part of the warm up cycle resulting in crap MPG on top of the other issues.
I had already put BMW main and EGR thermostats in and had to resign myself to do this fiddly skin removing job laying on my drive.
I ended up buying a Hella made by Behr one from Euro's as you could see on the pictures this was what looked to be a BMW part with the label removed and a bit of dremel work to remove any BMW traces, £130 instead of £210 so I went for it. Everything seemed fine but 5 weeks later the temps dropped. I clamped off the pipe and went for a drive, temps back up again!
I was told due to the time fitted it had to go back to Hella for testing before they could refund me, so I bought another.
This lasted 48 hours and the same problem.
this time I phone Hella hella and get through to the product manager for the UK who was quite good to be fair, asked me the obvious questions, how are my other thermostats, have I changed the coolant, what are my temps like etc. He couldn't help so he asked Hella in Germany who asked for the batch number and production date then it all fell quiet.
I decided to arrange an exchange as it was under a week and they agreed, picked up and fitted the new one, drove the car to euro's and the temps were back, return leg, temps were fine.
Decided to go out that night for a drive (play) with the gearbox and engine oil temps up on the laptop, hidden menu on the dash to show coolant.
Everything was going fine, a perfect 87-89 degrees. I give it a bit of stick in 3rd from 30-60 amusing myself at the electrically limited 560nm of torque displayed on the laptop from 1500rpm and call it a day, do a driving miss daisy back in the 50mph zone for 3 miles and happen to look down and the temps 84, then 80, then 79. At this point I feel like driving it into a bridge but instead head back to the bypass and snot it up the slip road, temps climb to 87 then as soon as I hit cruise at 75 then drop off again.
3 heat exchanges with production dates spanning 6 months!
Next day when the engines stone cold (0c outside) I clamp off both coolant lines, unplug the one thermostat side and slowly release the clamp on the connected side and sure enough coolant runs out of what should be a closed thermostat (new ones are closed, so are working ones when the gearbox is cold!)
So here I am again, waiting on BMW to get back to me with a better price so I can go the BMW route in the hope they have a better thermostat inside but who knows, Hella say it is the same one, I say they have a huge problem that no one has spotted up until now as the cars they fit do not have a temp gauge so the average BMW driver will not have a clue, neither will BMW as they do not look for this issue, just the forums I frequent trying to get fuel economy back due to bad thermostats.
Hella have gone quiet on me, I think they know I am right and the current line of thermostats are unable to retract against the failsafe spring.
Yesterday I went to my indy do get the gearbox topped up as I managed in my infinite wisdom to use a TX50 instead of a 8mm bit to try and undo the fill plug, it was a dodgy angle and it looked like a frigging TX50, it fitted so well but then stripped the plug, luckily he is a great mechanic and with my help as he was on his own dropped the exhaust to get access and managed to tap a 8mm in and crack it free, not before giving me the same look my wife gives me when I fiddle with something that was working fine and no longer does!
So I now face another £50 bill from him to top off again when this one fits
Grrrrrrrrr
/rant over.