Beware! This company has stellar reviews, but in my case it was incompetent and irresponsible act on their part. I used them for some other repairs on my 2009 BMW 550i with good results, except paying much more than I'd pay in shops of the same expertise due to their unjustified hourly rate of $140/hour. In my case their expertise resulted in scrapping and replacing the engine.
Here is my story.
My car had an issue with leaking coolant from the day I bought it in Mar 2019. It was a small leak causing maybe a cup of coolant to be added per couple of weeks. The low coolant icon always was coming up on a dashboard alerting me that the coolant level in an expansion tank was slightly dropping. At one time I let my friend to use this car for an extended period of time. She didn't catch those icons which normally stay on only for a several seconds resulting in engine overheating and expansion tank bursting up. The car was towed to my local mechanic who replaced that expansion tank and additionally replacing water pump and outlet pipe assembly. Repair cost ~$1400. After that repair I was still experiencing coolant leak at the same rate as before. The car was brought back to the shop and the entire system was checked under the pressure and has shown no leak. I decided to live with this leak for a while, since it wasn't a major inconvenience. But finally I wanted to fix this issue and came to Renn Haus as to "experts" of BMW an ultimate leaking machine. They told me that the water pump outlet pipe system (repaired a several months ago) needs to be replaced with the newer design, superior to the old one. The tag price $2500. I was surprised, but trusted their diagnosis and let it do. A day later they called to tell me more work needs to be done (like they shouldn't know this for the repair which is typical for this vehicle as they told me). $700 extra. After a couple of days they called me and said that during the after repair car test the expansion tank bursted on them, so I need to pay for the tank $100. Asking why it bursted they said, it happens(?). Recently replaced tank bursted w/out any specific reason?
There are only two case, which may cause it, either they didn't put enough coolant, if any or the coolant leaked out from the system during the test drive causing engine overheat and over pressure. Total cost of coolant leak repair was over $3,300. I took car back with broken wallet, but with hope of getting rid of the issue. After driving it for a few days I experienced an intermittent misfire on 4th cylinder. I haven't related it to the coolant repair thinking more like spark plug or ignition coil failure. I ordered set of spark plugs and coils and a few days later replaced them. It was late evening. Next day morning I wanted to check the car performance. Started the engine and waited shortly for my wife to join. Suddenly the car started to shake and within seconds I heard the terrible knocking sound in engine. I was so rapid that I couldn't turn the ignition off. Engine stalled. Something mechanically broke and I couldn't start the engine again. The low coolant icon appeared on dashboard. I opened the expansion tank - it was empty. Not a drop of coolant on the driveway, though. Interestingly there was no any warning of low coolant when I was starting the engine. I poured a gallon of coolant into the expansion tank and the sensor floater came up slightly. I was hoping that after there is some coolant in the system the car may start. But not. Then I checked the oil dipstick and it was covered with a white foam.
I called Renn Haus and they courteously towed my car to their place. Before the towing hooked up the car I looked into the expansion tank and it was empty again. The gallon of coolant disappeared. Where did it go and how? No coolant on the driveway.
Renn Haus diagnosed again a gave me a grave sentence for the engine. It's a scrap due to the engine head gasket blew up on 4th (or 8th depending on counting) cylinder allowing coolant to flow into the oil and consequently causing engine to get destroyed by the lack of lubrication and cooling.
This is something you don't want to hear from the BMW experts after making $3,300 unnecessary repair for the water pump pipe. That pipe system was fine being tested successfully before. The cause for a slight coolant leak was that gasket. Now the question of coolant sensor comes up as a major factor in this failure. The coolant sensor is a part of expansion tank replaced by Renn Haus. Why wasn't it warning about a low coolant? It was always before warning me about the lowering of coolant level. It was either wrongly reconnected after repair or faulty. Either way it's a fault of the repair, since the expansion tank with the sensor was a part of this repair. The next question regards the gallon of coolant I poured into the expansion tank after engine stalled. It couldn't flow from the expansion tank to the oil pan through the gap in the head gasket. The gasket is at higher elevation. It could only flow through the water pump pipe repaired in this case. It is lower than the expansion tank. It points that the repair done by Renn Haus was faulty and allowed the coolant system to empty out. Also the fact that it disappeared quickly points out to the reason not related to the head gasket which was sipping, not flowing.
So much for the Renn Haus expertise providing a wrong diagnosis, taking thousands of dollars for unnecessary repair and washing their hands of the responsibility for the expenses related to engine replacement. I am not their conscience, which if they have one it may make them feel like a crook, but it may be a case for the litigation. The cost of their mistakes is enormous.
I apologize for the long review. I think this case is worth to be heard.