Ok, so I finally took my 2010 128i to the dealer because I got sick of having not heat. I was fully prepared to buy a new thermostat or maybe even a heater core. However, here's what the dealer found. With the coolant system under pressure, they found the heater core was clogged. Ok, I can see that. Then they found that the pressure test kept losing pressure. Ultimately, they found pin hole (porosity) leaks on the intake side between cyl #1 and #2 on the block below the intake. WTF!!! I bough this car used with 56,000miles in July. I bet the previous owner used some sort of stop leak chemical to fix the pin holes and in the process clogged the heater core. Heater core replacement sucks but I know it will be clog free and good for quite a while. That's not my worry. Block porosity has me thinking the repair won't last. The dealer fix to the pin holes are to clean and prep the block area and apply a type of epoxy. This would be to the outside wall as there is no access to the inside to complete the repair. Anyone heard of this? I had a 1991 318is with the M42 motor and it had a leak at the head gasket where green coolant ate away the aluminum. But they filled with liquid metal and machined. Not sure about an epoxy repair on the outside of an engine block.
I've never heard of anything like that with BMW's of any vintage - will be interesting to get Charlson's thoughts. I'd be inclined to do my own pressure test since, if the leaks are appearing below the intake, I'd want to confirm it's not a head gasket. I wouldn't jump to assuming the worst from your dealership there, but on the surface I can't help but have some skepticism over such a seemingly-fluke type of issue. I would find having a clogged heater core from someone trying stop leak due to a more-common coolant leak (such as a head gasket leak) more plausible. I think N52's have separate electric water pumps which are relatively short-lived compared to the older mounted-to-the-block type, but @ only 56k, you're just in the mileage where that could happen. If it were a head gasket or something else, then you have to start wondering why at such a relatively low mileage - no way to know if the previous owner had a bad water pump fail early-on for instance (did you get a carfax w/ it?), and it suffered overheating, which might lead to a head gasket leak. Old bimmers when they were iron-block & aluminum head could suffer a warped head if they got badly overheated. Check for freeze plugs, if holes in the block have freeze plugs, I s'pose that could be a potential leak. The engine block metal alloy being so porous so as to leak coolant...? Hmmm...... Heater core's an expensive fix - might be worth, like a Dr., to get a second opinion - see the pinned post in the forums 'Member Introductions' section for several approaches to finding an indy shop in your area if you wish to consider that. Sorry to hear you're having to deal with such problems, however, welcome to the club & forums, and Happy New Year's, notwithstanding!
Oh - hate to have to suggest additional expense, but with all that coolant work, might be worthwhile to replace the electric water pump with the other cooling work.
Thanks for the response! Happy New Year! Car fax was good and it was dealer service. First 4 yrs or 50k included anyways. My apologies if I'm not allowed to cross post... but I did find one other incident like this. 2007 328ix that probably uses the same block. Same porosity. Same area. http://www.bimmerfest.com/forums/showthread.php?t=707034&highlight= I'm heavily leaning away from block replacement and considering the epoxy repair. I do trust my dealer with the pressure test and they will repeat with me there. I'm more concerned on a metallurgical level. The N52 is aluminum but then encased in magnesium alloy. Magnesium and water don't mix. I'm worried that the aluminum had a hole and then got to the magnesium from the inside. Would a epoxy repair work on the magnesium shell? The common repairs I have no issue with and know what to do. Tstat and water pump should be ok with hand felt flow and no codes. Replacement is DIY for those parts for me anyways. Heater core I'd try to DIY reverse flush first before letting someone replace (removal of dash needed). I took the car in because I wanted to be sure it was the heater core.
Just documenting anything I find here for anyone else that may have An issue. Looks like 60k miles and 3 years out of warranty is the sweet spot... http://www.opnlttr.com/letter/my-bmw...ne-55614-miles
I have heard of this issue before but have not seen one in person. It is a defect in the manufacturing of the engine block. The two options for the repair is obviously replace the engine block or you can try to use a epoxy but this could still leak. I would use JB weld for aluminum to try to repair it but it can not be a leak that is under pressure meaning if the coolant is coming out quickly under pressure like a stream this will not work. I would talk to BMW customer service about this and see if they can help at all since you didn't do anything wrong. Since the vehicle is out of warranty they may not but its worth a shot.
