[Tthayer5]

I bought this 08 328xi (n52)with 150k miles
It had coolant leaks, misfires in multiple cylinders, and blown cats.
I replaced the spark plugs and ignition coils, replaced the leaking radiator hoses, and I’m about to replace the catylitic converters.
I have no more leaks that I can find, no misfires, no fault codes besides the catylitic converters but I’m very slowly losing coolant.
The blown cats and dropping coolant level makes me think maybe it’s a bad head gasket that caused the cats to go but there’s no misfire, any thoughts ideas?

[Tthayer5]

found other similar posts that pointed me towards the gasket on the oil filter housing, I’ll start there

[335i54n]

if the ofhg has any wetness exterior than for sure oil and coolant mixing internally

also the mickey mouse hose can seep and run down and evaporate if its slow

you can also do a cylinder head block check to test for blown hg and pull the plugs to see if any are super clean

[jsunma]

I'd go with Occam's razor here (the simplest explanation is usually correct) and guess that your issue may be one of a simple coolant leak via bad hoses or something external in the cooling system. While a "bad head gasket" is possible, you'd probably be noticing other issues in terms of idle, foaming oil, or steam in the exhaust.

These cars leak coolant almost as frequently and fervently as they leak oil. Check your hoses and expansion tank before going after more exotic issues such as a bad head gasket. Check and check again. Often cooling system problems result from fixing cooling system problems (i.e. messing with one part of the system in order to fix it will result in another part of the system failing. It's a house of cards.)

By the way, how do you know that your cats are "blown"?

[Tthayer5]

Originally Posted by jsunma

I'd go with Occam's razor here (the simplest explanation is usually correct) and guess that your issue may be one of a simple coolant leak via bad hoses or something external in the cooling system. While a "bad head gasket" is possible, you'd probably be noticing other issues in terms of idle, foaming oil, or steam in the exhaust.

These cars leak coolant almost as frequently and fervently as they leak oil. Check your hoses and expansion tank before going after more exotic issues such as a bad head gasket.

By the way, how do you know that your cats are "blown"?

Because you can hear the rattle coming from them, and because of the codes coming from the cat sensors. And I have checked the coolant hoses, I’ve replaced expansion tank hose, upper radiator hose and the thermostat and can’t visually see any leaks anywhere

[Tthayer5]

It’s just the combination of slowly losing coolant with no noticeable sign of leaks combined with the bad catalytic converter that would typically point me towards an internal leak not an external.
I Prob won’t have time to dig into this until end of week but illl update what I find.
I’ll drain and inspect the oil(need to replace oil sensor anyway) and inspect ofhg and Mickey mouse hose and I should prob degrease and wash out entire engine bay to make diagnosing any points of failure easier.

[Tthayer5]

(Just an update in case anyone comes across this thread with similar scenario)

I checked out the Mickey Mouse hose/flange and found no signs of leaks, checked the ofhg again didn’t find anything. I replaced the oil sensor abd found it’s also losing oil, cleaned around the exterior of the head gasket and after a short drive found there was oil slowly seeping out pretty much all around.

So I guess even though the car seems to be running fine and there’s no oil in my coolant and no coolant in my oil I do in fact have a blown head gasket with no other symptoms

[rararat4]

Sorry, this is an old thread but.. I also have a small coolant leak. Since last summer, I drove maybe 8k kms and lost 300ml of coolant during that time.

Of course the oil filter housing gasket is a suspect. I changed it three times. The last time I finally got the Elring part no. 632090 and it seems to be holding even though the metal surfaces under the rubber around the coolant opening were pitted. I think the FPM-PX material is superior even to the original BMW rubber.

So to get to the point, in my case or in the case of Tthayer5, would an oil analysis detect coolant in oil if the quantity of coolant is small?

[e90yyc]

rararat4 I am currently in a similar boat to you, but believe I’ve traced mine to a leaking heater core. Not 100% certain just yet though.

I added UV dye to my coolant earlier this week and will check the core this weekend.

I would think that 300 ml of coolant loss over the course of 8k kms would result in some milk on the underside of your oil filler cap if the leak was internal, but I may be wrong.

[rararat4]

I am not seeing anything untoward in oil. I did an oil analysis some time back which came with a clean bill of oil health. That's why I asked the question. Actually I looked now at the radiator and I seem to have a dried slick of something faint and crusty just under the fan.

Too bad about your heater core. I finally changed the AC evaporator last summer after some 12 years of misery. While I was there I could have changed the heater core but one look at it and the new one from Valeo which is supposedly OE but now made in China and I left the original in. It was pristine. Maybe yours is too.

[e90yyc]

Sorry to sidetrack this, but how was evap job? As much of a grind as it looks?

Honestly, if I go in to do my core I’ll prob change the evaporator again. Was done about 160k kms ago by PO at dealer. Not sure if the the evaporator part was revised to led to early failure, but I struggle to think of doing this job twice… And then I’ll also do my compressor because it’s noisy and the system will be opened anyway. Ugh.

Here’s what my heater core looks like. No UV dye in system at this point but am using UV light in the one pic.

Back to the matter at hand: Is your rad original? Have you tried pressure testing the system and looking for leaks while under pressure? (I know it’s a small leak so whether pressurizing it would help, I can’t say…)

Edit: Not sure if I have Valeo or Denso, but I’m with you on avoiding the made-in-China part. No way the original part was made in China… Hoping I’ve got Denso (Japan, and less than half the cost), but if not I’ll opt for the German-made ACM part or just bite the bullet and go Genuine. Not gonna be chintzy on this one; the labour is the whole deal…

[rararat4]

Yes, the evaporator job is lengthy. I have my age and don't like to overwork myself so it took me, 5 or 6 days but, a) there is nothing really tricky in it, b) there are two videos that are really good so if you take it slow it will work. So long as you don't force anything it all works out. I took my time because when I get tired, I start making mistakes. It is good to go to PNP and take one of the dashboards there apart for practice. I think I broke one tab somewhere on a piece of trim near the rear vents but then I found the piece at PnP and all is well.

I am also hoping that the newer version of the evaporator is improved. The current one on realOEM is the third version. So don't hold your breath, Valeo can mess up an improvement. I mean they ended the second version for a reason. Incidentally while the North American 328i's have the Valeo evap, the Canadian 323i's had the Denso and pretty much escaped the evaporator disaster that these otherwise nice cars were plagued with. I see lots of older BMW's driving with with open windows in summer. Shame on BMW.

I also changed the compressor and the funny story here is that I bought a brand new Denso compressor from Rockauto but then went to PNP and pulled a used one for about 60CAD. I then installed the used one. It works like a charm. But, before recharging I added a few oz of PAG oil. The problem is that depending where you go to recharge, you may not only get the wrong PAG oil but you may not get enough. There is a drain plug on the Denso compressor that is there specifically for adding the PAG oil. It is in a very awkward place. I do not see shops adding PAG oil through that plug. They have all been telling me that the machine they use adds oil at the right ratio of refrigerant to oil. Well, my compressor always made some noise after recharge. The new one is very quiet. Maybe it is better than mine was but it also got more PAG oil.

When you buy a new compressor, the little piece of documentation that comes with it is not clear enough where the drain plug is. It does not say how much PAG oil to add. There is a procedure there which you are supposed to follow that says drain the PAG oil from your old compressor and add the same amount to the new one. What a piece of hog.... When your evaporator leaks, it also leaks PAG oil. So then I had to call Denso or maybe email them and they told me how much to put in the compressor when the circuit is dry.

The black wedge shapes on your heater core are there under the UV light so there may be a problem there. Is there a way to go deeper in with some other camera? Also since your flush did make a difference the core might be partially obstructed still. But the point someone made that you do not smell coolant in the cabin argues against a leak there. Sorry, but no certainties here.

My radiator is original. I am now trying to discover how to pressure test it. Or maybe dye is the answer? I have a bit of time to figure it out. I am not going to rip it all apart in winter.

[mainbearing]

I figured Valeo was the problem, as the few tear down photos on the web were all Valeo evaporators.

When I replaced the noisy blower motor it was made by Valeo. So I am pretty sure the Valeo trash is in the evap housing, as the whole lousy HVAC unit likely was made by Valeo.

[e90yyc]

Originally Posted by mainbearing

I figured Valeo was the problem, as the few tear down photos on the web were all Valeo evaporators.

When I replaced the noisy blower motor it was made by Valeo. So I am pretty sure the Valeo trash is in the evap housing, as the whole lousy HVAC unit likely was made by Valeo.

Ah interesting. So despite procedures saying it’s necessary to confirm whether you have Denso or Valeo, what you’re saying is that having a Valeo evaporator is more or less guaranteed for North American with auto climate (as rararat4 mentioned)? I’m making the assumption that 323s sold in Canada had a lower climate control spec, but I might be wrong. I’ll check mine to be sure, but that’s interesting.

I thought Valeo was decent but it does seem the blower and apparently also the evaporator aren’t so great…

Blower may be less their fault and more a function of BMW’s choice of orientation though, I suppose.

Also disappointing that the German-made part is no longer available. Valeo blower is now made in China…

[rararat4]

If I may, a question to e90yyc: Is your second evaporator holding? 160k kms must have been quite a few years back. The third version of the evaporator started in 2012 so likely you have the newest.

[lowrydr310]

Originally Posted by e90yyc

Back to the matter at hand: Is your rad original? Have you tried pressure testing the system and looking for leaks while under pressure? (I know it’s a small leak so whether pressurizing it would help, I can’t say…)

You guys with the slow coolant loss, have you swapped coolant reservoirs recently? If so, what brand did you use?

The seam of the original coolant reservoir on my 335 started leaking and I replaced it with a Rein part, and ever since then I've been losing about 200ml of coolant every 4 weeks or so. I eventually traced the loss to the coolant reservoir cap, it's not holding pressure and there's dry coolant residue around the outside of it.

I swapped the cap with the OEM BMW cap from my other E90 and it is also leaking, so I measured the opening of the reservoir and sure enough that Rein reservoir is a larger diameter so the caps don't seal properly.

Just trying to share some additional insight, something else to check.

[e90yyc]

Originally Posted by lowrydr310

You guys with the slow coolant loss, have you swapped coolant reservoirs recently? If so, what brand did you use?

The seam of the original coolant reservoir on my 335 started leaking and I replaced it with a Rein part, and ever since then I've been losing about 200ml of coolant every 4 weeks or so. I eventually traced the loss to the coolant reservoir cap, it's not holding pressure and there's dry coolant residue around the outside of it.

I swapped the cap with the OEM BMW cap from my other E90 and it is also leaking, so I measured the opening of the reservoir and sure enough that Rein reservoir is a larger diameter so the caps don't seal properly.

Just trying to share some additional insight, something else to check.

Funny you mention the overflow tank…

I pressure tested my car over the past two days. At minimum, the ear clamp holding my coolant overflow line to the engine/rad coolant hose (driver side) was under-crimped. It’s since been fixed. The UV dye made this dead easy to find at least…

Still thinking there may be a second leak, and that it could be the seam at the overflow tank. I plan to break out some soapy water, since I think the seam sits above the fluid level (not certain though).

I know this isn’t a regular failure item on N52s though.

If I replace, I’ll prob go genuine. I couldn’t find any good OE options and would rather just stick with what’s lasted this long.

Is the Rein part okay otherwise?

[lowrydr310]

Originally Posted by e90yyc

Is the Rein part okay otherwise?

Besides the neck being too big and not sealing, yeah! I'm replacing it... I can feel when I twist the cap(s) down that the Rein tank isn't sealing. The OEM BMW tank on my 330 is as good as it gets; both the BMW cap and Febi-Bilstein cap from the 335 seal perfectly on the BMW tank. I just got a UV flashlight, so maybe I'll try the dye to see if there are any other leaks.

Genuine BMW is $160, Mahle/Behr is $60. Mahle/Behr is allegedly the OE supplier, but interestingly FCP has shown this out of stock. I wonder if they also ran into issues with fitment of these tanks and quietly stopped restocking them?

[e90yyc]

lowrydr310

Thanks for the details! And yeah the dye works well.

It’s kind of a bummer but the E90 is finally at that age where parts that were once available are slowly going away. I haven’t done any serious parts shopping lately, other than coolant system stuff, but I have noticed that PS pump and blower motor are no longer available as OE. PS pump was a few years ago now I think, and blower more recently. Technically blower motor is still available from Valeo, but it’s now made in China… not Germany.

There seem to be other OE parts on FCP that are now made in China. Not sure why they still label them OE, but whatever. Not once in my life have I laid hands on a Chinese part and found it superior or even equivalent to one from Germany. They’re not all bad, but IMO still inferior.

I swear a German-made OE coolant overflow tank was available last time I looked… but that woulda been a few years ago.