Coolant Pressure Test Kit that fits E46 M3

[JustAWhisper]

Hello all,

First post on this new forum. Apparently M3Forum died, which is too bad since I'm sure the answer I'm looking for would be buried in there somewhere.

I'm attempting to diagnose a possible coolant leak. I've been getting minor transient temperature fluctuations (no higher than about 104C) in my coolant temp indication. I initially suspected it was electrical because I've replaced water pump, thermostat, and radiator, and lower radiator hose sensor within the last couple years and I'm also getting incorrect readings in the car for outside ambient temperature.

However, inspection under the hood shows evidence of dried antifreeze on the front of the engine case and on the pulley shafts. Coolant level is unchanged and nothing is making it's way to the undertray without evaporating, so the leak is not significant, but I would prefer to fix.

I theorize that the thermostat seal has gone bad prematurely somehow (perhaps I didn't do a good job of installing it?) and is allowing trace amounts of coolant to sneak out, causing enough of a pressure fluctuation to show up in the coolant temp. However, because I'm not sure I want to run a coolant pressure test. I haven't done this before because previous leaks were easily attributable to the water pump and radiator going bad. I read that the rental kits at Autozone and whatnot don't have fittings for BMW, so I went ahead and bought the Pittsburgh Harbor Freight kit. Unfortunately, none of the fittings appear to fit the M3, either, despite it having two that were supposedly for BMW's.

Anyone have any recommendations? Thoughts on the possible coolant leak?

[heinzboehmer]

Is there dried coolant on your hood/airbox/driver's side plastic shroud? If so then chances are coolant is seeping past the water pumo bearing. Shine a flashlight at the back of the water pump pulley to check for dried coolant there too.

[JustAWhisper]

There is some, but it's hard to tell if it's a new leak. I replaced the water pump a while back when it was leaking in that same area.

I managed to find an adapter that fits the M3 expansion tank. I apparently missed it the first time, but going through the entire set again allowed me to find one that works.

So far, after poking around for about an hour now, the pressure has held almost perfectly with no observable drop on the gauge and I haven't found any apparent leaks. Just more bits of dried antifreeze which may or may not be new. While I was able to catch my water pump when it was only generating a small leak, my radiator dumped half of its capacity all over the engine bay when it went unexpectedly last year. I'm still finding bits of dried antifreeze in various nooks and crannies from that, making it hard to identify what's new and what's old.

Incidentally, I saw the other thread discussing A/C and alternator as other possible sources of overheating. I guess that's something else I can look into.

[WOLFN8TR]

It could be one of the orings leaking on the hard pipes to the water pump or the Oring/gasket on the water pump. I refreshed my entire cooling system and had an issue with the small orings that were sent from ECSTUNING. One was too small causing an air leak when running and a small drip when off. This could be the same issue your dealing with.

Let me know if you want a set of Hi-Temp Orings for the Cooking System.
Link is in my Signature.

[JustAWhisper]

Yeah, it certainly could be an O-ring somewhere. It might also be one of the main coolant hoses to the radiator, as I noticed they're starting to swell a little. But whatever it is must be very small and intermittent, and without a smoking gun I don't want to start tearing everything apart.

I cleaned up several of the dried antifreeze spots behind the pulleys that I discovered today so I can at least start from a clean slate when monitoring those specific areas. I'll inspect and pressure test periodically to see if I can isolate the area where it's coming from. If there's a small leak somewhere, it'll get worse and become easier to identify. The cooling system is not working optimally, but it doesn't appear like it's about to blow up and at 104C I'm not worried about a head gasket popping. It's not ideal, but the summer is ending and I finally have another car I can drive (I was temporarily daily driving this car at the height of Vegas summer, which is probably the hardest the cooling system has ever had to work in its life), so at least the car is getting a bit of a break.

[WOLFN8TR]

I know the feeling, DD my M3 thru three Hot Vegas summers. The 115+ days are brutal on cars out here!

[8000RPM]

Yeah, it certainly could be an O-ring somewhere. It might also be one of the main coolant hoses to the radiator, as I noticed they're starting to swell a little. But whatever it is must be very small and intermittent, and without a smoking gun I don't want to start tearing everything apart.

I cleaned up several of the dried antifreeze spots behind the pulleys that I discovered today so I can at least start from a clean slate when monitoring those specific areas. I'll inspect and pressure test periodically to see if I can isolate the area where it's coming from. If there's a small leak somewhere, it'll get worse and become easier to identify. The cooling system is not working optimally, but it doesn't appear like it's about to blow up and at 104C I'm not worried about a head gasket popping. It's not ideal, but the summer is ending and I finally have another car I can drive (I was temporarily daily driving this car at the height of Vegas summer, which is probably the hardest the cooling system has ever had to work in its life), so at least the car is getting a bit of a break.

If you see crust behind the pulley its probably the water pump. I was having issues with my cooling system but after a full refresh including the radiator, no more issues. Today, 111 sitting in traffic, going up hills, under load, etc, temp gauge doesn’t move from the middle. If yours doesn’t sit in the middle, something is wrong.

If the radiator is original, that’s a strong possibility. I would not have thought my radiator was the problem but after chasing all the usual suspects, that ended up being the problem. My coolant was even nice and clean coming out.