[moneyposse]

Hi everyone, first time posting.

I've had a coolant leak in my 2007 335i coupe that so far has led me to replace my radiator, then oil filter housing gasket, and then my water pump this past Tuesday (3/24). Tuesday and Wednesday, I was able to drive probably about 270 miles with absolutely no problems - no coolant light, had working heat, and no overheating. Wednesday, however, about halfway into my drive back home from my buddy's garage (90 miles away), my coolant light suddenly came on, followed shortly by the yellow overheating light.

I made it back to my house and put what little amount of antifreeze I had left in my garage. After the water pump job, we just left the bottom engine pan/plate off so that if there was another leak (like now), we'd be able to diagnose it a little better (since I cannot work on my car at home). Anyway, I ran the car for about 5-10 minutes to get that small amount pumped through; no obvious leaks or drips anywhere. The next day (Thursday), I bought another gallon and put it in. My coolant light disappeared but then came on just a few minutes later. I turned the car off and checked the reservoir tank - there was a small amount (clearly not a gallon) still left. I decided to just leave it be while I checked for leaks/drips underneath and in the engine bay.

Friday morning (yesterday) I checked the reservoir tank before work and it was still holding the same amount, and no still nothing on the ground. This is around when I started thinking, what if it's leaking internally somewhere? I got home from work later last night and bought another gallon of antifreeze. Filled the tank to the very top and let it run for probably 15-20 minutes; coolant light was off, engine temp was holding steady, no leaks. Took it for a drive and made it about 20 miles before the coolant light was back on.

Does anybody have any ideas? I tried posting on reddit (my mistake haha) and only got a few responses, mostly suggesting to get a coolant system pressure tester. Anybody think that my coolant is leaking into my oil somehow? That's my current inclination so today I'm thinking of going to get an oil change and having them look for coolant/antifreeze.

[mweisdorfer]

Originally Posted by moneyposse

Hi everyone, first time posting.

I've had a coolant leak in my 2007 335i coupe that so far has led me to replace my radiator, then oil filter housing gasket, and then my water pump this past Tuesday (3/24). Tuesday and Wednesday, I was able to drive probably about 270 miles with absolutely no problems - no coolant light, had working heat, and no overheating. Wednesday, however, about halfway into my drive back home from my buddy's garage (90 miles away), my coolant light suddenly came on, followed shortly by the yellow overheating light.

I made it back to my house and put what little amount of antifreeze I had left in my garage. After the water pump job, we just left the bottom engine pan/plate off so that if there was another leak (like now), we'd be able to diagnose it a little better (since I cannot work on my car at home). Anyway, I ran the car for about 5-10 minutes to get that small amount pumped through; no obvious leaks or drips anywhere. The next day (Thursday), I bought another gallon and put it in. My coolant light disappeared but then came on just a few minutes later. I turned the car off and checked the reservoir tank - there was a small amount (clearly not a gallon) still left. I decided to just leave it be while I checked for leaks/drips underneath and in the engine bay.

Friday morning (yesterday) I checked the reservoir tank before work and it was still holding the same amount, and no still nothing on the ground. This is around when I started thinking, what if it's leaking internally somewhere? I got home from work later last night and bought another gallon of antifreeze. Filled the tank to the very top and let it run for probably 15-20 minutes; coolant light was off, engine temp was holding steady, no leaks. Took it for a drive and made it about 20 miles before the coolant light was back on.

Does anybody have any ideas? I tried posting on reddit (my mistake haha) and only got a few responses, mostly suggesting to get a coolant system pressure tester. Anybody think that my coolant is leaking into my oil somehow? That's my current inclination so today I'm thinking of going to get an oil change and having them look for coolant/antifreeze.

Did you replace all the o-rings on the various connections when you replaced the radiator?

[mweisdorfer]

What does your oil look like?

Frothy? If so, you have an internal leak. Most likely it's from the OFHG.

Use Ultra Black when you do the OFHG. Sand which the OEM gasket in between two beads.

Also, replace the coolant flange , oil temp & coolant temp sensors while you are in there.

Ultra Black takes 24 hours to FULLY cure

[moneyposse]

Originally Posted by mweisdorfer

Did you replace all the o-rings on the various connections when you replaced the radiator?

I had an independent shop do that repair; I have no idea. Invoice for that just says "radiator assembly" with a part number that yields no results.

Originally Posted by mweisdorfer

What does your oil look like?

Frothy? If so, you have an internal leak. Most likely it's from the OFHG.

Use Ultra Black when you do the OFHG. Sand which the OEM gasket in between two beads.

Also, replace the coolant flange , oil temp & coolant temp sensors while you are in there.

Ultra Black takes 24 hours to FULLY cure

Any place that I tried for an oil change today was either closed because of coronavirus or booked with appointments already. Would looking in the engine oil cap help at all? Or is draining the oil the only way to tell since we don't have a physical dipstick?

[clegg]

You could also pull your oil filter and see the condition of the oil.

[mweisdorfer]

Originally Posted by moneyposse

I had an independent shop do that repair; I have no idea. Invoice for that just says "radiator assembly" with a part number that yields no results.

Any place that I tried for an oil change today was either closed because of coronavirus or booked with appointments already. Would looking in the engine oil cap help at all? Or is draining the oil the only way to tell since we don't have a physical dipstick?

Pulling the oil fill cap open could/ should reveal yellow, frothy type oil.

[NGEE]

I'd recommend a pressure test. The kits are not that expensive.

[John 070]

Originally Posted by clegg

You could also pull your oil filter and see the condition of the oil.

I can attest that it's safe to open it. After finishing an oil change, replaying in my mind, I realized that rather than putting the filter in the cap, and screwing the cap in, I put the filter in the OFH, and closed the cap on top of it. I reopened the cap after the fact (having already run the engine and checked for leaks) to make sure everything was ok. I guess technically maybe the two o-rings are opened 1 time more than normally, but what I mean is didn't harm anything.

[moneyposse]

Here's what the top fill cap had inside: