[PICS] New Coolant Leak - Can't Identify Source

[Umuzidan]

I just finished rebuilding the top end of the engine while doing the timing chain guides. Today after driving about 30 minute I noticed while parked at a store that about 8-12oz of coolant was on the ground behind the driver's side tire. Upon inspection back at my garage I see it dripping from a frame mounted bracket which doesn't appear to have any obvious coolant hoses (or related) near or above it. I'm completely at a loss.

Please help me identify possible sources for the coolant leak.

PIC 1: Here you can see a drop of coolant on the edge of a shield covering below the exhaust manifold. Although I can see it here, it'll mostly drip from the small hole on the black curved frame bar to the left in the picture. I had wiped it away clean before the pic so I know it's a little hard to see the source.


PIC 2: Here's a better picture of the two holes where I found coolant dripping. Again, when I first saw the coolant leak, I could see it actively dripping at a rate of about 1 drop per second, pretty active.


PIC 3: In this pic you can see the coolant where it's dropped on the garage floor. There are two leaks in this picture, please only focus on the larger of the two. The other leak will be addressed in a different thread. You can see it's directly above that black curved frame bar you saw in the above two pics.

[Umuzidan]

Unfortunately I can't tell what type of fluid this is. The picture below shows very clearly where it'll drip from. If I take a good look inside the transmission torque converter opening on the bottom of the transmission, I can see fluid if I look towards the rear of the car. Do torque converters leak like this, or is it something else?

[aom7]

Valley Pan? Rear Heater Hoses or Heater core (which are near the driver side area your describing)? Have you replaced any of those?

EDIT: Since it seems the leak is pretty active, that's actually in your favor. You could run the car, put on some latex gloves then feel around the back of the engine and see what's wet?

[Umuzidan]

Valley Pan? Rear Heater Hoses or Heater core (which are near the driver side area your describing)? Have you replaced any of those?

EDIT: Since it seems the leak is pretty active, that's actually in your favor. You could run the car, put on some latex gloves then feel around the back of the engine and see what's wet?

I just replaced the valley pan and all gaskets on the rear accumulator pipe, as well as the o-rings on the pipes below the intake. I'll check the rear accumulator pipe gasket again. What about the rear engine coolant gasket?

[Mayorchuck]

My money is on one of the coolant hoses back there. I've replaced them on every E38 I've had contact with.

- - - Updated - - -

Merged threads.

[PiotrC70]

If it was the rear accumulator due to an improperly seated gasket, it would be pouring coolant... ask me how I know. :/

[Timm]

MY money is it being the A/C drains and is normal behavior! Switch the A/C off for a while and see if it stops dripping.

[clarkitect]

Those O-rings in the rear coolant accumulator can be fussy and are an obvious weak point even if they were just replaced. Could be any of the previously mentioned things though. A pressure test is key. I made my own rudimentary tester and it works great:


I suspect that drip from the bell housing is residual oil from leaky valve cover gaskets. I had the same thing on mine after I finished the guides, and was worried it was the rear main seal, but the drip went away and is now dry. I'd age that one and keep tabs on it.

[purplecty]

Those O-rings in the rear coolant accumulator can be fussy and are an obvious weak point even if they were just replaced. Could be any of the previously mentioned things though. A pressure test is key. I made my own rudimentary tester and it works great:


I suspect that drip from the bell housing is residual oil from leaky valve cover gaskets. I had the same thing on mine after I finished the guides, and was worried it was the rear main seal, but the drip went away and is now dry. I'd age that one and keep tabs on it.

Write up on that pressure tester you built?

[Umuzidan]

So this morning I went to the garage and found that no coolant had leaked since the car sat overnight. I reached behind the driver's head and put a blue shop towel under the coolant accumulator and found nothing, came out clean and dry.

Also, residual oil under the bellhousing from the rebuild can't be true for me. I never have a valve cover leak. The car has been driven about 100mi since the rebuild and without the bottom engine cover on, so any oil dripping won't be from 100 miles before.

I'm feeling more and more sad that it might be the rear engine coolant gasket. I took apart the rear intake OSV diaphragm for now, so I'll test the coolant leak again when I get the new diaphragm.

[clarkitect]

Write up on that pressure tester you built?

I just drilled through the center of a radiator cap from the junkyard and installed an old tire valve. In order to install the valve I needed to pop off the threaded part to cut the insides out a bit, and shave down the tire valve to get it all back together. I'll do a write up with pix if I have a few mins on Saturday. Pretty handy and was free.

Umuzidan, you'll get it. Just going to be a bit of a battle.

[racer2086]

My gf's 540 has that leak at the bell housing. It looks like the fluid is coming from the transmission on her car. Either the input shaft seal or after talking to Eriksson transmission, they said sometimes the bell housing mounting holes on the front of the transmission have casting porosities that leak. I'm just watching it. Not leaking fast enough to worry about yet.

The coolant leak is tough. My best way of finding coolant leaks is with a very very bright flashlight. You are going to have to climb all over that engine, especially to see in the back.

[purplecty]

My gf's 540 has that leak at the bell housing. It looks like the fluid is coming from the transmission on her car. Either the input shaft seal or after talking to Eriksson transmission, they said sometimes the bell housing mounting holes on the front of the transmission have casting porosities that leak. I'm just watching it. Not leaking fast enough to worry about yet.

The coolant leak is tough. My best way of finding coolant leaks is with a very very bright flashlight. You are going to have to climb all over that engine, especially to see in the back.

I believe my 98 is leaking at the rear coolant gasket which I had replaced when the trans was replaced a few years back... I need to ad coolant every once in a while but there's no way im pulling the trans back out of that car...

[PiotrC70]

I just drilled through the center of a radiator cap from the junkyard and installed an old tire valve. In order to install the valve I needed to pop off the threaded part to cut the insides out a bit, and shave down the tire valve to get it all back together. I'll do a write up with pix if I have a few mins on Saturday. Pretty handy and was free.

Umuzidan, you'll get it. Just going to be a bit of a battle.

It should be noted for anyone wanting to try this that you need to turn your air compressor regulator down to the same pressure seen by the coolant system... which on the e38's I'm hoping someone can chime in with a PSI/bar

[clarkitect]

It should be noted for anyone wanting to try this that you need to turn your air compressor regulator down to the same pressure seen by the coolant system... which on the e38's I'm hoping someone can chime in with a PSI/bar

I have a tire filler (like at the gas station) attachment for my compressor, and pumped it to 21 psi (1.5 bar). Surprised how much air it took to get it that high. Once I filled it I monitored the pressure with a tire pressure tester.

Before I got it to hold air it was really easy to find where it was leaking - you could hear it quite plainly, and I sprayed a little soapy water to verify.

[PiotrC70]

I have a tire filler (like at the gas station) attachment for my compressor, and pumped it to 21 psi (1.5 bar). Surprised how much air it took to get it that high. Once I filled it I monitored the pressure with a tire pressure tester.

Before I got it to hold air it was really easy to find where it was leaking - you could hear it quite plainly, and I sprayed a little soapy water to verify.

Thanks for the clarification. I haven't had the need to pressurize my system since everything is new but didn't want someone to be stupid and dump 90psi of air and wonder why things are leaking.

[clarkitect]

Thanks for the clarification. I haven't had the need to pressurize my system since everything is new but didn't want someone to be stupid and dump 90psi of air and wonder why things are leaking.

I'd do a pressure test after reassembly but before refilling if I did another cooling system overhaul.

[Mark3377]

Wish the OP finished the story by mentioning where the leak was. It could help others (me?) years down the road (now in 2020) and others in the future.

[Grady in Texas]

I've developed the same center/rear of engine leak.

I don't smell/see coolant when at temperature in or out of the car (but leaking fluid is green, feels like coolant and the coolant level drops).
Noticed it my parking garage with the car parked cross-wise to the slope (a trail of coolant about 3' long).
Noticed it less when parked flat.
I've looked around once with a flashlight. I can see a few drops of coolant on the rear of the block but can't (yet) pinpoint the leak source.
The leak is fairly small, it takes about a week for the check coolant light to come on (but I have a short commute).

Grady