Coolant woes..
 

So my wife's X5 M54 has been leaking coolant lately from the drivers side front. I replaced the hoses, expansion tank, and automatic transmission thermostat. The leak still occurs. It leaks down to a point overnight and won't leak anymore. I add about a quart of coolant, bleed it, and the car is fine until it has to sit overnight again. Then it leaks down 1 quart and never more than a quart. After it has leaked, the heater doesn't work well even though the temp needle is rock solid in the middle.

I've looked and can't figure where the French toast the coolant is leaking from! Is there anything else that leaks around there or is it probably a ninja hole in the radiator? Any suggestions help!

my bet is the water pump is leaking from the weep hole

The water pump much closer to the middle of the motor though. I've never heard of the weep hole.. What's that?


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The small auxiliary water pump is on the drivers side, close to the radiator. All plastic, so they crack. The heater valves are on the drivers side firewall near the strut tower. Also have plastic parts.

If you really can't find it, get a uv dye kit and put some dye in the coolant.

A word of caution, it took many (like 10) fill, warm up, drain, repeat cycles to get the dye out when I was done, so I would suggest using 1/10 bottle of dye to start and not the whole thing. I did use straight deionized water for this flush and then filled with proper coolant at the end.

How about just getting a pressure tester and doing it that way.

I think it's pretty obvious we are losing pressure so not sure what that would help.

I'm mostly looking for items outside what I mentioned in that area that can fail.

The pressure tested will reveal your leak. Top off the coolant, hook up the pressure tester, take it up to 15-20psi (should be good) and start looking around for your leak.

There are a bunch of plastic parts at the bottom of the rad that could be your culprit... as well as numerous hoses.

http://www.realoem.com/bmw/images/diag_3ebw.png

http://www.realoem.com/bmw/images/diag_3sl1.png

:iagree:

Ah, increase the pressure - Great idea. Thanks! Looks like that's my Saturday chore..

When this all started my wife told me she heard a pop! noise followed by some spraying of coolant, but just a quart. That's why I went straight for the expansion tank and the "usual culprits" in that area as I've experienced on my E46's. Even if they were ok, we're at 100k and needed replaced regardless.

Is there anything else down in that area that has been known to go POP?

Sounds like the pressure hits the 2 bar max on the expansion tank and vents the excess coolant to lower the pressure - I would probably park it until you can fix the problem

Agree with the venting idea - And that could be an early sign of a head gasket leak. If you have or can get a combustion gas leak test (it's a kit), check the coolant for combustion gas.

We have it parked. The wife stays at home so it won't be driving anywhere.

Could you please you elaborate more on why the pressure is building and where it's being vented to?

It vents out the expansion tank cap, there is a pressure relief valve of 2 bar built into the cap. The venting is a byproduct of some other problem, under normal system pressures and operation it should not be building up 2 bar of pressure to vent - so that is why you need to pressure test the system and see where it is leaking from.

When you leak out coolant you have too much air in the system which builds up pressure with the temperature, thus it vents. So find out why you are leaking, have it filled/bled etc to correct coolant level, and then you shouldn't be hearing any more "pop" and spraying coolant, which is coming from your expansion tank cap.

I also suggest getting a 1.4 bar cap from an E30 BMW. Makes it more likely that the cap will be the pop, and not some hose. You can search previous discussions on the matter.

You could have popped something just by getting the mixture wrong.

Thanks for all the insight guys, it's very helpful. I'll pull the skid plate off this weekend and pressure test. Hopefully it's not something horrific

Keep posting I have two of these cars and need to have my fixit solutions at the ready.


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Will do!

Please save time and money and buy a pressure tester kit
Radiator Pressure Tester Kit

What you do is make sure the engine if full of antifreeze/water. Engine cold remove cap and install the pressure tester pump...pump it up to the cap pressure 10psi? you don't need much. What happens is the air pressure will force the coolant out where it is leaking and in less than 5 mins you will see where the exact leak is no matter how small or large. If the gauge stays at the pressure you stopped at and does not move for 10mins than you have no leak..in that case I would let sit overnight with pressure gauge at 10 PSI.

You have replace the common parts and that's fine but these X5's anything can leak after that. I have an 02 4.4 and I've replace and I mean EVERY coolant hose-pipe fitting radiator-water pump on the car. I have a 06 3.0 I just replaced the water pump and upper and lower hose and rest is fine.

BMW used some really shit plastic and rubber in these X5's and the deteriorate big time or time. To use my 02 as an example, 14 years all rubber and plastic goes....already hanged my cracked plastic timing chain guides.

So save money and time, buy a pressure tester.

Not really.

So our system based on the rating on expansion tank is 2 BAR. 10 psi would be roughly .7 BAR. You need to pump that sucker up to about 29 PSI to reach the limit of the cooling system. Yea, I know, that is insane psi for any car. And our cooling systems really don't reach that limit normally.

I suggest you go higher than 10 psi to test. Like 20.

And as stated prior consider switching that 2 bar cap to something like 1.4 e30 BMW cap or the 1.2 cap. At least give yourself a fighting chance before blowing hoses off on a 10 year old car when over some issue causes over pressure.

There are a lot of bad info on message boards and the internet. Take it from a ex tech. Only pump your system up to the cap pressure limit. Any higher and you can do damage to your system especially blowing the seal on the water pump or damaging a worn radiator, remember these cars are old.

Most coolant leaks will start to leak at just 5 psi.

You may have missed what I stated. If you pump your x5 system to 2 bar, I guarantee you will blow something.

Our cooling system never hits 2 bar, thus I stated that you should not even go that high up in pressuring it up.

It seems the safe way to perform the test is to start with lower pressure and gradually increase it. Thus I would initially pump no more than 10 psi. If I didn't discover any leaks then perhaps go a little higher. This seems a reasonable means to test while reducing the chance of damage due to over pressure. Or is there something I'm missing? As for the pressure numbers I'm using what others have provided. I make no claim to know what are reasonable numbers to use.

Good logic. I only say go to 15 - 20 PSI, because you may actually have a problem that brings your system to that high of a pressure, and only causes coolant loss at that point. And since the relief cap is at 2 bar, which is 29 PSI, every other component will fail before the cap relieves pressure.

Yea you may find a leak at 10 psi. Just make sure you test it again at a higher pressure to make sure nothing else is leaking.

I agree... and suggested that range myself. :thumbup:

Curious though... what is normal operating pressure after reaching operating temperature?

Pretty sure under 1 BAR.

I've been running with the 1.4 bar e30 cap for over 2 years now. Not one issue. I only burped it once when I overfilled it. Otherwise all good.

Here is a good read on the subject, and you can buy the 1.2 cap from them.
https://www.germanautosolutions.com/...12_bar_cap.php

Quite popular cap on the e39 forums.

I'm confused. How is it possible that it leaks AND holds pressure well enough that the needle stays in the middle of the scale?

If it leaks, then it has to NOT hold pressure, that's why it is leaking. I can understand that you can't find where it leaks from, but I cannot understand the objection to a leak-down test. I have to admit, I'm not sure what such a test will tell you, but it should tell you that the system has lost integrity and does not hold coolant any longer.

Coolant is collected at the bottom of the radiator and fed into the engine where it circulates, then is expelled into the top of the radiator where it falls to the bottom and cools, then starts over again. Just because you have lost a quart of coolant, the coolant that remains should still flow to the heater to heat the cabin.

My guess is that you have, among other issues, a clogged radiator, although this should also cause over heating troubles. Restricted coolant flow can affect coolant that goes to the heater core, and this will result in cold temps in the cabin. A clogged heater core will also give poor heating performance inside the car, but not affect cooling of the engine.

My point is, the loss of a quart of coolant should not be the reason why the heater blows cold. And, the repeated loss of coolant is either onto the ground, or out the tailpipe. Your description of the symptom set is not clear that the coolant is in a puddle under the car, or simply missing into thin air.

I believe the Bentleys manual says you should pressurize your system to 21.8 psi and it should be held for 2 minutes. It should not lose more than 10 percent (if my memory serves)of its pressure in that time frame in those 2 minutes. I think mine dropped from 21.8 to 21.5. My two cents worth. I will check my manual after I get off work.

Hey guys, take this from some who owns a pressure tester and did this for a living. All you need is 5psi to 10psi and the leak will appear...you never want to exceed cap pressure, no need to get even close. You guys are over beating this dead horse. This is a very simple-simple procedure.

I wish I didn't keep getting updated emails on this post.

Sorry to offend. Just trying to help.

:iagree:

A quick pressurization with a pressure tester will show where the leak is. Think of a soda can. If there is a hole in it it will start leaking the second you shake the can causing an increase in pressure. If there is a large enough leak you will never get to any higher pressure as it will bleed out the second you pump up the pressure tester.

Sample Pressure tester (yes, you will need an adapter to use on any Euro model)

Adapter: Stant 12030 Threaded Radiator Cooling System Tester Adapter for all early BMWs like ours.

If the coolant is full when you shut if off then any pressure 'leaking' will occur in the next few minutes and with that magnitude of coolant loss you should be able to see the source though you may have to remove the plastic covering under the engine. Coolant will leave a white residue and is almost always visible especially on plastic parts such as on the expansion tank if the cap is involved. A bright white LED flashlight will highlight the residue. I would start with areas that are above the level of coolant when it is a quart low.

There are symptoms associated with a blow head gasket or other internal problems associated with coolant. Engine runs rough, loss of power, sweet smelling white smoke out the back, indication of coolant or oil in the coolant.

I am not suggesting a pressure test won't be beneficial. I am saying that I have never needed to resort to a pressure test to find any type of coolant leak in the last 5 decades. I love an excuse to buy new tools but as few times as I have had a coolant leak over the years I wouldn't suggest buying one. If you want go that route, I would take a trip to local radiator shop, or almost any chain type auto repair shop.

I believe the leak test being referring to is not a leak-down test but rather a pressure test to reveal a leak. Leak-down test is a test to help determine the state of the engine.

Like BCredliner mentioned, coolant leaks are quite obvious and will leave behind a stain that can be traced to the source. Run the vehicle up on some ramps, lay on your back and look up. Follow the drips to the source. If you need a larger stream to determine the source then think about a coolant pressure tester. NOTE: This is a simple hand pump that adds a little pressure to the cooling system via the overflow/expansion tank which in turns pressurizes the entire cooling system. It NOT rocket science, guys.

Common sources: The normal stuff, Expansion tank, Thermostat, major hoses to the Rad, the Radiator itself, heater hoses, heater control valves, and the heater hoses themselves. All will go "POP" when pressurized and then crack.

Heater "BYpass Valve" (AKA heater control valve)
Genuine BMW Heater Bypass Valve 64128374995 - Free Shipping

Note: All plastic + 10 years who knows what is left....

A leak down test induces air into a particular cylinder to test for loss of pressure due to valves, heads, head gasket, rings and pistons. The source of the loss of pressure could be allowing coolant to leak but I wouldn't do a leak down test unless there were symptoms such as, loss of power, missing, oil in water or water in oil.

A coolant leak can be caused by pressure that only exceeds the cap release point when the engine is first turned off. This is due to percolating that can happen when there is no cooling benefit such as an auxiliary fan that does not run for a minute or two.

Heater not blowing hot is not always low coolant but when there is also loss of significant coolant it is often the case.

What about exhaust leaking into the cooling system from a blown head gasket or cracked/warped head? I've had an E36 and an E30 with this problem... never overheated and ran great, but leaked exhaust into the coolant system causing loss of coolant through the vent hose.

The above is kind of a worst case scenario and I wouldn't jump to that conclusion or anything OP. First things first, find out where the coolant is going. Pressure test will reveal that. If you don't see any external leaks (hopefully you do), and the system won't hold pressure... time to pull the plugs and see if you have coolant going into the combustion chambers.

Yes, that can happen though with this amount of lost coolant it is a long shot. Also, Recall I said in an earlier post--if the cooling system is full when you turn the engine off. In this case since the coolant loss seems to be overnight there are no fumes to force coolant anywhere when the engine is not running.

Gotcha. Forgot he was seeing coolant loss only overnight. Weird there is no visible coolant with that much loss every night...

Get that pressure tester and find out where that coolant is going. :thumbup:

UPDATE!!

Problems solved. I wanted to come back and let you guys know what happend.

It turned out when I installed the new expansion tank, I made a mistake. Well me or shotty products, who knows. On the bottom of the ET there is a large opening that has a rubber seal, which is held in by a conical piece of plastic like a washer. On mine, for some reason, this plastic piece fell down slightly and covered the grooves the wire clip slips into when you install to hold it onto the hose. This cause the expansion tank to basically just be sitting there and not clipped in place. It was in there good enough to not cause issues but resulted in a slow leak. I couldn't see anything just laying under the car until I added some pressure with the pressure tester.

Corrected this, reassembled, added coolant, bled, checked oil for coolant or discoloration (just in case), and all was well. I feel like an idiot but i'm happy now it's all done!

Thank you everyone for the tips/tricks/help.

Success is a great feeling. Congrats!:thumbup:

If you haven't had screws or bolts leftover, had to do back and redo something or replaced a part and it didn't fix the problem you can't call yourself a real DIYer.

HA! So true!