Coolant woes..

[SlickGT1]

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.

[sunny5280]

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.

[SlickGT1]

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.

[crystalworks]

Originally Posted by SlickGT1

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.

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

[SlickGT1]

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.

[jdstrickland]

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.

[IX5DOU]

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.

[Rockit]

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.

[IX5DOU]

Sorry to offend. Just trying to help.

[StephenVA]

Originally Posted by Rockit

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.

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.