DIY Coolant System Pressure Test

[DRTE30]

I have been chasing a slight coolant leak since I took ownership of my 318is about three years ago.  Ever since I did the "Mess Under the Intake" clean up, I have had this leak.  I am generally losing about 1/3 cup every two weeks, measuring from the cold water line on the expansion tank.  Though, it is not too terribly much in coolant loss, there shouldn't be any loss at all.  What's worse is that I cannot visually see this as the engine is running and up to operating temperature.  This has me thinking that it is slowly boiling off and cannot be visually seen as a drip or condensation somewhere- or worst case and the head gasket has gone bad in a non critical spot.

Finally having the time to chase cooling/heating and AC issues, I got the motivation to call up a local auto parts store to rent a coolant system pressure tester.  A quick side note, if you've spent any length of time living in Hawaii, you will be familiar with how brain dead the general population is.  Before I drove down to rent this tool, I had three different employees verify that they had a tester for a BMW on hand.  Ok, great...I'll be right there.  I picked up the tool, and drove home to find that it doesn't fit and in tiny little print it states that the adapter is for GM cars only.  So I call the guy up and tell him, and he replys "Sorry brah, no can. We no have any ting for BMW. Nevah have".  Well...I guess that's life.

The next option was ordering a kit through Harbor Freight.  It's originally $120 and some change, but currently on sale for $74.  Though, the reviews for the kit are mix match and everyone complains about how brittle the adapters are.  Also, I don't need a ton of different adapters.  Lastly, this is a tool that will rarely be used, so the cost outweighs the means.  I finally settled on going to the junk yard where I picked up a radiator cap.  I brought it home, drilled a hole straight through the center of it and inserted a schrader valve from an old beach cruiser bike tube, then epoxied around the valve and feathered it out.  It took all of five minutes to complete and I will give it a go over the next few days.  I have included pictures of the final product.

Items needed:
Radiator Cap
Schrader or presta valve from bike tube
Razor blade or utility scissors
Drill with various bits
Chanel locks, vice or vice grips
flat end screw driver
silicon epoxy or 2-stage epoxy
bicycle pump w/gauge
air pressure gauge (if not built into pump)
iced coffee (in my case) or beer

1) Begin by securely fastening the radiator cap such that the center mechanism with the two o-rings does not spin freely.
2) Use a small diameter drill bit as a pilot hole, and center the drill bit on the cap and drill straight through until it pokes out the other end*.
3) Continue stepping up in drill bit size until you are satisfied with the hole needed on the top of the radiator cap to properly insert and secure your bike valve.
4) Rough up the surface of the radiator cap with sand paper to give your epoxy something better to adhere to.  Clean and let dry.
4) Prepare the bicycle tube valve by cutting it off of the tube BUT leave material around the valve.
5) Trim the rubber around the valve such that you have a circular flap/gusset.
6) Take your valve and your flat head screw driver and push your rubber gusset into the hole you drilled at the top of the radiator cap until it is completely in place.
All of the rubber gusset should be pushed inside the hole, the valve should be poking straight out, and the two o-ring center should spin freely.
9) Next prepare your epoxy and apply as you see fit. Be mindful to take something flat and work it into and around the base of your bicycle valve to mitigate any air leaks. Wiggle the valve around as well to work in the epoxy as best as possible.
10) Follow the instructions per your epoxy of choice and let fully cure.
11) Admire your handy work, open your beer and boast to your wife/girlfriend about your cool contraption and all the rad things you can do with it.
12) Once cured and you're ready, install the cap, connect pump and pressurize the system to the OEM specification for your system**.
13) Look for leaks. It may be obvious; it may not. It may involve removing your lower dash to access the interior heater core and plumbing or it may involve getting under your car to look for drips.  Worst case if you have exhausted all coolant connections, you pull spark plugs and look for coolant seeping into the cylinder(s). Oh Duh moment: Everything could be fine in your system and you are certain of this yet don't know where else to look: the radiator cap you are using may no longer be effective and needs to be replaced.

*You may not need to drill completely through the center of this piece (see last picture) as this mechanism isn't entirely air tight. I did it to allow air to pump more easily into the system.
**Do this incrementally and check your pressure. It is in your best interest to not over-pressurize the system.  Use a digital gauge like I have, if needed.

[bigskyis]

Did you find your leak? Not to change the subject, but is there not some sort of dye you can put in the coolant, run the engine for a while to circulate the dye and then inspect with a black light to find the leak? Pretty sure there is. I am thinking that would be the path of least resistance.

[bmwman91]

You should not be losing any coolant to evaporation, unless you have a cracked head and it is going out the exhaust...which would be arguably worse than a slight leak!

I too have had a similar leak, and I think that I finally found it last night. Similarly, I did the mess under the intake mod and replaced all of my hoses + plastic water pipe at the same time. I FINALLY checked closely where the heater core hoses connect to the firewall and noticed a small green puddle on the rubber boot thingy around the metal water pipes that go to the heater core. The two hoses do not seem to be cracked or anything, so maybe I got the hose clamp on crooked or something. Anyway, I took the hose clamps off and re-tightened them, making sure that they were straight. The lower hose clamp is a real pain in the ass, so maybe I just failed to tighten it fully last time. Anyway, check around there. I think that it is easy to overlook that area.

Thanks for the write-up on how to pressure test the system cheaply. Hopefully I won't need to, but at least I can now!

[DesktopDave]

11) Admire your handy work, open your beer and boast to your wife/girlfriend about your cool contraption and all the rad things you can do with it.

LOL!

That's a good write-up.  I just bought a new Mity-Vac pressure test kit for my bikes.  It'll do most domestic and Asian cars, but not BMW.  Happily they do offer various adapters.  You're likely ahead on the cost though.

[DRTE30]

Update:

I finally had time to test the system and found that there were a few leaks around the bypass valve and where the heater core pipes connect to the heater core.  After that, new hoses were ordered and I set aside some time yesterday to install hose #'s 4, 22, and 23 as well as a new thermostat and a couple new vacuum hoses.
http://realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=11_1272&hg=11&fg=35

I also replaced sensors: 6 & 8
http://realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=11_4373&hg=11&fg=15

Currently, my car is on an inclined driveway with the nose end being up the incline as well as being on ramps to increase the angle for bleeding the coolant system.  I took the advice of others online and pre-filled hose #1. Also, before starting the engine, I turned the key to 'power on' and turned the heat dial to activate the heater valve and open it to allow coolant to flow into the heater core.  After that, I started the engine and began the slow process of bleeding the system of air and adding coolant as needed.

While everything seems to be fine, there is still one inherent issue: the car is still not producing any heat out of the vents! Part of the purpose of tackling this system was to get my heat back.  I am still having no luck and to make observations easier to follow, I have compiled the following cliff notes to help diagnose my no-heat issue:
*Mess under the intake following t1tj's write-up.
*Removed factory recalled heater core bypass valve located behind the head and in front of the firewall (it was leaking).
*Removed original non-working heater core valve. Replaced with used, working unit.
*Removed original heater core, flushed, checked for leaks and reinstalled.
*New coolant hose #4 from lower driver side rad to black plastic pipe side-bung (which is connected to the engine block).
*New coolant hose #22 from UPPER heater core pipe to black plastic pipe on engine block.
*New coolant hose #23 from rear of head to LOWER heater core pipe.
*New thermostat, o-ring, and housing gasket.
*The water pump was replaced with a new OEM unit about a year ago.
*I have verified 12v going to the connector at the heater valve when appropriate and in regard to the climate control knob.
*Radiator cap was replaced about three years ago, but I tested it for leaks and is still in proper working order.

Problems/Thoughts:
*No heat.  I suspect hose #'s 22 & 23 are hooked up to the wrong pipes for the heater core.  Can someone with first-hand knowledge please verify the routing? The internet is so full of misinformation.  I've read "follow the diagram on realoem" and I've read "that diagram is B/S. Switch the hoses".
*I can verify that the heater core is hot, because I have not put my lower dash back together I can physically touch each part.
* The upper heater core pipe on both sides of the heater core valve are hot.  The lower heater core pipe is luke warm at best.
*On the engine side of the heater core pipes, the upper one is hot, the lower one is luke warm.
*The three hoses from the radiator to the engine are all equally hot.
*Hoses 22 & 23 I pretty much strangled during the bleeding process to mitigate air pockets.  My thought is that these hoses would probably be in better shape if they were back filled at the fire wall connections to minimize the possibility of air getting trapped.  Those two respective hoses have so many bends, that it wouldn't surprise me if air was in fact trapped.
*The thermostat is functioning properly, and the electric fan I installed operates as usual.

Any thoughts or ideas would be rad. Thanks in advance for your help!

[Slowered318]

Did you delete the heater core bypass valve?

I got tripped up by realOEM too, but now I know, the longer hose goes from the plastic heat pipe to the upper heater core connection on the firewall.

I've never done all these fancy coolant bleeding processes. I just flush generously with a garden hose, use a shop vac to blow/suck the tap water out of the system. Then fill it up with 50/50 BMW blue and distilled water, bleed the radiator with it running then take it for a drive with my coolant jug in the trunk to top up if needed.

[DRTE30]

Yes, the heater core bypass valve was removed.  That thing was leaking at every fitting.  Rather than replace it, I thought it was best to simply remove, and reduce the amount of probable future leaks- after all, removing it gets rid of six hose clamps.  Also, I am not sure if others' cars have this, but my E30 has an aluminum splash shield that bolts to the left side of the heater core. It's about 25cm long by 16cm high.

Did you mean that you fill with a garden hose, and use your shop vac to suck the AIR out of the system?  Lastly, thank you for the clarification on the hose orientation.

[DesktopDave]

I'd be very suspicious of that heater core.  Seems like it's plugged.  You flushed it, did it flow really well?  I'd be tempted to drain the system again, then put a hose on one of the connections and see how well it flows.  If not there, perhaps the feed or return hoses have a kink or blockage?

[monty23psk]

I haven't read the full thread but if you heater valve is bad, it will stay closed by default and no hot coolant will run through heater core. You might be able to hear it click/thump if you have car switch on II and you move the temp knob from cold to heat. On the e28, they are stuck open if they do not work, so when you only get heat in the car with it off, you know the heater valve failed.

[DRTE30]

Oh mein Gott, hat mein Auto Hitze! Es ist so warm, dass ich wahrscheinlich eine Tute Popcorn aus den mittleren Beluftungsdusen! Vielen Danke fur jedermanns Vorschlage!

[monty23psk]

So what was it?

[DRTE30]

Well, it was a combination of everything that I did above, I would say.  I think the biggest things that made the largest difference were:
*Removing the bypass valve located above the transmission and sandwiched between the firewall and head. This thing was leaking at the connections, and I was unsure if the valve it self was also malfunctioning.
*Replacing the heater valve attached to the heater core.
*Installing hose #22 and #23 to the original orientation per realoem.
*Installing a new thermostat.
*Bleeding the system multiple times on an incline.
*Taking the climate control knob and twisting it rather hard to make it make a "thwomp" noise to bust loose any dust/dirt and to ensure that I can hear the flap changing from cool to warm.
*Flushing the heater core with a high pressure hose until the water ran clear and of any foreign particulate.

Last night as I drove, with the hoses #22 and #23 reversed at the firewall, my car still did produce heat. I was surprised.  However, it wasn't until reversing those two hoses (following the realoem diagram and to the normal configuration) as suggested by Slowered that made a significant difference in that the heat output is substantially higher.  So the hose orientation absolutely does matter.  Some online say not to worry, no big deal, but there is a difference and I now have first hand knowledge of this.  Du habst eine frage? Go for it and I'll answer as clearly as I can.

[Slowered318]

Hey, glad that worked out finally.

I'm not sure what the climate is like in your area, but here up north taking off the clutch fan in favour of an electric seems to keep the coolant nice and hot. I hardly ever hear the fan come on, only in the summer stuck at a traffic light. If your somewhere south or at the track I wouldn't advise this, you may have problems with excess heat build up in the engine bay.