Heater Core/Valve Leak

[Nürburgring]

I believe you could do a heater core flush and you'd find out if you have a leak or not...

Buy a kit for $4 from autozone and watch the ChrisFix youtube video on how to do the flush...the only difference will be that the water you run during the flush will be cold garden hose water instead of near boiling coolant fluid. Under extra pressure, you may have a leak whereas with cold water and low pressure you may not show it.

http://www.bing.com/videos/search?q=chris+fix+heater+flush&view=detail&mid=E2A575FF3BFACF223B7FE2A575FF3BFACF223B7F&FORM=VIRE1

[Pennyw1se]

The previous owner bypassed the tubes at the firewall and I am assuming this was done because of a valve or core failure. This hasn't caused any overheating issues so I have left it alone.
What is the best/easiest way to test for a leak without reconnecting hoses? Could I run water through both pipes at the firewall with the ignition off and look for a leak since the valve is open at this point, or does there need to be pressure in order for the leak to appear? Is the heater core essentially a small radiator that can be removed then checked for leaks by filling with water and checking for leaks somewhere?
I have a spare parts car that I may be able to swap parts with but I'd like to bench test before I start swapping so I don't waste my time on useless parts.

[Ceeker]

visual test for leak:

I have encountered this problem a good number of times. In my history of these cars rarely do the heater cores give problems unless the model questioned did NOT get the SIB from bmw when they had exploding cores. Once the SIB took effect core issues were rare.

look for sweat around the heater tap - most likely the issue with your leak. if you end up changing that, change the 3 o-rings as well.

[OttoBob]

Good idea...I've had the console out before, so that is easy. Right now my carpet is unaffected. Thanks.

[KillaCams]

I would at least pull the center console and take a look at the connections and look for any leaks, it may be in the beginning stages of leaking. Nip it at the bud now before your carpet becomes soaked in coolant, its a PITA to clean.

Edit: or before it gets colder and you have no heat

[StereoInstaller1]

If your feet suddenly get really hot and all your windows fog completely, instantly, you will know...right?

Ask me how I know!

[OttoBob]

This is all great info...but I may not have a problem after all. Since I cleaned my rubber floor mat really well, I have not seen any coolant/fluid reappear. I am not sure what to make of it. I may have gotten some oil or coolant on my boots that transferred to the mat, but general I have only been tromping around in the snow, so I expect water on a regular basis and then dry mats after the water has evaporated. When the mat did not dry the other day, I checked it with my finger, and it was a slippery/oily fluid, and a fair amount of it, so I became concerned thus the original post. Thanks for all the input. Now I am ready with the know how to do the job if needed.

[KillaCams]

Thanks again for the information, good to know.

OP: did you get this issue sorted yet?

[jlevie]

The flow for the heater comes out of the back of the block, through the heater and then to the intake side of the pump. That allows the heater to work whether the thermostat is open (and the radiator hot) or not. In really cold weather the radiator won't ever reach engine temperature, so this provides heat in those conditions (or soon after starting in milder weather). When heat isn't being used the heater valve will be closed and that flow is blocked.

If you loop the hoses you cause flow from the back of the head to the pump intake all the time. That flow doesn't go through the raidiator and can result in higher than normal engine temperatures (or even overheating).

[KillaCams]

Never loop the heater hoses to bypass a leaking hater core. That will short circuit part to the coolant flow that should be going through the radiator. If you have to bypass the core, plug each hose.

Good to know, although i ran my car looped for a few months and it was fine Would you mind explaining more? The hose off the back of the head runs into the heater core, then from the heater core it runs to the front of the cooling system. It seems to me that plugging both ends would reduce coolant flow, not questioning your knowledge but trying to further understand the reason behind it.

Thanks

[komarkjevin]

when I bought my 96 740 that i had many leaks.the place has the water pump, said / watervalve was bad and it costs only 700 bmw.sure that is exactly what was leaking, but I told him I have to lose to bring him to see what appeared to leaking.well escapes the bottom of the water pump.

[jlevie]

If you need to drive the car you can loop the hoses under the hood to bypass the heater core, at least until you're able to pull it apart and replace what's leaking.

Never loop the heater hoses to bypass a leaking heater core. That will short circuit part to the coolant flow that should be going through the radiator. If you have to bypass the core, plug each hose.

[KillaCams]

Yea i know what you mean, but at least so you can drive the car to get parts, to work etc. Late model is easy, pull out your center console and you should be able to figure out where it's leaking. Mine was leaking at the heater control valve so i just changed that and replaced the o rings since i didn't have enough money to do the core at the same time.

This write up helped me when i did mine:

http://www.r3vlimited.com/board/showthread.php?t=98782&highlight=replacing+heater+core

[OttoBob]

Thanks for the input...No heat is not much of an option since it is late December in snow country. The Bentley manual gives me the basic steps, but how difficult is it to get the heater core in and out once I've got the interior apart?

[KillaCams]

If you need to drive the car you can loop the hoses under the hood to bypass the heater core, at least until you're able to pull it apart and replace what's leaking.