bmw 2002

Sealing the Cooling System

Nov 28, 2008

     I've had nothing but problems with Webby's cooling system.  For the longest time, the cooling system wasn't even a concern of mine.  But that was because it was empty.  Empty systems don't leak.

     Well, now that the car actually runs, keeping the engine from overheating is a big concern.  Yet, each time I filled the cooling system, it leaked.  Never from more than one place at a time, though.  Every time I plugged one leak, another seemed to pop up.  Some were worse than others, but all of them were annoying and couldn't be ignored.

The first order of business is removing the radiator.  It's been eaten by the fan and has always looked bad.  I had a re-cored radiator on the shelf, so let's swap them out.  I emptied most of the coolant by pulling the lower radiator hose, letting it pour into a catch pan through a funnel.


On the right, Webby's original radiator.  On the left, a re-cored radiator that's been in storage for many, many years.  The re-core hasn't been destroyed by the engine's fan, so I figured it would hold water better than Webby's radiator.

radiator removed

But I was wrong.  It turns out that the re-cored radiator leaked terribly.  After I installed it in the car and filled the system with fluid, it seeped out from numerous places between the radiator fins.  So, I took both radiators to a small, local radiator shop and had them both leak-tested.  Well, the ratty looking one that's been in the car for decades and has been torn apart by the fan holds water just fine.  The re-core is like Swiss cheese.

Another leak to plug.  With an intact radiator back in, I filled the system with coolant, but no luck.  I had replaced the intake manifold a long time age.  The manifold has a coolant fitting on the bottom of it, and coolant kept spilling from between the manifold and the fitting.  Here, I've pulled off the fitting.

intake coolant fitting removed

Scraping off the old gasket that wasn't working.

intake coolant fitting dirty intake coolant fitting clean

Here's a new gasket, purchased from the local dealership.  It was much easier to install than custom-cutting some gasket paper.  It turns out that this didn't work either.  The bolts holding the fitting to the manifold were a tad too long.  They'd feel tight, but were bottoming-out in the manifold.  Some shorter bolts fixed that leak.

intake coolant fitting new gasket

Even with all this fixed, the engine still seeped coolant from somewhere up front, just enough to hit the fan and spray all over the place.  I figured that the water pump's gasket was leaking, or perhaps one of the old rubber hoses.  $75 got me a new water pump, thermostat, and a whole new set of hoses, so I ordered them all up from Autohaus Arizona and decided to swap them all out at once.

Bad water pumps are common on '02s, but this is ridiculous.  Removing the water pump revealed that its insides were completely encrusted with deposits, and, worse, gummed-up with Silicone sealant.  Someone in the past used a lot of sealant to either fix a leak or seal the water pump's gasket.  Either way, they used way too much, and this water pump probably wasn't pumping very much coolant through the system.  That circular piece is an impeller that spins and moves the coolant, but it's largely surrounded in gunk.

old water pump

Looking through the grille reveals the alternator in the top-right and the water pump's mount on the left.  It's pretty gross behind that pump.

water pump housing

On the right is the engine's pully.  It spins with the engine and drives the fan, water pump, and alternator via the fan belt.  I've cleaned the water pump's mount of crust, Silicone, and old gasket material to make a clean surface for the new water pump gasket.

water pump housing dirty water pump housing clean

Here's the new water pump, with new gasket, bolted to the front of the engine.  The fan mounts to it on the black circular piece on the right.

new water pump

Left:  the fan has been put back on and the fan belt re-installed.  Right:  with a new thermostat, hoses, and hose clamps all around, the radiator is dropped back into place.  The system is now completely back together.

new fan belt new coolant hoses

And it all appears to hold water, for now.  At least it holds water when you bother to tighten all of the hose clamps.  For a fairly low-pressure system, it sure does spring leaks pretty easily.

Here's a fun game:  count how many times I had to fix a leak.  Each time I say "it didn't work" or give some little piece of wisdom, that's a leak that I had to figure out and fix.  You'll have more fun counting than I had fixing.

Maybe my next project car will be air-cooled.  VW?  Porsche?  Corvair?