'95 318i Cooling System Preventative Maintenance

[trashmanpenn]

Hey guys, new here, so pardon me if this has been addressed already. I figured it'd be a good idea to replace some cooling system components as my car ages. Which parts are the most crucial to replace? The water pump and thermostat have already been done. Thanks!

[DesktopDave]

I'd replace all the rubber parts while you're in there. BMW coolant is probably best for our cars, but I've had good luck with Zerex G05 coolant and RedLine water wetter.

Mine always ran hot. I'd deleted the mess under the intake and replaced the plastic coolant manifold & o-ring =http://www.realoem.com/bmw/enUS/showparts?id=AJ93-USA-08-1990-E30-BMW-318i&diagId=11_4360(BMW PN 11531714738 & 11531709157, be sure to use the OEM parts). That didn't help much, it kept running hotter so I had to park it. It would overheat pretty badly after about a half-hour of driving.

I figured the cooling system wasn't holding pressure so I replaced all the rubber seals & the pressure cap. Parts 3, 4, 7 & 8 in this diagram. The expansion tank seals looked awful, but I re-used the expansion tank.

I tested it out with this $90 HF pressure tester. The tool seemed overpriced & crappy, but it was worth every penny. At 2bar (30psi) I found coolant leaking from the HVAC drain...so out came the heater core. A new core and new o-rings solved the problem for good. Pumping it up to 2bar with that dumb HF hand pump wasn't fun but it probably saved me a cracked head!