First Posting: Overheating

[HawaiiTi]

Hey, gang, first posting...my wife's 1996 Montreal Blue Cali (93K miles) overheated.

Privateer shop installed 'stat. Ran fine for a day, overheated, cracked the gooseneck. Told the techs I thought it might be insufficient bleeding (thanks, 318 ti forum), bled it, replaced gooseneck, ran fine, overheated a day later.

Pulled, visually/physically inspected water pump - it's fine. Proactively replaced the fan assembly. Ran fine for a day...overheated.

I'm back to 'it's a bleeding thing'. Told them to raise the nose, put the heat on high, cycle it a couple of times...all the stuff recommended elsewhere in the forum. Any thoughts appreciated. The good news - this hassle brought me to 318ti.org!

[BMWDRIFTER]

is it still overhaeting?

[HawaiiTi]

Thanks for asking. What a saga...

Where we are: the deduction is that the relay in the fan assembly was the original culprit (intermittent cutting out of fan), which caused the initial overheat, which toasted the stat.

Problem initially misdiagnosed as bad stat, stat replaced, fan cut out again, overheating again, blowing gooseneck. Fan assembly replaced, overheated again.

This time caused, it is surmised, by a previously unseen hairline crack in radiator (said crack resulting from previous overheat) sucking air causing third overheat.

So, new radiator is the last step in this process, God willing (stat, radiator, fan assembly, water pump). The good news? Replacement of the (still good) plastic-impeller water pump with a new metal impeller one (thanks, forum). And I replaced a lot of strand-you parts at what is probably the right time (93K miles).

The other good news. My techs are being very fair/generous, as the initial misdiagnosis has led to a raft of otherwise avoidable problems.

p.s. Plastic radiators...what a concept.

[motorsport]

you havn't taken the thermostat into consideration? that is a pretty common cause of overheating. if the radiator doesn't fix it just buy a new thermostat. you can install it yourself real easy. just follow the inlet hose from the radiator to the top of the motor. pull it off and the thermostat is right there.

[HawaiiTi]

See first line first post...the thermostat was the first thing replaced, but, after long sleuthing, we determined that original, good 'stat had been cooked by an overeheat created by the intermittently-cutting-out-fan. Which also produced an unseen hairline crack in the radiator which caused the NEXT overheat by allowing air sucking through the crack when the engine was at operating temperature. Thanks for replying to my thread.

[BMWDRIFTER]

glad it is fixed. As mechanics we love BMW plastic, it gives us plenty of work. Buy a 99 or newer 3 series and the t-stat is also plactic. How did that work out.....Not to good ( repeat sentence #2 ).