E36 328i Overheating - Head gasket? - Update!

[roo 41]

While driving on the motorway last weekend I could smell hot/buring coolant so I looked at temp gauge and it was pretty high. Pulled over, turned the car off and let it cool a bit. Opened rad cap, topped it up then tried starting it again. It quickly got up past normal operating temp so I turned it off and called a tow truck.

Water is crystal clear and bright green, oil is clean too. No gunge under the oil filler cap either. I know water pumps go on these motors pretty often on, anything else?

I would love to think it is a coolant leak or something like blown water pump but I am leaning towards HG because the back of the car was covered in little droplets of greasy clear water. They never really dried either. Could be a coincidence and maybe some truck sprayed the car or something but seeing that tells me water must be getting into the exhaust system.

What should I be looking for diagnose the problem? Going to pull plugs and check for water/condensation and check thermostat & water pump. Leak down test? TK test? Pressure test the cooling system?

Really keen to get this sorted as the car is super tidy and only done 103kms. Thanks!

Edited April 10, 2013 by roo

[euroriffic 603]

I'd say the water pump would of failed at around those kms and guessing it's never been done before. The t.stat usually gets abit sticky in old age but generally wont shut properly so takes a while to heat up like my 328 I just not long did and the waterpumps have been known to shear the plastic impeller off so it doesn't spin. Would still pay to check h.g to see if it's alight.

[rowans17 19]

At that low kms its very unlikely (but not impossible) that its the HG. Waterpumps on those engines are a joke - basically a service item. Drain the cooling system and take a look if your brave, flushing the coolant could also help diagnose this issue. If your coolant was just low causing you to overheat you may just need a new thermostat.

[thorburn 120]

Diagnose it properly with sniffer test and or leakdown test. If that all passes check the individual parts in the cooling system.

Overheating leads to head sealing issues. Doesn't matter what k's

[roo 41]

Update:

I spent some time on the car tonight. Car idled for about 20-25 minutes, got up to operating temp and stayed there. Rad cap was off the whole time.

- No water being pushed out, bar the odd bubble (water slowly lapped over the edge every now and then but this is to be expected as water pump circulates right?)

- No change in water height when revving

- No water coming out of exhaust, held a piece of paper over it while revving

- Temp didn't rise past half (normal operating)

The bottom rad hose never get hot, and the water level never dropped when it got to operating temp. So this tells me thermostat is toast? It was running for almost half an hour, more than enough time for thermo to open.

Also - heater won't blow warm air. Set to 32deg and AC on full it blows cold air. This is strange. Even if thermo was f**ked it should still blow hot air right? Maybe blockage in the heater core? Could this cause the over heating by not letting the water circulate properly?

Pulling thermo and water pump off tomorrow to inspect. If those are fine then might look at heater core/pressure test cooling system. But I'm leaning away from any leaks now as the water level never dropped and that bottom rad hose should't have stayed cold.

Thoughts?

[euroriffic 603]

I'm assuming the heater used to work before hand and a dodgey thermostat wouldn't affect it but a blockage or an air block will. Radiator could also be blocked causing the overheat. Otherwise it could be the valve not operating as to why theres no heat. Also The m50s can be a pig to bleed if not done right. If you can rule out you havn't damaged the head from it overheating I would be replacing the t.stat and pump as it's a cheap, easy and good mantainece even if its not at fault, more piece of mind knowing it's done and won't need done for another 80-100k. And get a new plastic or alloy (recommend!) replacement thermostat housing as you WILL damage it changing the t.stat. Refill using correct method-slowly and with the front jacked right up to allow air to travel up and out with heater on. If properly bled and heater valve is working it should blow warm,'if not you have a blocked heater core or still air lock so will need properly flushed and bled by the pros.

Failing that just take it to someone who knows what they're doing. Can be alot easier in the long run

[roo 41]

No idea if the heater used to work as I have only had the car in summer.

Any tips to hold the fan in place while you undo it?

[euroriffic 603]

Don't need to hold it, just kghit the 32mm spanner with a hammer afew times and remember its left hand thread

[roo 41]

Have done that, doesn't budge. BMW have a tool to hold the water pump bolts.

[euroriffic 603]

Get a bigger hammer haha. The one on my m3 took an to get off

[roo 41]

I don't think either of these are suppose to look like this! Replaced them both with genuine ones, bled the system and took it for a very spirited 20 min drive. Bottom rad hose got hot, heater pumped hot air too. Temp never went above half. Hopefully she's fixed! Real test will be sitting in traffic tomorrow for 40 minutes. Now I just hope no damage was done do the head when it got hot.

[euroriffic 603]

Good to hear you got it sorted. That pump looks like it's seen better days, does the impeller spin on the shaft?