e30s in 100 degree heat

[mikeedler]

drove my e30 with an M20 about 600 miles yesterday in about 100° weather. almost all of it was at over 95 mph, and almost 100 miles of it was on the Nürburgring at full beat down throttle. never went above the 1/2 mark................... until the ride home the top hose decided to split at about 100 mph. then it went to the 3/4 mark. bought some tape at the gas station and topped of the radiator every 80 or so miles the last 200 of the trip.

[5Toes]

My car is weird, almost over cooled. New thermostat and properly bled, all that jazz.

Doesnt approach half mark until I drive it a bit hard. Other wise hovers right around halfway between half and quarter

[jlevie]

When the cooling system is operating correctly a 325i or 325e should see temperatures between 176 and 180F when cruising at 45mph or above in 100F ambients on level ground. That will correspond to the gauge being between the 1st and middle marks (closer to the middle mark). In stop and go traffic with A/C off the temperature may rise to about 185F which corresponds to about the half way point. With A/C on it may reach 190F which is barely above the middle mark.

The gauge isn't all that accurate and the display can vary slightly from car to car and be caused by a bad connection between the gauge and PCB in the cluster or a bad coolant temp sensor. But major deviations are caused by cooling system problems. If the car runs hot only at idle the common causes are:

1) Air in the cooling system
2) Bad fan clutch
3) Bad thermostat
4) Missing fan shroud
5) Inop aux fan if it only happens when A/C is used
6) Bad radiator
7) Gunked up cooling system

If the car runs hot at speed the common causes are:

1) Bad thermostat
2) Bad radiator
3) Gunked up cooling system

The youngest E30 in now 20 years old and probably at 100k or better, which means that it should be on it's third cooling system. The life of the radiator, hoses, expansion tank, cap, thermostat, water pump, and fan clutch is about two timing belts (four years or 80k each). There is no telling what maintenance the car has had in the past or what has been put into the cooling system. If the coolant wasn't changed every other year or if it has been run with plain water there may be a good bit of corrosion in the block, which will cause higher temps.

The smart person that cares about the car will replace every last piece of the cooling system and flush the system with a detergent type flush and follow that with an oxalic acid flush is there is evidence of corrosion in the cooling system. And if the car has working A/C the aux fan has to work properly.

[DaveNorCal]

So I did the newspaper test on the main fan and the fan passed. The auxialliary fan comes on with the AC and did not hesitate when I stuck a folded piece of paper through the grill. So the simpler stuff seems to have been ruled out. It got a new thermostat a bit over a year ago. PRIOR TO THAT IT HAD NO THERMOSTAT which makes me wonder if it has had persistent overheating problems and that was the half-assed repair.
I'd just take it to a shop but don't really know who to trust in Chico and my work situation makes it almost impossible to take the car down to Ryan. Can anyone recommend a shop in Chico?

[DaveNorCal]

To recap, my temp gauge moves past the second mark on hot days, especially sitting at traffic signals. The fan clutch is working as is the auxiliary fan. It's not losing coolant. At operatng temperature, both the upper and lower hoses are about the same temperature, warm but far from too hot to touch, I can grab them comfortably for a few seconds. It got a radiator flush and new thermostat in march 2011 and has probably not been driven over 10K since then. When the system was flushed and the thermostat replaced the shop notes say "Radiator has some build up." The thermostat part number was 11531466174.

[DaveNorCal]

Any further thoughts? Spring is approaching and I'm going to have to do something before summer. I'm thinking it has a gunked up radiator. Somewhere I read that there is an e36 m3 radiator that is a bolt in and has much higher capacity. Would that be something to look into. I may just need to take it down to RyanG in Auburn as I've had further disappointing results form the "reputable shop" I referred to earlier.

[jlevie]

Any further thoughts? Spring is approaching and I'm going to have to do something before summer. I'm thinking it has a gunked up radiator. Somewhere I read that there is an e36 m3 radiator that is a bolt in and has much higher capacity. Would that be something to look into. I may just need to take it down to RyanG in Auburn as I've had further disappointing results form the "reputable shop" I referred to earlier.

On this car you can use an E36 radiator, but the OE radiator will be fine if there aren't other problems. Before you change the radiator do a system flush (procedure below). You should also, to avoid a future failure, replace the expansion tank, cap, and all hoses. Even though the thermostat should be good, I'd replace it with a OE part also.


1) Get the front of the car 1-2' in the air on jack-stands.

2) Drain the coolant, remove the thermostat, and set the heater controls for
full hot. O-ring sealed thermostats require you to make up a temporary
gasket, which can be made out of pasteboard.

3) Add flush compound and fill with plain water. Then run the engine at normal
temperature as specified by the flush manufacturer (usually about 15
minutes at operating temperature). In cooler weather it may be necessary to
block off some of the air into the radiator to decrease the warmup time.

4) Allow the engine to cool until you can place your hand on the cylinder head
w/o discomfort. Drain the system and refill with plain water.

5) Run the engine for 10-15 minutes or until temp is close to normal.

6) Repeat (4) and (5) until the water drained from the system is clear and
free of debris.

7) Fill with coolant. It is best to dilute aiitfreeze with distilled water.
Tap water contains disolved oxygen and may contain minerals. Either of
which will reduce the lifetime of the coolant.

Notes:

You don't absolutely need to remove the thermostat, but doing so will allow
continuous flow through the radiator and will also make draining & filling
faster and easier.

Always allow the engine to cool to the point that you can hold your hand on
the cylinder head without discomfort. That will prevent scalds from hot
coolant and prevent thermally shocking the head when you dump the coolant.

Filling the system with hot water makes the process go faster and keeps from
having to run the engine a lot in a cold condition (rich mixture).

A rusty cooling system needs an oxalic acid flush. Kits for that (containing
oxalic acid and soda for neutralizing the acid) used to be available, but
arent now. 8oz of oxalic acid and 4oz of soda will treat a 1-1/2 to 2 gallon
cooling system. The procedure is like the above with an extra step 4 where the
soda is added before the series of fill/drains are done. Since oxalic acid
attacks aluminum (which is why you don't find those kits anymore), only use
that on a badly rusted cooling system and replace the radiator and heater core
after the flush is done.

[DaveNorCal]

Thanks Jim.