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Discussion Starter · #1 · (Edited)
First of all great forum, too much useful information. I was planning to keep the car standard, but looking around, it’s definitely not going to stay that way for long!!

Anyway, to my problem, I recently bought an e46 2.0d touring, all seems fine apart from the cabin temperature, when set to 32 it barely gets hot enough to heat the car. Even when left to idle for a good period of time, the temperature gauge does not get past a ¼ and no way near the normal 12 ‘o’clock mark.

Without doing any research, I asked a mechanic to change the thermostat, which he did, however the car is exactly the same.

I haven’t tried bleeding the system (yet) and doubt the mechanic did either, but in my mind an air lock wouldn’t cause the car to under heat.

As well as bleeding the system, is there anything that you guys suggest I look at or consider?
 

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First thing to do is bleed the system then see how you go :thumbsup

How to bleed the cooling system.
1.Jack the front of the vehicle up onto stands as high as possible,
2.Turn the ignition on to Aux 2, Engine OFF, heater on fan setting 1 and temperature fully hot,
3.Remove the rad cap/expansion cap,remove the bleed screw from the radiator and IF you have them the bleed screw(s) from the thermostat housing/top hose, return pipe or EGR thermostat.
4.Fill the radiator/expansion tank up and keep pouring till there are no more air bubbles coming out from the bleeds, using a funnel that fits tight in the expansion tank neck and filling it full of water will help push any troublesome air out, when good you can then install the bleeds and tighten down(don't snap them),ensure the rubber O-rings/seals are still on the screws/on the bleed holes.
5.Suck some water out so it's not full to the brim, start the car up and check coolant shoots out of the small hole on the inside of the expansion tank neck when the revs are held up, if it does then replace the cap and then run the car up and check for heat from the vents when the car is warm, then carry on and check if over heating still persists. You may have to bleed troublesome cars again afterwards.(but very rare).
6.If all is good then check the water level again in the morning when cool.

or

Ignition on, heater set to hot, bleed screw out.
Pull the top hose off the radiator. Pour coolant SLOWLY down the rad hose a litre at a time. When the coolant is building up in the hose, hold it above the level of the rad hose stub and keep adding it. When coolant starts to dribble from the rad, refit the hose. You may find that coolant starts to overflow from the rad cap orifice - if it does, just screw the cap back on. Once you've done that, the engine and radiator are full of coolant - the little air pockets that might be left will come through the bleed
 

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I agree an airlock wouldn't cause an underheat scenario. If the car temp was getting to the 12 o'clock mark and the heaters were remaining cool then it could be an airlock in the heater core but not if the engine temp is remaining low.

Was the stat fitted the right one? Does the temp get to a certain point and remain there? i.e. can you get it to fluctuate up and down depending on driving style? The stat may have a lower temp threshold and be holding the car at a steady, but much lower, temp than it should.

Bring up the temp sensor reading on your cluster and monitor it while driving (but drive safely!) and see if it moves around a lot and where its holding.
 

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Do you have the right amount of antifreeze in the coolant? MAte of mine had a similar problem and it turned out to be static water which had frozen in the radiator.
Switch on the car, turn off the fan and drive a fair distance to get the rad temperature up.
Although more likely to be an airlock, cant rule out ice in these conditions.
 

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Discussion Starter · #6 ·
Right got back to the car today, bled the system just to discount that issue, as expected it made no difference what so ever!

After a 15min drive, I monitored the running temp for another 15 mins, it was fluctuating around 60c, well below the expected 90c.

Checked the part number of the thermostat fitted, it was the same that I would have bought, but without opening the system, I couldn’t really check that the thermostat was the right one.

I saw another thread this week that mentioned it could be the EGR thermostat? Managed to find one today, fitted it, the cars temperature gauge now sits at bang on 12 o clock and the heater is also operating as it should.

Weather permitting, roll on the coilover fitting tomorrow...
 
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