E36 Compact heater is rubbish

[capri_rob]

Saw a mate last night who has recently bought an E36 compact as a daily - just a 316i. Very straight car but its only issue is that the heater is CACK - he does a 40 mile commute each day, the temp gauge sits bang on the middle but he said the heater never gets hot - its warm at best.

Every BMW I've had has had a cracking heater so this doesnt sound right to me.

I'd like to help him out so what order should I check things in ?

[Quaser]

sounds like the thermostat might have been removed, or the water pump not working properly - (i had one once where replacement engine had the water pump had gone - it didnt overheat unless i was in traffic!)

[DanThe]

First thing id check is the heater valve

[harry_p]

Does it actually blow properly?

The heater in mine was rubbish, but the air filters one the heater motor were blocked solid so even on full it made a lot of noise but not much air came out.

Other than that, if it warms up ok and sits in the usual place it's unlikely to be the thermostat, I'd do as Dan says and check the heater valve. Failing that, the matrix may be partially blocked, or the control flaps which control the airflow through the matrix may not be functioning properly.

[DanThe]

Solid pollen filter defo wont help

[pacerpete]

In 97% of instances the problem is related to an airlock / incorrectly bled cooling system.

Due to age , nasty weeping plastic housings , lack of a level sensor and less than bothered council owners , very few M43 engined turdz have fill and forget cooling systems. A PROPERLY bled 'pact heater will be toasty, even at idle. A sure sign of air where there should be coolant is a weak heater at idle that perks up a bit at speed or when you rev the engine.

When bleeding them, be sure to crack off the temp switch / blanking plug on the drivers side top of the rad . Lots of air can be trapped there, even on a car that appears to be bled.

[J6]

our old compact had a heater that just blew warm at best. Flushed the matrix out with a garden hose, lots of rusty water came out.
Did the trick and was toasty hot after that.

[capri_rob]

Thanks for this guys I'll feed this back to him

So Pollen filter, Check heater valve is this similar to the E30 i.e bolted t the heater matrix, a pig to get at but swappable ? and then flush and properly blled through ?

I don't think its a stat issue as he says it gets to temp within a few miles, doesnt overheat and the gauge doesnt move at all from the middle once its warmed up.

He says the directional flaps all work as they should when the controls are moved too - its just the actual heat output thats poo

[Andyboy]

Compacts don't have a regular E36 type heater valve because the heater is a basic air blending type. Start by removing the top heater hose but be VERY careful as plastic pipes love to break. If radweld has been used the matrix will need flushing through. Poor airflow is caused by clogged pollen filters - either fit new ones or just remove and discard.
M43's are very quick and easy to bleed and if the heater is still poor at speed I doubt it will be a bleeding issue.
I would give the cooling system an overhaul, £25 water pump and replace the plastic coolant pipe on the back of the head plus the one on the front of the head.

[Speedtouch]

My Minor's heater wouldn't work at all for ages, until I recently discovered the thermostat should have been fitted in the middle of the sandwich of the (Metro type) thermostat housing, rather than directly to the cylinder head.

Once fitted in the middle of the housing, the heater now works a treat again.

So, could be worth checking that the thermostat is fitted in the correct place, and check that the thermostat works while it's out, by immersing it in a jug of boiling water.

[pacerpete]

My Minor's heater wouldn't work at all for ages, until I recently discovered the thermostat should have been fitted in the middle of the sandwich of the (Metro type) thermostat housing, rather than directly to the cylinder head.

Once fitted in the middle of the housing, the heater now works a treat again.

So, could be worth checking that the thermostat is fitted in the correct place, and check that the thermostat works while it's out, by immersing it in a jug of boiling water.

The M43 thermostat is part of the plastic housing and not replaceable separately. Though I have seen a few that have had the guts beasted out by sad peasants

[capri_rob]

Thanks for the info guys I have copied and pasted the info in an email to my mate and will let you know how we get on

[capri_rob]

I know nothing about 4 pot turds - is the water pump driven by a cambelt ? are the pumps plastic impeller types which can be improved with metal impeller ones ?
Finally is the pump likely to be seized into the block ?

[harry_p]

Same as pretty much any bmw. Pump is at the front run by the accessory belt and has a viscous fan bolted to it.

[bss325i]

M43 is chain driven Rob.

[capri_rob]

Thanks guys

[powelly]

I have a brand new m43 thermostat for sale.

[pacerpete]

Silver X plate 'pact served to pony !