Had some heating problems recently.. some advice given to me

[BigKriss]

from Zygoteer aka Tony from the UK. His answer to me via e-mail was so damm comphrensive I had to post it on here. My problem was that I tried to remove the heater valves above the heater pump and somehow I made a small crack around the bottom of the pump. I removed it and inspected it, it looked fine. I put it in the car again, and the same problem kept on coming up (overheating). I don't know how, probably me moving it around too much. Currently I'm running without one, I just blocked up the cylinder block coolant hose and joined the two hoses together that goes to the (air con / heater) - i think. From the small crack i was losing coolant, and the car was overheating. Bleeding the cooling system did very little.

Here's what he said verbatim.

You will very probably know most of this, so ignore those bits - sorry, but included for completeness … hope this helps you get over your problem.

The overheating WILL be due to a fluid loss somewhere, or a fault causing fluid to be boiled off/vented.
- remember in a so-called 'closed' system, a loss of fluid will always be replaced with air, so your 'bleeding' approach is the right way to go initially, as simply air is not a good 'coolant' - remember to do this with the heater valves open (maybe a valve is sticking and not letting the water/air through?).

... by the way, while trying to find the root cause of this, I would just use water and only use the BMW coolant when the real problem is fixed.

If the bleeding is not successful, then the following is what springs to mind and may help you (remember it is not forced to be only one fault, it can be a combination, as one fault often provokes another before it becomes apparent enough to make you fix it ! ).

1. Losses
either :
from 'plumbing' (hoses/pipes) in engine bay or inside the car.
or :
from the heater core itself.
or :
from the engine (pump gasket or head gasket usually, a 'porous' block doesn't bear thinking about and would have shown up way before this point in its life).

2. Faults
either :
a restricted flow, due to a blockage somewhere (not as common as some would say, but if so, is most likely to be in the radiator or heater core, mostly because someone has used contaminated coolant or one of those 'leak repair' fluids you see for sale in motor stores).

or :
bad pump, causing low flow (or if the plastic vanes have disintegrated then NO flow!).
or :
bad thermostat, causing a restricted flow.

To summarize the fixes for these ...
a) ensure integrity of all connections, but be careful not to over-tighten hoses on plastic piping/radiator/header tank etc., as plastics fracture all too easily when old and cold.

b) check for water leaks on outside of engine (maybe head gasket, but that would be a rare failure mode) and in particular around water pump (DON’T remove pump unless you have a new gasket already).

c) check your foot-well under-carpets to see effects of a leak inside the car from heater core/connections - replacing the core is non-trivial though

d) check engine oil for signs of water in there (common symptom of head gasket failure = leak from water jacket to oil way).

e) check the exhaust for white 'smoke' which is actually steam (another common symptom of head gasket failure = leak from water jacket to cylinder) - be aware that significant water/steam in the exhaust can kill your lambda (O2) sensor.

f) the only way to really check the thermostat is to remove it ( - this is not as drastic as you might think as the gasket is an O-ring which is not usually damaged, so can in fact be re-used, but check it carefully by first cleaning it using a little grease smeared on it to soften the crud then wiping it so it comes off without damage - also check for surface nicks/cracks that will be a leak path, it must be a smooth continuous surface) .

A bad thermostat can be due to :
(i) wrong operating temperature (the temperature response DOES change as the pellet ages).
... despite what was implied on the bimmer forum, it is a perfectly ok to heat it in water to see the opening happen at the right temperature, heat the water slowly when above 75 deg C so you remain in control - simply do not over 'boil' it.

Check the temperature rating as suitable for your country/climate, it should start to open and be fully open over about a 5 deg C range - if it takes a bigger range, the odds are it is a problem and needs replacement.

(ii) non-optimum/incorrect fitting (I've variously seen reverse fitting [as found on my Ferrari!], O-ring gasket put on wrong side, bad orientation - check your Bentley book)

... before fitting new or old units, drill a 1/16th" (1.5mm) hole in the dimple on the flange, to allow easy bleeding (this really does help on the M30) - such a bypass won't affect your cooling system performance as the flow rate is minimal from such a small hole, but it does allow gases to rapidly escape towards the bleed point.

The thermostat fitting orientation should be such the dimple/hole is at the uppermost point (gases such as air are lower density than water, so will accumulate at the highest point).

It is important to thoroughly clean the O-ring groove in the housing so that the surface is smooth, use a little grease on the O-ring when fitting.

The worst scenario is the head gasket, but on the 535 this is not actually complicated, just very tedious as there is a lot of stuff to be removed - most difficult bit is remembering where all the little hoses go and the cable routing - oh and also the exhaust manifold (headers), as there is very little clearance/access while the system is still on a RHD car because of steering box - but it can be done (don't know if your car is LHD or RHD).

… its always a bummer when your bimmer doesn't work correctly ! ... but keep smiling

On a seperate note, can you guys give me the part number for the water pump and heater valves (one unit). I've "almost found" it, I just can't see it anywhere.

http://www.realoem.com/bmw/partgrp.d...id=47382&hg=64

[Paul in NZ]

is it isnt it ??

[BigKriss]

thanks Paul it is there, item 1 is the pump and item 15 is the valves. thanks mate

[uscharalph]

I'm not sure whether the heater core was the instigator of my previous problems or if my previous problems burst my heater core. Probably the first.