Hi all, I have a problem with my wife's 110 TDi 300.

It's overheating according to the gauge and this is what I've done up to now:

Checked header tank temp - stone cold
Changed thermostat - no change

So I started to take things to bits:

Water pump ok but bought new one;

Checked and replaced all water pipes - found no blockages;

Flushed out radiator - no blockages and very little crap;

Flushed out the main block - no crap came out;

Checked water flow in and out of heater, no flow whatsoever. Is it blocked or is there something inside the heater box that opens and closes the coolant flow?

If the coolant flow in and out of the heater is blocked, could this cause the problem?

Be grateful for any help,

Dave

Wouldn't have thought blocked heater would cause problem.. Especially this time of year.

It sounds like an air lock somewhere in the system.. have you tried bleeding the RAD???

redhand said:

Wouldn't have thought blocked heater would cause problem.. Especially this time of year.

It sounds like an air lock somewhere in the system.. have you tried bleeding the RAD???

Click to expand...

I wondered about an airlock too, but I couldn't find any and did various tests to try and find one.

I still don't understand why no coolant will pass through the heater rad though???

May be the gauge at fault. Caught me out on a 90 300Tdi. Check the earth (ground) on the chassis rail by the battery/seat box. It looks like a little P clip around the earth wire, it's bare wire underneath the P clip but goes loose over time, causing a bad earth to the chassis and bulkhead. This in turn makes the gauge misread.
Worth a look before you say "head gasket"
Like I did:doh:

check the radiator level,and the thermostat level top uo to the top,top the header tank to maximum,then run up with header tank cap off abnd heater on hot,see what its like then,might be worth checking the p gasket while your at it.

Change those **** plastic bungs at the same time, for brass ones.

Ok so this is what I've done:

Run the engine with the header tank cap off, to see if there are any air locks - no change;

Topped-up the rad via it's plug and the thermostat housing (new 'stat) - no change

Flushed out the block via the heater hoses - no change;

Removed the water pump (thought coolant wasn't being pumped) but pump was still good.

Tried to flush out the heater rad - no water will pass????????

Replaced black plastic plugs for brass ones.

The temp gauge appears to work normally, so when the weather allows I plan to see if short-circuiting the heater pipes will cure it - if it does then the fault lies within the heater box - blocked radiator or faulty valve that operates the hot/cold feature.

Thanks to all for your replies

Dave