Outer Limits 4x4 Board

The heater unit in MQ leaks coolant when you put the temperature control on heat. i noticed this when i got the cooling system flushed the other day the passenger side floor was covered in coolant. I have taken the whole dash off and have nearly gotten the whole unit out.

Has anyone else has this happen to their MQ, if so what is the main parts that usually leak eg (heater core or something) and is it hard to replace.

i have another MQ which i think the heater unit is ok but i just dont want to spend a few other getting that one out.

so if anyone can give me some pointers on this, coz it's proving to be a very time consuming job.

thanks in advance

Sacha

I have gone through this before also.
I pulled out my heater unit to test it and it doesnt leak.

You will find that the problem lies in the metal pipe going through the firewall where the heater hoses attach to either side.
If the coolent is only coming out on the passenger floor and not in the engine bay, u will have to get ur hands in behind the heater unit and push the hoses on further and put new hose clamps on and make sure there tight.

Hope this Helps.

Screwy

There is a switch that turns the water on & off to the actuall heater core.
Its located between the back if the heater box and the firewall and NO you cant get at it in an easy way sorry !

It's 99% of the time that this switch/tap has failed and leaks coolant allover the passengers floor.

Simplest solution ( after you have removed the heater box), is to junk the tap alltogether ( the arent cheap to replace either I might add ), and simply replace the tap with a short piece of copper tube (1/2 inch), add a couple of hoseclamps and reinstall the heater box.

Should take around 5 hours ........ have fun

Kingy

so y is there a tap to turn the water on and off???

i basically have it out and when i do is there anyway to check which parts leaking or just replace the hoses and tap with copper pipe?

if i replace this tap will there be hot air coming through the vents all the time even when i have it on cold or not??
i would really prefer not to have to rip the other car apart coz it has taken me like 2.5 hours so far

im gonna tackel the rest of it tomorrow morning and ill let u know how i went.

thanks for the reply guys been a great help

The tap stops water flow to the heater core, thats all it does !!!

By removing the tap water flows all the time through the core and so it is hot but its that way anyhow after a coup[le of hours of driving.... the water eventually heats up regardless of the tap being there or not.

There is a flap that also is activated when the controls are set to "hot", this flap changes the airflow direction in the heater box to flow through the heater core.
When the flap is set to "cool" on the controls it covers the heater core and air cant pass through the core...

So obviously you dont need the tap do you !

replace the tap only with copper pipe and fit new hoses from the tap area through to the firewall. Then with a couple of short pieces of copper pipes join up the existing heater hoses which go to the motor.
Its a pain in tha ass trying to bend the copper pipe around the back of the heater box to suit the firewall outlet..... I did mine this way and it took ages !

Kingy

i took the whole heater unit to my mates radiator shop and flushed all the mud out of the heater core and replaced a couple of hose clamps and checked all the pipes. There was a very minor hole near the top of one of the pipes that goes to the heater near firewall. so i put it all back together and it seems to be working fine now, fingers crossed

thanks for all the advice everyone

does it ever get below freezing temps where you live?? If so watch out...not sure about MQ/MK's but on G60's after a core rebuild they are known to fail again. And this is even when using the right anti-freeze mixture. Also on a G60 the fitting is on the top back of the block making it very easy to shut off the heater in summer. Perhaphs the same thing was in mind for the MQ fitting? Seems really dumb though where they put it....

I realise im too late with this post ( soz ive been busy ), But the way that i learned to check to see if radiators or heater units leak it to grab a bike tyre inner tube and cut it in the middle. Hose clamp one end to the bottom pipe of radiator then will it with water. Once full get the other side of the tube and clamp it to the top hose. Make sure the radiator cap is on.

Then get a foot air pump and plug it into the bike tube valve and keep pumping.
This adds pressure to the unit as if it was driving and u can find the leaks.

The reason i do this is cause half the time it only leaks under pressure not when water is just sitting in there.

My 2 cents worth.........

Screwy