Coolant loss

[Trimmtrab]

Hello,

My 2006 XC70 D5 recently came up with the Low Coolant warning the other day when I was driving, I pulled over and checked and it was below the low marker by a couple of mm, I kept my eye on the temp gauge and limped it home, when I got near home the coolant warning disappears and when I get home life the bonnet and see the coolant is above the “min” marker where it should be. I topped it up the next day and when I removed the cap I got a slight hiss of air. I’ve been driving it now and it’s gone down again slightly. I checked it yesterday morning and today, I took the cap off this morning and got the hiss and the coolant level rose slightly.
I thought I had a bit of a leak on my road the other day but I haven’t seen anything since.
Only other issue is the heater doesn’t blow hot, it’s going back to the garage who I bought it from on Friday for some unrelated issues to be fixed.
Any ideas what could be causing this? There are no leaks in the interior so not sure if it’s the heater core.

Cheers Greg

[cheshired5]

When up to temperature, do the heater pipes in the engine bay get equally too hot to hold?

[Trimmtrab]

Originally Posted by cheshired5

When up to temperature, do the heater pipes in the engine bay get equally too hot to hold?

Hello,

Just checked after a big drive and they are warm but not hot, I can hold them easily enough without discomfort.

Cheers Greg

[cheshired5]

Check the radiator top hose coming off the thermostat after a decent drive.
If that is too hot to hold, then the heater matrix is likely blocked either by a physical blockage or a collapse inside.
If you have even cheap diagnostics to get the exact coolant temperature, that will be a help also.
Other suspect areas for the leak are discussed in this thread.

[Trimmtrab]

Originally Posted by cheshired5

Check the radiator top hose coming off the thermostat after a decent drive.
If that is too hot to hold, then the heater matrix is likely blocked either by a physical blockage or a collapse inside.
If you have even cheap diagnostics to get the exact coolant temperature, that will be a help also.
Other suspect areas for the leak are discussed in this thread.

Brill, I’ll check the temps tomorrow evening after work.

I’m just hoping it’s not a head gasket failure!

Cheers Greg

[cheshired5]

Originally Posted by Trimmtrab

I’m just hoping it’s not a head gasket failure!

Almost unheard of on a D5 and the symptoms you do have are much more likely to be a result of something else.

[Trimmtrab]

Originally Posted by cheshired5

Check the radiator top hose coming off the thermostat after a decent drive.
If that is too hot to hold, then the heater matrix is likely blocked either by a physical blockage or a collapse inside.
If you have even cheap diagnostics to get the exact coolant temperature, that will be a help also.
Other suspect areas for the leak are discussed in this thread.

Checked last night and again its warm but not hot enough for discomfort.

Cheers Greg

[cheshired5]

Right, well you need to be doing the physical checks mentioned in the other thread I linked and we need precise coolant temperature info too.
You could need a new heater core, thermostat, pipework or a combination of the above.

Do you have any exhaust smoke of any colour?

[Trimmtrab]

Originally Posted by cheshired5

Right, well you need to be doing the physical checks mentioned in the other thread I linked and we need precise coolant temperature info too.
You could need a new heater core, thermostat, pipework or a combination of the above.

Do you have any exhaust smoke of any colour?

Its going to the garage later this week so will check when its on the ramps. I don't have any diagnostic software so will have to source one.

No smoke of any colour

[cheshired5]

If you have a multimeter, pulling the ECT plug after a decent run and getting the resistance reading between the coolant sensor pins could be enough.