Heater - No flow into heater D5

[SwedeXC90]

Vehicle is a 2007 XC90 D5, Australian delivered.

Wondering if anyone has had an issue where no coolant is flowing out of the engine into the heater core? Long story short, heater went cold with only minimal heating and started to investigate - it does get to 7 degrees in the winter here you know, brrrr! Undertook a comprehensive clean of the heater element thinking it was blocked and have now concluded flow through the core is perfect. Turned heater knobs in cabin to hot first although as the system is a full flow can't see what that would do but did it anyway. Then fabricated long hoses to route the heater inlet from the engine into a bucket and from the bucket into the heater return into the engine and ran the engine making sure the expansion tank didn't run dry. Result of this was that there was no flow out of the engine - well a trickle at most which was hot but there was nowhere enough of it to circulate around the heater core and heat the air. Interestingly flow increased to the heater when i took off the expansion tank cap and basically stopped when i sealed the system by putting the cap back on.

So, anyone know if there is any sort of heater control valve or flow obstruction device up stream of where the heater feed goes into the heater core? I have a submersible USB inspection camera ready to send to perform a colonoscopy of the heater hose that feeds the heater core to see what's up there and if there is anything blocking it. Only other thing I can think of if there is any connection to the heater supply from the thermostat?

As an aside, to clean the heater element I bought a $45 pond pump, low pressure and connected to the inlet of the heater core and the return into a 20l bucket. Used a liberal portion of CLR (calcium, lime and rust) dissolver and circulated for a few hours. A few bits of calcium flake came out but overall very clean. Ran clean water from the hose through it to make sure none of the CLR was left in the system and now confident it is as good as new, pic's attached.

Thanks

[cheshired5]

Is the car still on the original timing belt driven coolant pump?

[SwedeXC90]

Yeah still the original water pump, at 198,000 km’s. Changed the belts at 130,000km’s but didn’t do the pump as thought that can wait till I do the belts again soon. Are you thinking that the impeller has spun off or something? The car in all other respects is fine and handles the hot WA weather here no problems so can’t imagine the water pump isn’t working. Always had factory coolant in it as well so corrosion should not be an issue.

[cheshired5]

To aid with finding a possible flow restriction, this is the cooling system description from Vida for the D5244T4 engine.....

The bearing housing in the turbo is water cooled. It cools the turbo even after running at hot operating temperatures and when the engine is switched off quickly, as the coolant is self-circulated by the heat in the turbo.


The coolant pump pumps coolant around the coolant casing of the first cylinder. A plate in the casing divides the coolant between the first cylinder and the oil cooler.


The coolant then flows backwards in the engine block and is divided diagonally in the slits between the cylinders and further up the channels around the exhaust valves. Hotspots, particularly around the valve seats for the exhaust valves, are transported away, which gives more even temperature.


After having left the cylinder block the coolant is led around the pipes for exhaust gas recirculation (EGR) on to the passenger compartment heating element and then back to the thermostat housing and the coolant pump.


The shut off valve is located in the inlet pipe from the thermostat housing to the expansion tank. This limits the coolant flow to the expansion tank when the engine is being run to operating speed.


The bypass valve is located between the coolant outlet on the cylinder head and the feed line to the coolant pump. This restricts the coolant flow to the coolant pump when the engine is run hot.


Most of the coolant is fed to the heat exchanger and flows back to the coolant pump via the EGR cooler.


The bypass valve begins to open at a certain coolant temperature. It remains open until the engine has reached operating temperature.


Once the engine has reached operating temperature, the thermostat and shutoff valve are fully open and the bypass valve is fully closed. At this point, the large coolant circuit is open.


The time required to warm up the engine is reduced and the cab temperature can be increased more quickly by using the shutoff valve and bypass valve.


The bypass valve and shutoff valve are controlled by the engine control module (ECM).


Coolant circuit
The flow of coolant is dependent on the following components:

Bypass valve
thermostat
shutoff valve
engine temperature sensor
engine control module (ECM)

Due to the high efficiency of the diesel engine and thus relatively small heat losses, there may be problems with maintaining a comfortable temperature in the cab when the outdoor temperature is low. The job of the various components is, on the basis of the coolant temperature, to control the flow of coolant to the heater element in the cab so that the coolant heats up as quickly as possible.


Warm-up phase, thermostat closed
The thermostat and solenoid valve are closed while the engine is warming up. At the same time, the bypass valve keeps the link from the cylinder head to the coolant pump closed.
The coolant circulates in the small circuit only, from the cylinder head and from the oil cooler to the heat exchanger in the cab.
When the engine coolant temperature rises, the bypass valve opens the connection to the coolant pump in proportion to the temperature increase. The coolant now flows to the heat exchanger in the passenger compartment and the inlet for the coolant pump. The thermostat and solenoid valve are still closed.


Thermostat starts to open
When the thermostat starts to open, the bypass valve closes the link between the cylinder head and coolant pump proportionally.
At the same time the solenoid valve gradually opens the link to the expansion tank. The flow from the cylinder head is now divided to:

the cab's heat exchanger
the inlet for the coolant pump
radiator
expansion tank

Engine has reached correct operating temperature
Once the engine has reached the correct operating temperature, the bypass valve completely closes the link between the cylinder head and the coolant pump. At the same time the solenoid valve completely opens the link to the expansion vessel.
A small amount of the coolant now flows through the cab's heat exchanger while the large flow takes place via the radiator.

[cheshired5]

Originally Posted by SwedeXC90

Are you thinking that the impeller has spun off or something?

No. If the pump is the original, that would be the last thing I would consider causing a problem.

[SwedeXC90]

Thanks a lot for the VIDA run down of the cooling system. I am in the process of finding pictures of the engine on the net and re-creating the flow based on the description above. Not easy but should be able to put it together.

1) The shut off valve located in the inlet pipe from the thermostat housing to the expansion tank and
2) The The bypass valve located between the coolant outlet on the cylinder head and the feed line to the coolant pump

are the first things I will start looking into. As these are both controlled by the ECM there could be an issue with that although I will start with mechanical issues first before going down into the electronics. Temp sender also provides input so may look into that but there is no other indication of issues with this.

If I read the description correctly the thermostat is independent of the water circuit that feeds the heater element so will leave that alone for the time being.

An pain but an interesting problem that I am keen to unravel.

[SwedeXC90]

OK, had a good look around and I am none the wiser as to what and where the coolant shut off valve and the coolant bypass valve are in the system. An extensive internet search reveals not a lot but did manage to get some good images so if anyone can point me in the right direction, please feel free to point them out in the attached photos.

[oragex]

Maybe there is quite some lime deposits from a previous owner using tap water, which would block the flow from circulating properly.

Maybe try a Prestone flush mixed with distilled water (we get this water from pharmacies here), read the instructions by peeling the sticker off the bottle

https://www.amazon.com/Prestone-AS10.../dp/B00B99U088

[Chr15topher]

What was the outcome? Solved?

I just changed the heater matrix in my 07 XC90 D5 Auto. Got the car hot. Ali pipes to matrix were stone cold. Pipes to bulkhead in engine bay were hot. Alas, no hot air in cabin. Pulled the ali pipe from matrix and nothing but air! WTF?

[BestGear]

Our MY2005 is pretty much the same - heater never heats enough to defrost the windscreen if left idling, however, drive it a mile and the heater is roasting.

I have flushed the whole system a couple of times, thermostat and water pump changed... no difference.

Just live with it now.