Re:Cooling system/ cold heater problem

2004 TF 135 - my daughters car, her daily driver. The story from the beginning
Clutch diaphragm collapsed. After some searching found a local garage to replace the clutch in a reasonable time frame and cost.
Got them to change cam belt and water pump at the same time.
Car returned with working clutch but with coolant leak. Back to the garage for 3 days “ replacement “ part needed, no extra charge.
Since then unable to get the heater to blow hot.
Read all the forum(s)
So, bled the system from all three points three times. Run 2.5 litres of coolant through the heater bleed nipple.
Run the engine to operating temperature, gauge mid scale, both main pipes at front and radiator get hot, radiator cooling fan kicks in cools rad and drops out. Gauge still mid scale.
Checked heater control operates valve by observation. Heater pipes get warm felt through ash tray hole in centre console.
Turn on fan, blows Luke warm for a short time then blows cold, obviously cooling the matrix.
Expansion tank level rises with temperature.
Does not seem to be any coolant flow in the tank when the engine is running, is that correct?
Is it possible that the “ replacement part” has been incorrectly re-piped? Not sure at this time whether this was the 4 way connector or PRT.
Any assistance much appreciated. Don’t know where to go next. It can’t be that difficult.

Expansion tank level rises with temperature.
Does not seem to be any coolant flow in the tank when the engine is running, is that correct?

Rising coolant level strongly suggests air in the system still, the only other reason would be a failed head gasket.

There should be constant flow through the header tank, entering via the long thin 'overhead' hose and out through the bottom hose. So this suggests there is an air block and/or that overhead hose is otherwise blocked. There is a jiggle valve on the return hose at the cylinder head. Is it flowing coolant?

When up to temperature, the heater pipes within the centre console should be too hot to touch, so either the coolant is not flowing correctly or the heater valve is only partially open or failed. It is also possible for the cable connecting the heater dial to the valve to have slipped so that the valve doesn't open. You need to remove the driver's side kick panel to see if the valve is fully opening.

Did you get good coolant flow from the engine pipes bleeder. Sometimes these are clogged and need cleaned with a wire inserted.

Thanks for your response.
There is no apparent loss of coolant or evidence of coolant in the oil.
I got a good flow of coolant from the engine bleed and from the radiator and heater bleeds.
I checked the heater valve operation behind the kick panel from the control knob. Lever travels through 90 degrees easily.
The main radiator pipes get hot and the temperature gauge never goes above normal reading so the main flow through the radiator appears OK. When the cooling fan cuts in it cools the system fairly quickly and cuts out
How do I check flow through the jiggle valve. There is clearly no flow through the header tank.
The system was OK prior to the repair and the fitting of the part that must have been broken during the clutch replacement.
I can only imagine it was the 4 way connector or the PRT that was broken.
I have read in one forum that the connector can be piped up incorrectly or be faulty. Is that possible or likely?
Are there any images of this area available so I can check the pipe connections.
Thank you for your input. Can’t let this beat me.

On Rimmer Bros webpages you can see a 3D sketch of the hose systems for both pre PRE and post PRE thermostats and images of the individual pieces. I agree it is complex and takes some time to "get the eye in" to work it all out but it is there. Other images on MG Obsession

A couple of things that might help you.

As David says, the return to the expansion tank is through the small tube at the top right of the tank. The best way to check it is to remove the cap when the engine is cold and then start the engine up. You should be able to see the coolant freely flowing into the half-full tank. If you can't, something is wrong.

As for the coolant level in the tank, the scientist in me means that I am going to have to disagree with David (I never thought I'd find myself doing that!). The expansion tank is exactly that, it allows for expansion of the coolant. Water expands when it is heated. It is not compressible. Air, on the other hand, is highly compressible (think of your tyres). As the system heats up the coolant expands and the air is compressed. This is why you must not overfill the tank with coolant. If the engine and coolant get too hot, the expansion of the coolant compresses the air to the point where the pressure cap will release.

As the system cools, the coolant should drop to its original level, If it doesn't then, yes, there is a problem.

Just a thought, if the water pump was changed, is it working? I had similar problems on my Daughters Polo, not the same as Rover, but the VW had a plastic impeller and it had detached from the shaft, so the water was static and causing over heating due to lack of flow.

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"Caveat" I have not had cause to work on the coolant system (yet) so do not know a lot only what I've read.

I think the OP should return to the garage to discover what part if any they replaced, if it was the 4 way connector I believe this is also called the heater bypass which might be a clue, perhaps it was "bodged" rather than replaced.
I also think I read (ie can't find) a thread somewhere that mentioned a restrictor? in this part that can come loose (anyone?), please feel free to shoot me down it will help me learn.

Yes, there is an internal hard plastic restrictor that can become detached and often will end up at the union between the hose and the metal engine pipes.

This happened to me and the restricted flow caused the 4 way hose to split apart catastrophically. This was on my mk2 F. The TF has a differently configured 4 way setup, with a plastic 4 way junction connecting separate hoses.

I believe the two versions are interchangeable.

EDIT. It appears that the different configuration is associated with cars fitted the PRT system from the factory.

Update on the saga of the cold TF heater.

As suggested I returned to the garage to confirm that the 4 way connector was the part replaced.
They agreed to investigate further.
The mechanic test drove the car and found that the luke warm heater went cold after a short drive time. After discussions and reference to the online diagrams and information we agreed that when the PRT opens then the hydraulics of the cooling system robs the heater circuit of flow.
The 4 way connector was removed which revealed that there was no restrictor fitted.
The garage referred to the part supplier a respected MG specialist and parts supplier who said that they used the connector with no restrictor with no problem.
It was decided in view of the online advice a restrictor was devised and fitted.
The cooling system was refilled.
I carried out a test drive, 20 miles local roads, traffic and a motorway section.
Everything seemed now to be normal. Coolant and oil temperatures as expected. Heater working and hot.
The fans did not kick in some traffic.
Thanks to all who have contributed with advice including those on past forum streams.
Thanks to the garage. Respect to them for undertaking the investigation and work at no additional cost.
It just leaves me with one outstanding question?
The MG specialists seemed to say the restrictor is not needed but without it our car did not operate as it should. The advice from other users is contrary to this.
Clearly there are images of the restrictor from past parts.
So who is correct.?
Thanks

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