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Discussion Starter · #1 ·
Hello wise MGF/MGTF owners.

My trusty 2002 MGTF160 whizzes along majestically. But as winter draws in, I wish the heater worked a bit better. When I got the car in April, the heater barely seemed to work at all, but I wasn't bothered because the weather was warm!

I recently flushed the old coolant out, including lengthy spells with the hosepipe. Then I filled the system with 50% OAT 50% water. Then I bled the system repeatedly, using the heater bleed screw, radiator bleed screw, and the infernally awkward bleed screw in the engine bay, until there was clear blue water (orange water really) coming out of each. The car's been driven up to temperature probably a dozen times since then, the level in the expansion tank stays the same, the coolant gets up to 95 degrees centigrade.

I've taken the panel off from the driver's footwell area to check the heater control mechanism - it's working as it should.

With the engine fully warm, but idling, the heater produces no heat. Going along at 70mph and 3000rpm or so, the heater produces reasonably hot air (not boiling but more than warm). Below 2000rpm it's basically cold.

Does anyone have any suggestions for fixing/ diagnosing this issue? Airlock? Blocked matrix? Something else?

Thanks all in advance
 

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Some good suggestions already.

I still suspect that you might have some air in the system though. Two things:
  • When you bled it was the heater set to hot?
  • Trying having the engine running with the coolant cap removed when you bleed it.

Good luck
 

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Discussion Starter · #5 ·
Hello, thanks for the replies.

1) I've not seen the thermostat, but the engine warms up swiftly and stays at a steady temperature on the dashboard gauge & Torque app so I don't think the coolant is cold. I've had the engine idling with Torque saying the coolant's 95 degrees celsius and the air from the heater still blowing cold.

2) The fan is working correctly on all speed. When I bought the car in April this year the fan didn't work on speeds 1 and 2 so I replaced the resistor, having been kept cool in the summer I now want to stay warm in the winter :D

3) Yes I bled the coolant system with the heater set to hot. I bled it once with the coolant cold, and then after returning from a long run I bled it again with the coolant hot. I haven't done it with the engine running though.

My plan is to try to bleed the system once more. I'll do it with the engine running, heater set to hot, coolant cap off, and I may even raise the rear of the car to encourage it even more! I'll report back with my progress in due course...
 

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I haven't done it with the engine running though.
Without the engine running the coolant pump isn't circulating the coolant and/or any potential air trapped in the system. I would suggest that that is your issue right there.
 

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MGF's x 5 MGTF's x 6, Rover 620Ti & Cortina Mk3
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Had exactly the same issue with one of my TF's, not sure if its the matrix blocked or perhaps the heater valve, or possible head gasket failing.....the head gasket has failed on the thing a while ago now but not got around to sorting it to see if the change of head gasket resolves the heater problem...one of the problems with having a number of F's & TF's available, you just swap to the next one rather than fix the problem :p
 

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Some later cars had a SAAB valve, aimed at getting a faster warm up, which if failed bypasses the heater. If your model has a SAAB valve, I’d advise checking it...

 

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Some later cars had a SAAB valve, aimed at getting a faster warm up, which if failed bypasses the heater. If your model has a SAAB valve, I’d advise checking it...

This post is to do with an MGF heater valve. Not a Rover 25.
 

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Discussion Starter · #12 ·
Hello everyone, thank you for the further replies and apologies for my delay in responding. I conducted a re-bleed of the system this afternoon with the engine running. My actions were:

1) Removed expansion tank cap - coolant level is correct and coolant looks completely clean
2) Set heater to maximum heat
3) Started engine, left it idling for ten minutes
4) Opened heater matrix bleed valve - coolant sprayed out in a consistent flow, it was cold. After five seconds of uninterrupted flow I closed the valve
5) I put the expansion tank cap back on and left the engine running until the coolant reached 94 degrees centrigrade (measured using Torque app - dashboard gauge also reached usual level)
6) Opened bleed valve again, coolant sprayed out consistently again, still cold

At no point was the air being blown into the cabin remotely warm.

It's like the coolant is not being properly circulated around the matrix, even though there is evidently enough pressure in the matrix to spray coolant out of the valve when opened.

If anyone has any theories about why hot coolant from the car's engine & radiator isn't making its way through the heater matrix, and what I should do to remedy this issue, I'd be grateful for your thoughts - until then I'll continue with thick jumpers, and move onto scarf and gloves when driving as winter draws in :D
 

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Discussion Starter · #13 ·
After some research I have a theory. I think there's supposed to be a coolant flow restrictor in the coolant circuit and my car is missing it. I got this idea from an old post on the t-bar forum.

Someone on that thread wrote "It's a flow restrictor for PRT models. Without it your heater doesn't blow warm air unless you are revving above 2500rpm approx. Something to do with moving the thermostat out of the head. I retro fitted my F with a PRT and I should have fitted the restrictor as my heater doesn't get warm."

The restrictor seems to be a small piece of plastic that goes into a 4-way plastic piece like this one, and shown in-situ below:

Automotive fuel system Gas Auto part Automotive exterior Metal


So I'm formulating a plan of action. I need to locate this 4-way plastic piece on my car, take the hose off, and see if there's a restrictor in there. If there's not, I can then obtain one, fit it, and hopefully the heater will become hot. So now I have two questions:

1) Where is this 4-way piece exactly? Has anyone sighted it, and can suggest the best angle of attack? "Sometimes, he’ll come in at an angle. Other times, he can hover, then swoop. Sometimes he can even come in from beneath, like a worm, or mole. The Lord, it’s his call how he chooses to manoeuvre."

2) If the restrictor does prove to be missing, where might I obtain a new one? Rimmer Bros evidently sell the 4-way piece, but I can't find the restrictor for sale anywhere. I'm sure it would be possible to bodge a DIY restriction somehow but I'd want to tread very carefully given the HGF cliche with these cars.

N.B. my car is a 2002 MGTF VVC which has had 3 HG replacements in its life, and the seller assured me it's had the stainless coolant pipes (which I've seen with my own eyes when under the car) and relocated thermostat (which I've not verified).

Anyway, comment away, I'll continue pondering and if I make any progress I'll post it.
 

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Putting the restrictor valve to one side for a moment - why did you not bleed through the other two points as well? There is one in the engine bay and one at the radiator.

By only bleeding from only one point, you leave the very real possibility of air still being in the system.
I would suggest that while that possibility remains, you should not move ahead with any other potential fixes.

Good luck.
 

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97 BRG MGF. 2009 SKODA SUPERB.
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Putting the restrictor valve to one side for a moment - why did you not bleed through the other two points as well? There is one in the engine bay and one at the radiator.

By only bleeding from only one point, you leave the very real possibility of air still being in the system.
I would suggest that while that possibility remains, you should not move ahead with any other potential fixes.

Good luck.
I agree entirely with what IanMc has said.
 

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Sorry gentlemen if you look at the original post #1 the OP says "Then I bled the system repeatedly, using the heater bleed screw, radiator bleed screw, and the infernally awkward bleed screw in the engine bay, until there was clear blue water (orange water really) coming out of each" so he has bled all 3 points and got a good stream out of each.
 

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Sorry gentlemen if you look at the original post #1 the OP says "Then I bled the system repeatedly, using the heater bleed screw, radiator bleed screw, and the infernally awkward bleed screw in the engine bay, until there was clear blue water (orange water really) coming out of each" so he has bled all 3 points and got a good stream out of each.
Understood - but according to post #12, that it wasn't done last time around.
 
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