Topic

Since I replaced the underfloor pipes with stainless, I’ve been having overheating problems.
When I replaced the pipes, I flushed the system out with dishwasher tablet powder, bled it 3 times and the water pump was replaced just over 1000 miles ago.
My 2002/3 MGTF 160 runs for about an hour with the water temp just below the middle (heater turned off) then then needle goes to ¾ fan comes on at just over ½.
Turning the heater on drops the temp immediately, so the flow would appear to be OK.
The header tank fills to overflowing, but drops back fairly quickly after I turn off the engine.
I’m in the middle of fitting aircon, and the aircon rad is quite big, and just in front of the engine one, would this be sufficient to cause overheating, or should I be looking elsewhere ?

The airflow through the radiator is very poor on the TF to start with, but on models with factory fitted AC the standard condenser rad is fitted in front of the coolant rad anyway so it must work.

If you have the TF standard AC condenser rad then it should allow sufficient air flow to the coolant rad, if it’s 3rd party condenser then matrix could give you a reduced through flow to the coolant rad.

The coolant circulation around the heater is on the engine side of the thermostat so it’s not an indication of circulation around the rad. You need to get the system hot (thermostat open) lift the front of the car and with the engine running (pump running) check the 2 rubber coolant hoses that run above the subframe to the rad. If the thermostat is allowing circulation then both rubber hoses will be hot (albeit the one on the out flow of the rad slightly cooler) If one is hot and the other cool (or both cool) then no; or poor circulation. If your system has been cleaned so you have no restrictions in the circuit it may be the thermostat or you could still have air in the system.

Check that the small hose that runs from the inlet manifold to the top of the expansion tank is clear as there is a small valve in the inlet manifold which perpetually bleeds any air from the engine to the header tank, that can get blocked. With the expansion cap off (cool engine) remove the small hose from the top of the tank and you should be able to blow down it to make sure it’s clear.

Brian.

Thanks

I've cleaned the jiggle valves, only get flow through the top pipe slowly, but I noticed that although the metal pipe with the bleed valve is hot, the other, thinner metal pipe is not.

Tried squeezing it, and got a bit of air out.

Is this the one which goes to the thermostat, in which case will the stat have jammed (2002/3 car with old system )

I understand they are a pig to get at, after removing the stat am I better replacing the plumbing with the later type ?

Aircon is off an 03 stepspeed, standard Valeo aircon rad, so this should not be the problem.

mgbv8mike wrote: wrote:

Thanks

I've cleaned the jiggle valves, only get flow through the top pipe slowly, but I noticed that although the metal pipe with the bleed valve is hot, the other, thinner metal pipe is not.

Tried squeezing it, and got a bit of air out.

Is this the one which goes to the thermostat, in which case will the stat have jammed (2002/3 car with old system )

I understand they are a pig to get at, after removing the stat am I better replacing the plumbing with the later type ?

Aircon is off an 03 stepspeed, standard Valeo aircon rad, so this should not be the problem.

Both the steel pipes that run around the engine block go back to the thermostat housing (return flow) one has to go through the stat and the other by-passes it but I am not sure which.

On the image below item 7 is the thermostat housing.


I would definitely retro fit the later system with the pressure relief thermostat as it's supposed to reduce thermal shocks to the engine block and head.

Here is an interesting article from ultimatemg on thermal shock with the K series engine:
http://www.mgf.ultimatemg.com/group2/common_problems/hgf_pages/why_do_hgfs.htm

Below shows the earlier and later (PRT) setup.


You are correct in saying that the thermostat housing is very difficult to access due to it being covered by the inlet manifold; but it can be done it in situ as I have changed both the O rings on the housing due to a coolant leak.

Brian.

Thanks Brian.

It's pipe 10 that's not warming up, it would suggest that the thermo is still closed.

My car is a Tf160 with the oil cooler, I understand that adds a further dimension to the job.
Did you remove the inlet manifold , or go in blind ?

Mike

I did it with the inlet manifold in place:

How-To

But if I ever have to do it again I'd remove the manifold. That's a pain also but gives much better access to all fixing points.

Thanks, I saw your 'how to'

Two questions :-

I've got a pit in the garage, will it be easier from underneath ?

Did your car have the oil cooler, I understand it masks the bolts ?

I'm seriously considering the post 03 upgrade pressure thermostat, , parts prices are not exorbitant, and it's clearly an improvement on the old system.

I'm fitting aircon, and have the compressor to fit and alternator to move, will be doing this at the same time, looks like my week's spoken for !

mgbv8mike wrote: wrote:

I've got a pit in the garage, will it be easier from underneath ?

Did your car have the oil cooler, I understand it masks the bolts ?

iirc something covers the access from underneath and you cannot access all items from there. Maybe someone can confirm?

I've no oil cooler, not sure if it masks the bolts completely or just makes access even more difficult. Someone else?

Bertl wrote: wrote:

mgbv8mike wrote: wrote:

I've got a pit in the garage, will it be easier from underneath ?

Did your car have the oil cooler, I understand it masks the bolts ?

iirc something covers the access from underneath and you cannot access all items from there. Maybe someone can confirm?

I've no oil cooler, not sure if it masks the bolts completely or just makes access even more difficult. Someone else?

No chance from underneath as the exhaust pipe, subframe and driveshaft are in the way as below:



If you have the ABS plastic inlet manifold you can unbolt it and position it out of the way (don't try to remove it from the engine bay unless you can do a Rubix cube in the dark with one hand tied behind your back) If you have an alloy manifold you can remove the top section easily, but the lower section has 2 bottom outer nuts which can be a bit of a challenge to remove.

With the inlet manifold out of the way it's a breeze.

Brian.

Thanks Guys,

Cast manifold here.....so manifold off it is then......from the top evidently.