MGTF Cooling System issues after HGF

[DJM]

As some people will know, my TF has had HGF and has been in shop for some time.
Thought all was fixed, but garage having issues with the cooling system.
Chap who is doing the work is ex MG trained and has been doing the F/Tf for many years. He has vacumm fill and also does the usual cap off checks.

History

1) had major cam belt service and at same time had remedial work of new water pump, under-floor (SS) pipes and low coolant alarm.
2) at time service being done, garage screwed up and buggered piston, con rod etc etc forcing a head off and a new HG fitted.
3) Returned from gagrage with a water leak
4) Lots of cost later (and obviously different garage and DIY) we found the leak and fixed it. Current garage did a service and re-bled coolant to remove air.
5) Recently had HGF
6) TF into garage for MLS HG (finding in the process that the original gagrage had fittied an HG older than the TF), new cam belts (well do it while the heads off is minimal cost)
7) garage flushed car and on final check found a thermostat issue.
8) Thermostat replaced, problem not solved
9) Radiator checked by replacement with another borrowed for a few hours - problem did not go away
10) Thermostat removed and checked and found to be working
11) jiggle valves checked and free
12) coolant pipes flushed and air blown where possible
13) Water pump impellor checked by hand and appears ok
14) oil cooler bypassed and definitely a contributer to the problem.

Car will now run and idle happily enough with the fans kicking in and out as expected. But the final acid test of removing the expansion cap fails with coolant boiling up and over the top.

Pretty much run out of ideas of what to try next.

Coolant definitely being pumped around the system (though I suppose it could still be the pump if it's not generating sufficient pressure). Jiggle valves appear free, water entering and exiting rad. Thermostat checked. Some pipes changes. All pipes flushed and items air line cleared. Garage has more than 10 years experience of K series and has never seen this before. He has asked everybody in the trade he can think of and got no useful replies.

Anbody think of Anything else he can try?

[mgtfnut]

Two things spring to mind.

If I read you correctly But the final acid test of removing the expansion cap fails with coolant boiling up and over the top. is asking for trouble. I may be confused, but removing the header tank cap when fully up to temperature is folly - the coolant will boil throughout it's volume, inducing steam/air pockets. This is scientific fact It is not a good idea to ever remove the cap when hot, engine running or not.

Are you sure the thermostat is round the right way? It may appear odd, but the bulb is facing away from the incoming coolant. The smaller by-pass pipe comes into the thermostat housing at 90* directly onto the bulb and controls movement of the valve.

Also you say you by-passed the oil cooler. Is this a TF160 model? If it is, did you by-pass the intercooler bit itself, and did "it" get better or worse? What exactly is "it". The oil/water intercooler is made by KTM of Austrian bike fame and has very fine orifices for both fluids. Perhaps either/both fluid channels are obstructed?

Just a few thoughts, as I spent a few weeks this summer re-plumbing my TF135 with a TF160 oil cooler and sorted out a better preferential water flow for the heater amongst other things. I don't have the thermostat problem as such, as I've fitted a PRT under the washer bottle.

[cayote]

Hi board, my prob is that the radator fan is constantly running i dont think this ment to be!!should i disconnect it?? any ideas, thanks

[David Clelland]

Hi board, my prob is that the radator fan is constantly running i dont think this ment to be!!should i disconnect it?? any ideas, thanks

If you have a bad connection at your temp sensor or the temp sensor is not working the default is for the fan to run all of the time.

[cayote]

Hi Thanks for that so where do i find sensore??

[Charless]

Cayote,
On the elbow here:-
http://www.mgfcar.de/sensor/ECU_dcp_3953.JPG
If you know what a multimeter is; Dieter also gives the expected resistances to prove whether the brown sensor is US, if you don't know, don't ask, just replace the sensor for about £15 from xpart dealers. I need to be doing so shortly too.

[plrobbo]

Hi DJM - As 'mgtfnut' has said is all very correct. Interesting question is, as he's also asked, what year is your car and is it a 160?
If it's a 2003 onwards it should have a PRT (thermostat), and only 160's have oil coolers. I ititerate what 'mgtfnut' has said about taking the cap off while hot BUT it is also normal for the level of water to rise in the tank even when just warm - air is then induced into the system and you'll have to bleed it again - Never remkove the cap unless the engine is totally cold. Cheers Robbo.