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MG TF 135, Late 2003
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Discussion Starter #1
I recently bought a TF 135 having previously owned a R25 and ZS for a few years. I have always monitored engine coolant temperatures carefully and now find that the TF can be quite variable in comparison.
The engine heats up very quickly to the normal position on the gauge. Running temperature at steady 70 is around 92c but on slightly lower speed (55/60) and town/country driving at rises rapidly to and remains about 99/100c. On stopping it will increase rapidly a few deg more.

A few days ago I ran up the engine at idle speed only with heating control valve closed and recorded the temps

Time / Temp C
0 / 16
10 / 94 (Steady temp increase up to this stage)
11 / 96
12 / 98
13 / 99
14 / 100
15 / 101
17 / 102
18 / 103
19 / 104 Radiator fan auto ON
20 / 105
23 / 106
25 / 105
27 / 107
33 / 107 Heating control valve opened
34 / 92 Radiator fan auto OFF
36 / 97
37 / 98
43 / 98
44 / 97 (Engine bay fan on)
46 / 94
47 / 97
48 / 98 (Engine bay fan off)
56 / 104 Radiator fan auto ON

The radiator fan seemed to have little impact on the temperature, but the effect of the heating control valve was instant and significant.

It is a late 2003 reg manual at 48k miles, with cream coloured PRT, I assume original. There is little maintenance history but the previous owner bought it with HGF. An MLS gasket was fitted but nothing else was replaced as it had not been overheated. It has covered only about 3k since and appears to run perfectly. Everything seems in good condition.

Is this temp range and variation normal or should I carry out further investigation. Is this the correct PRT? Rimmers list different PRT temperatures for the TF, which I don't understand - 82 or 87 deg? Perhaps a leak sealant might have been used previously and has restricted the flow through the radiator?

Open to suggestions, tks
 

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TF135
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Yep, imo numbers seem ok but lethargy and heater control opening seems to verify your last sentence imo.
I think I'd remove the rad and at least thoroughly flush it. I've 'suffered' from rad leak products in the past and mine needed several (water-only) flushes.
The prt can get blocked by this stuff too. As far as I'm aware 82C is the 'normal' opening temp. I might be inclined to remove this and flush it out, too, although I didn't think of it at 'my' time...
(I thoroughly flushed the system - making sure it got warm enough to open the 'stat and circulate - several times, renewed my rad + took the opportunity to change to stainless coolant pipes when I realised my '05 TF had been bodged by leak-sealer. It seemed a d-i-y no-brainer at the time... :rolleyes:)
 

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MG TF 135, Late 2003
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Discussion Starter #3
Thanks for that. Yes, I was fearing a full cooling system strip down might be the best way forward. I really wanted to gauge how effective the radiator is on these cars given their location from the engine, and if my temperature range was normal or not.

As for the PRT, I have also previously read that 82C with soft spring was recommended but cant fathom out why 87C medium is also available for the TF
 

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TF135
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I'd say when you get it sorted keep an eye on those typical temps you've already experienced with your OBD connection. If you want to try to 'bomb-proof' further my current TF has twin fans and I've just read an article in MGCC mag about finding the yellow fan relay and (apparently quite easily) attaching an over-ride switch for the kind of super hot days we've had recently. Hmm...there are blanked off switch spaces in the console and I've got a couple of spare switches so I might look to get a spare relay first in case I break it...

ps I've just replaced a seemingly stuck expansion bottle cap which kept the system pressurized, coolant level low and temp very high for too long a time, ~4hours or so; imo this should be renewed at the slightest sign of coolant temp misdemeanors and (certainly for me) once a year.
 

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1995 MGF Mpi
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The temperatures you are seeing are fine, very typical values. I wouldn't be concerned.
 

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TF135
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Mowog73, I agree with the numbers; but look how quickly the heater circuit removes the excess heat when opened.
The reluctance to cool via the rad + fans would make me suspicious of (at least) some front-end malaise and the 'what-if' in me would fear a subsequent heater circuit blockage...
The extra cooling due to 70mph air pressure might arouse a few concerns in me as well. I think I'd be concerned enough to remove, inspect (and anyway) flush the rad - bearing in mind the cooling systems of our F/TFs have 'special needs' :rolleyes:
 

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1995 MGF Mpi
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I've read in one or more books on the F that the design of the front impeded cooling through the radiator.

Personally, I'm not surprised by the effects of the heater matrix on cooling. Small radiator but it has a dedicated fan.

I've had cars that were close to overheating and when you turn on the interior heater, it kept the car from overheating.

I live in a hotter climate than England (southwestern Ontario, Canada) and I've driven the car in 30 degC weather and never have had an issue with the F's cooling system, even with the a/c turned on.
 

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MG TF 135, Late 2003
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Discussion Starter #8
Here in central Scotland we have been struggling to get temps over double figures recently! Had a drive out today and discussed this with a pal who is also a part time mechanic. The car drives very well. He was convinced that there are signs that a leak sealant has been used previously and so confirms that a cooling system strip down would be best option sometime soon.

Does anyone have a further view on the PRT side of things as I will probably end up replacing that too?
 

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TF135
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...stained coppery expansion bottle, I bet...:( I got mine in the washing up bowl and removed lots of it with a brush. I also tried shaking it vigorously with a rice + washing detergent mix.
I wonder if this'd be the time to invite input/advice from those who've successfully cleaned out their F/TF systems with dish-washer tabs?
re prt. It seems to be working ok and might get cleaned up ok, but if you get as far as removing it you might as well bite the bullet and renew - unless it cleans up 'as new' imo.
 

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MG TF 135, Late 2003
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Discussion Starter #10
Though the expansion tank is fairly clean there is very slight signs of copper inside the cap.

I have previously cleaned out tanks with gravel and tried a fair cocktail of other chemicals, but less clear about what is effective to run through the system.

Replacing with the correct PRT still bothers me, and why Rimmers offers 2 different temperatures for the TF?
I recently installed an 82C PRT to a ZS. It lowered the typical running temp by about 2C to 87/88c
 

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MG TF 135, Late 2003
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Discussion Starter #11
Update, I stripped down the cooling system today after adding a basic dish washer tablet to the system for cleansing. It didnt make much difference to what drained out which was fairly clean despite clear evidence of k-seal having been used previously. Probably should have used more than 1 tablet!

Water flows well through the radiator and pipes and heater. However the PRT was clearly past its best with the internal rubber seal well damaged and partly missing. There must be a wee bit of it left around the system somewhere. I decided to break it apart to see what opening temperature was stamped on the thermostat - it was 82C and the spring felt quite soft in comparison to others I have tried. I am sure it was the original fitment with a manufacture stamp of July 2003 on it. It least I now know what to replace it with.

I need to replace one hose section which is weakened and fit s/s underfloor pipes. I think I will also replace the radiator as the fins are very brittle and generally suspect.

I have obtained a replacement expansion tank with a sensor built in. On previous cars I have just installed a wee neon flashing light with a switch which I run off a 9v battery. Saves messing about with car electrics which I know nothing about!

Hopefully a greater level of confidence after this is done.....
 

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Your temp numbers are very interesting. Thanks for providing. My head temperatures can vary (at warm) between 93 C and 101 C (oil steady 96 C). I have a thermostat that opens at 75 C which is located on the outlet pipe just before it enters the tunnel.

As an aside, I am not sure a remote thermostat makes much difference whether it opens at 75, 82 or 88 C. I fitted the 75F thermostat as that was the advice in the days before the cooling issues were fully understood. The standard thermostat for the MGF is I believe 88 C.
 

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MG TF 135, Late 2003
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Discussion Starter #13
I have now replaced the PRT (with 82c soft spring), radiator, underfloor pipes and one suspect rubber hose. Flushed out the system as best as poss and there was very little debris found.

Again, I have monitored the temperature on start up from cold, idle only, with heater valve closed. Over a period of 17 minutes the temperature increased steadily from 10c topping out at 95c and remained steady thereafter. On opening the heater control valve it dropped immediately to 84c before slowly increasing again. No cooling fans came into operation.

While out driving at steady high speed the temperature was maintaining around 91c so perhaps a degree or two lower than previous. During town/slow driving the temperature was being maintained significantly lower - more in the region of 93-94c

Clearly I am well pleased with the results and attribute this mainly to the new PRT. There was no sign of blockages anywhere else in the system.

I found a another 2004 TF at a breakers nearby and had a look at its PRT. It was exactly the same as mine had been - cream 82c, probably original, so think this must have been the standard fitment at the time, Its internal seals were totally shot too.

Fab result and one thing less to be concerned about.....

Had the car successfully MoT'd a couple of days ago. A rear brake pipe burst during the test, high up in the arch and a difficult area to spot. That was a fortunate outcome. Also had the wheel alignment checked/adjusted and the car is now much better controlled at high speed.
 
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