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MG MGF Technical - Thermostat Disaster

Hi folks,

I went to fit a new thermostat over the weekend, with the help of full instructions from the RAVE CD and an 8mm ratchet spanner purpose bought.

My ’96 MPI had a new ’01 engine fitted about 3 years ago and it appears that the butchers that killed the old engine and fitted this one for me (for free as a consequence) have over torqued the ancillary components to such an extent, that I was unable to remove the coil housing and water rail, hence, I was unable to remove the thermostat.

I’m a reasonably experienced home mechanic, using good quality sockets and spanners. I had a good purchase on the bolts in question, but with muscle popping effort, in 3 out of 5 cases, the bolts ended up rounding off under the strain. Including the 8mm and another (10 or 13mm, I forget) on the coil housing, and one of the 10mm’s on the water rail.

Given that I was getting nowhere, I replaced it all and thought I’d seek advice before I broke anything terminally. So if anyone’s got any bright ideas as to how I can remove the stubborn and now damaged bolts, or bypass the problem, I’d be very grateful.

Cheers, Russ.

PS. Cheers Will & Dieter, the ratchet spanner was a must, I took out the thermostat bolts relatively easily, but the other stuff was a nightmare!

PPS. The thermostat appears to be stuck open as the car is warming up slower and is running cold.
Russ D Mellor

Russ,

I had something like this on the socket cap screw that holds the timing belt tensioner in place. The socket had been damaged and no matter what was tried it just damaged drive bits. Gave up in the end and went down the pub for the evening with the mate whose car it was. Next morning I got out the die grinder and carbide burr and removed the bolt head, the bolt thread then came straight out with my fingers. I had a spare bolt of the correct size and tensioner handy. If you don't have a die grinder then maybe a burr in an electric drill will do the same but more slowly. I don't know the parts but you may have better access than inside the tensioner on the front of the engine.
David Billington

well, the good news is that the bolts you are trying to remove have better positions than the ones that require the spanner.

Try hammering on a socket of the next imperial size down. the shocks from the hammer may free the bolts somewhat and the imperial socket will grip in a diffrent place to the metric.

Odd it sounds, but try tightening them slightly, when you feel them move try untightening then.

The thermostat is in a plastic hosuing pressed into the metal pipe you are trying to remove, this is only held in with frition and an O-ring, do you have any movement on the metal pipe that could free the position enough?

moving the metal pipe around may also free up the bolts.

finally (but probably firstly) did you give them a good soak with plusgas - it's penetrating oil on steroids and available at Halfords, just don't believe the claims about how long it takes to work, at the point patience will reward you, give a few blasts and peroids to soak (perhaps overnight) before trying the rounding process again!

Will Munns

Cheers guys,

Access is not brilliant, there could be some mileage in grinding out the 8mm head on the bottom of the coil bracket. We’d then just have 1 from 3 left and I may be able to spin and jiggle the bracket to break seal and hopefully loosen the 3rd bolt. I’m not sure if grinding on this one is too practical, and I don’t think I’d have too much thread showing in order to remove the stud. But I guess I could secure back with the two bolts and the remaining stub of stub?

With the coil bracket removed, access to the rail would be improved. Grinding the recalcitrant bolt head could then be an option, although given access I may have to invest in a die grinder instead of my trusty 4” angle grinder. I’ve just checked eBay and can get a 130W in a case with accessories and postage for £15, mental!

I agree with Will that the smaller socket option sometimes works and will try that and the plusgas (I was using GT85 but will invest) option before the grinder comes out. My suspicion is that they’ve gone too far for that. I had hours on them giving some serious s**t for no results

Any other thoughts would be welcome.

Thanks, Russ.

BTW: I did take all 3 thermostat bolts out just to see if the housing could be removed or wiggled, wishful thinking!
Russ D Mellor

Hi folks,

After some serious messing about, killing the stupid £15 die grinder I bought from eBay and having to cycle to B&Q for a decent one to finish the job. (eventually involved grinding the 8mm bolt head from the coil mount and a 10mm from the water rail), I removed and replaced the thermostat.

After putting it all back together I ran the vehicle up but noticed it was only heating up very slowly. It being dark and cold I left it until the drive to work this morning and confirmed the car was running very cold, taking an age to get onto the gauge and never did reach operating temp.

The old thermostat was seized solid, I checked the new up wasn’t (not in water, just manually), but I still have a problem with the car getting to temperature. I know it was cold this morning but previous experience suggests it should have warmed much quicker.

I have not fully bled the system, but don’t see this would make it run colder, so has anyone got any ideas why the car is still running cold even after a thermostat change and a 9 mile drive?

Cheers, Russ.
Russ D Mellor

Hi folks,

Has anyone got any ideas about this?

I guess the thermostat could have been faulty but the idea of taking it out again is not terribly appealing.

The car has struggled to get onto the 1st mark of temp gauge. Eventually some warm air comes from the heater, but it's not like normal.

I don't like using the car at the moment and am conscious of the fragility of the cooling system, so any help would be appreciated.

Thanks, Russ.
Russ D Mellor

It does sound like the thermostat still.

How do the pipes feel?
Will Munns

Cheers Will,

I'll check the pipes on the way home, do you mean the ones running from the rad in the front, or from somewhere in the engine bay?

I stopped after a couple of miles last night just to check nothing was too untoward (a lot of heat in the head etc) and it seemed ok, just cold. I could remove the expansion cap without steam and while there was some heat in the water in the tank, it was not that hot.

I'd gone over 5 miles before it crept onto the temp gauge and never actually heated to full temp which I guess is classic thermostat.

I replaced the thermostat the same way round as I took out the old one. But which way does the water flow and what are the symptoms if it's fitted the wrong way round?

I have a terrible feeling I'll be taking it out again this weekend, what a nightmare!

Thanks, Russ.
Russ D Mellor

if it were back to front I would expect it not to open rather than not to close.

You really ought to have bleed it properly, air in the system can lead to all sorts of odd behaviour.

The pipes to the rad - one will heat up before the gauge shows temp if the thermostat is jammed open.
Will Munns

hi mate,if your car is not reaching temp have you not put to much coolant in,try draining some coolant off and replace just with water.take expansion cap off then start engine.water should return back into tank to let you know that water pump is working.put cap back on.let idle with temp control set at hot(no fan motor running) and let air and water escape from radiator bleed screw.temp should be between 8 and 9 oclock when hot.you could try bleeding threw the main bleed screw next to the engine.if you take thermostat out ,boil your kettle,put water in a jug and put you thermostat in.if it opens then nowt is wrong with it,remember water boils at 100 and thermo will open before this.
ian armstrong

I reckon you've got air locks in the system, and if you have you are dicing with near-death by driving it. The chances of you cooking the head gasket are really high. Get it properly bled, soon.
Mike Howlett

Cheers guys, I appreciate the comments.

The pump is alright, it was replaced in my ownership of the car and when the engine is started with the cap off, you can see water pumping.

Too much coolant is also not a problem, but airlocks could be a contributing factor. I will properly bleed the system before attempting to remove the thermostat again.

To be honest it has all the classic symptoms of a thermostat not opening and I’m not confident that I won’t be removing it again. Which is rubbish as the job is really awkward.

Is there anything else, other than a faulty thermostat that would show the previously mentioned symptoms?

(Long time to warm up, 5 miles just to get on the gauge, never reaching operating temp, eventual heat from heater but delayed etc)

Yours in hope!

Russ.
Russ D Mellor

This thread was discussed between 05/11/2007 and 20/11/2007

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