MGF COOLANT PIPES KNOCKING? HEATING UP?

[tahitiblue1999]

Hi...I have a 1999 MGF that I have had for 2 years. In the last 6-7 weeks it has developed a knocking sound that seems to come from underneath the centre of the car and sounds like radiator pipes contracting and making a noise. It starts after approx 10 mins of driving in traffic and there are approx 6-7 knocking sounds about 5-10 seconds apart which last for a couple of mins then stop. I have opened up all the coolant bleed points and tried to get out any air locks, I have checked the dipstick and filler cap and see no signs of mayo. I have been to my local garage and they looked at it but just looked blank at me...and said they found nothing....I felt the pipes after driving and the passenger side is hot and the drivers side warm, I looked in the header tank and the coolant looks clean and is running back in to the tank ok...I really need some expert advise, cthis happens evry time I drive anywhere, could it be the thermostat or temp sensor? When I bought it the coolant pipes underneath were replaced but I have no idea if it has ever had the HG done? It has 71'000 miles. Can anyone help?? All my local garages dont seem to have a clue!!!

[Charless]

Could be something to do with the pipes that feed the heater matrix - these are in the 'transmission tunnel' and would be more audible inside the car. They are also fixed relative to each other by brackets along their length like the underfloor coolant pipes and a closing plate at the rear. I am wondering if; like with domestic heating systems, the clunks come from differential expansion rates of metal no longer quite so attached as it once was. If it isn't losing coolant or overheating and you describe the radiator as working and it has survived 6 weeks like this; I would try not to worry about it.
How easy that is to say when it isn't my car!

[Mike1]

Mine has done the same thing for the last two years so I doubt it is anything to worry about. After driving about a mile from cold it starts to make a "ting" sound every few seconds. Only lasts about half a minute so doesn't bother me. I also assumed it was the under floor pipes and actually find it quite reassuring knowing that the water is circulating.

[Bandit]

... and actually find it quite reassuring knowing that the water is circulating.

I had an F from new that would emit a loud clunk from the underbody pipes after a few minutes of running, when I part exchanged it for a Trophy 160 I almost found myself missing it...

Perhaps worth raising the car and loosening the bolts holding the underbody pipes, running the engine up to temperature until the noises occur, then tightening the bolts again.

[Mike1]

Just warmed mine up while parked. Noise definately coming from under the car rather than inside the tunnel. Will probably fit new pipes soon anyway, I repaired them about 5 years ago and am surprised they have lasted this long.

[tahitiblue1999]

I have just changed the brown temperature sensor just in case seeing as its only a cheap part, but its still the same, does that control the front fan? Im not sure how often the front fan should come on? When I opened the rear panel what struck me is how hot the pipes and engine seemed to be, is this normail? I left it ticking over and the temp guages raised to normal levels but still this annoying ping from underneath, I cant tell where abouts its coming from, it may even be coming from 2 places...also on some occasions if only a short journey (15mins) I dont get any knocking...If anyone can give any advise please post a comment....thanks.

[Rob Bell]

MEMS - the engine management system - controls the operation of the front radiator fan. The temperature sensor that it uses is the one you've just replaced, the brown one, part# GTR206.

How often should it come on? That really depends - and therefore something of a "how long is a piece of string" question unfortunately, but clearly, if the engine coolant temperature starts to go up, the fan should come on.

I guess you're question is "is my radiator fan working?" - and the answer to that is quite easy. Disconnect the water temperature sensor (brown) and the fan should instantly come on. If it doesn't, then there are typically two failure modes:
1. blown fan fuse - either fuse 6 in the under-bonnet fuse box, or fuse 15 in the cabin fuse box.
2. seized/failed fan motor - seizure not uncommon over the winter months, where the fan is rarely called upon, and is usually exposed to road grime and salt.

A fan can be recovered using liberal quantities of WD40 and some brute force and ignorance, but second hand replacements can be had for reasonable money.

More here

HTH

[tahitiblue1999]

The thing is the temp guage never goes past half way after warming up and the oil temp guage stays normal too, if the radiator or rad fan was no good wouldnt the temp go up and car over heat? I had the gearbox cables done about 3 months could it be related to that at all? Could it be the metal coolant pipes underneath are bolted on too tight not allowing for any expansion?

[tahitiblue1999]

Also the fuses are all good....

[Charless]

The gear cables also go through the same closing plate that the heater matrix pipes do, so the noises might very well be connected with that work. There doesn't sound to be a problem with the cooling system function, so I wouldn't risk replacing bits without a good reason.
I have two 14-year-old Fs with full original hose sets and only replaced the original radiators on both this year for leakage failure, not cooling failure.

[Rob Bell]

There probably is no problem with the radiator or its fan, but the fact that the car doesn't appear to over heat can on occasion be misleading. The gauge is purposefully insensitive - and will stay in the mid-portion of the gauge until the engine really does get seriously hot! Also, if the ambient temperatures are reasonably low, and especially if the car is moving and not stationary for a long time, the radiator fan isn't required to dissipate the heat. The fan only really comes into its own when stuck in very slow moving or stationary traffic - and even then, from cold, it'll take the best part of 3/4 of an hour before the temperature needle heads north of the usual 'comfort zone'.

[tahitiblue1999]

So perhaps just turn the radio up so I cant hear the knocking? Just annoying and worried its causing damage...

[mgtfnut]

After all this excellent advice, why don't you jack it up, support it well, and start up from cold and see/listen what happens

Have a socket ready to slacken off the underfloor cooling pipes clamp fixing (careful, they might be partially seized/rusted up) and copper grease the points of contact. It doesn't hurt to get underneath and have a look from time to time. There's only so much interwebby advice can do, you can't beat a bit of hands on investigation

[redbeard57]

If you are in the area, why not come down to the Helsby Arms (WA6 0JE) on Thursday (27th) for the monthly area meeting, where somebody may be able to suggest a solution to your problem.