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MG MGF Technical - Stainless Underbody Pipes

I wonder if stainless pipes radiate heat more efficiently than the original steel?

After changing to stainless today my temp gauge seem slightly cooler. Perhaps it's wishful thinking!

Last year I flushed the system thoroughly and renewed the coolant with pink OAT. Temp gauge was a tad under half way before OAT, and nearly a notch below after. With stainless I am ever so slightly lower still. I have observed the proper air bleed procedure each time.

Replacing the pipes was not particularly difficult. I had the car up on wheel ramps at the rear, with the front tyres running over stout planks to gain height. Trolley jack can then be put under the front jacking point followed by Axle stands under the subframe to get the car level. Decent access is now possible, despite my middle aged spread. Underbelly plate has 22x10mm screws all of which came out first time. The pipes are held in by three longer 10mm screws, the front one was seized. PlusGas and a belting freed it off. The underbelly pan is badly dented (speed humps maybe) so I expect to be taking those 22 screws out again as and when I locate a better one. In anticipation of that time I've cleaned all the threads with tap+die and copper greased the lot. Reserve about 3 hours to do the job.


Jeff
J Lennon

I think they do, they seem thinner and may well have a smoother inner bore than what they replace, allowing more/faster flow through the radiator. I shouldn't worry about the plate...
Charless

Thanks Charless for your point of view. Maybe it is a better flow rate that gives lower temp gauge reading. Here's my observations over the last 5 months.

Before the winter set in decided to replace the coolant with OAT mix, given the low potency of the existing mixture, contents and type unknown. After draining I reverse flushed with an adapted garden hose jammed into the radiator bleed point - exiting at the bleed points and expansion tank. After the shock of seeing lots of much muck, I continued this until all ran clear. Then ran the motor on clean water until warm and drained off, replacing with OAT once cold. Did the air bleed procedure and repeated this after a couple of journeys. Very pleased with a lower temp gauge reading.

During the winter with infrequent and low mileage trips, mayo on the dipstick was evident. I put this down to condensation. Once the mayo was cleaned off (2 or 3 wipes) the engine oil was clean. The coolant was very very slightly discoloured with perhaps residual sludge that OAT may have taken off the internals. However the coolant required a slight top up every three weeks. I've been concerned about impending HGF ever since mayo.

At the MOT in late Feb I was allowed a viewing "underneath" and saw the steel cooling pipes were on their way out with lots of rust bubbling through the paint and evidence of a slight weep at one of the bracket welds. And that's why the new s/s pipes have been fitted. Probing the old pipes with a screwdriver hasn't encouraged a gaping hole anyplace. They were a little furry inside which may explain the ever so slight discolouration of the pink OAT. I mean it looks pink when it's poured, but on leaving to settle in a glass jar, some deposits fall to the bottom - similar to the sediment in a bottle of vintage wine. I captured the OAT drained out during the pipe change and let it settle - decanting just the top 3/4's for re-use.

Now I must "wait and see" if the new pipes cure drip loss of coolant and if the mayo disappears with warmer days and longer more frequent trips.

Jeff
J Lennon

Just my 2p worth. I had one of the first Mike Satur s/s pipe sets. Although one of the pipes needed heating and "re-orienteering" they have been fine. Running temperatures are definitely cooler, and heat transfer seems more effective. I have a Scangauge to measure cylinder head temperature out, and a another coolant gauge replacing the clock reading return coolant temperature from a fitting silver soldered onto the metal water pump return pipe. I've got a PRT under the washer bottle, and can read temperature gradients in different ambient temperatures between coolant going out of the head and going back into the block. The s/s steel pipes seem to give a +/- 10*C difference in winter, and less in warmer times.

Sealing with pink OAT is a nightmare. It is far more searching that older glycol coolants for some reason.
Jerry Herbert

1996 VVC.
Prior to the holiday weekend I fitted the new s/s pipes, bled the system free of air and rechecked it a couple of days later. No air.

Now, after a weekend of various jaunt's, including a 100m trip to Devon and return I am pleased to see no change in coolant level (OAT) and no mayo on the dipstick, just nice clean Magnatec per the recent oil change. Happy days! During these journeys the temp gauge has been nicely under half way at all times. Oil temp varies in line with right foot, never more than a tad over the first notch off the stop.

Previous slight loss of coolant must have been a rusty underfloor pipe and slight dipstick chamber mayo probably caused by condensation. I've noticed the yellow end of the dipstick has an "O" ring which looks hard and cracked. Maybe this has been letting in damp air, although I would have thought positive crankcase pressure should prevent this and the seal is to keep oil in?

Note to self... replace the dipstick "O" ring.

If I could remedy that top end rattle I'd be a happy chappy - it's only there when the engine is hot. VVC mech's or what else?

Jeff
J Lennon

The thermal conductivity of stainless steel is different to that of mild - but the coolant temperature is dictated by the operation of the thermostat. Therefore, if there is a cooler temperature being recorded, it suggests that the thermostat isn't closing properly...
Rob Bell

Got say that I've had stainless steel pipes fitted for a couple of years now and I haven't noticed any difference in the running temperature of the car.
David Clelland

A pipe that is to quote Jeff "a little furry inside" will flow much slower than a new, smooth pipe, so I suspect if there is a difference it's due to quicker throughput of the coolant.
bandit

Thanks to all for your comments which, with my own observations, convince me the slightly lower temp is down to the combination of better flow with clean pipes and that s/s without paint conducts heat more efficiently than rusty m/s with flaking paint.

Rob's thought's about the 'stat are potentially valid - I've no idea about the state of it. I'm kicking myself I did not inspect it whilst having the cooling system drained! AFAIK it could be a wrong temp unit or been modded with 3mm hole. However, the engine warms up quickly and the temp gauge remains constant regardless of driving conditions, so it may be standard and working OK. Should I adopt the attitude of "it's not broke so don't fix it", get on the case and change it for peace of mind or consider altering the stat position. I've read it may pay to put the stat close to the radiator in a bypass circuit?

Jeff
J Lennon

There's quite a lot of discussion on the merits of relocating the thermostat (the "remote thermostat"), both on this site and on many others (particularly the Lotus forums - see the affiliated BBS here, and the SELOC forum). In fact, it is such a good idea, MG Rover did the same thing themselves, with the additional modification that their system also opens under pressure - the Pressure Relief Thermostat (PRT).

I think that this is a modification that is certainly worth considering - and should help damp the thermal cycling that many have proposed as one of the causes of HGF on MGFs. I think that you may have found Jerry's thermostat modification where it has been inserted into the coolant hoses at the front of the car? Should work a treat... :o)

Regarding a lower running temperature with the s/s pipes - I agree you'll get more heat loss from them, and the flow may be better, but it is the thermostat's job to regulated temperature, so if the temperature is measurably lower, then the thermostat can't be closing as it should be - as it should maintain a set temperature what ever cooling system is attached to it (within reason of course!)
Rob Bell

Jeff,
If the car warms up quickly then you haven't got the 3mm hole drilled in the existing thermostat. All reports I have read about this now out-of-favour mod, are that it takes forever to warm up either the gauge or the cabin heater!
Charless

This thread was discussed between 27/03/2010 and 13/04/2010

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