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MG MGB Technical - What kind of soap...

Had a squeal that I thought was a fan belt...changed the fan belt and it is much better but not gone...maybe don't have the belt tight enough...went into the archives and found a thread that said to put soap on the fan belt...my question...bar soap..liquid soap...what kind of soap?
Bob Dougherty

A load squeal is usually the belt slipping, in which case any lubricant is only likely to make it slip without squealing, and easier! A rhythmic slight squealing could be a bent or misaligned pulley - had that on the V8. It was the alternator not in line, a couple of washers under the mounting brackets sorted that.

For years I've checked my belt tension by seeing how far the middle of the longest run can be deflected from its 'at rest' position to or from the other side of the loop with light-ish finger pressure, and set it to about 1/4"-1/2". I've never had belt squealing in 40 years, and only had to replace a water pump once each on two cars quite soon after coming to me after many miles with other owners. Some manufacturers are a little more precise and state a deflection with a particular force, and others require two marks to be made on the belt a certain distance with no tension, and the alternator adjusted to cause those marks to move apart to another certain distance, i.e. the belt is stretched in use. The Leyland Workshop Manual in the Cooling section states for both dynamo and alternator systems it should be possible to move the belt laterally in the middle of its longest run by no less than one inch! Is that in one direction which seems a helluva lot? Or a total in both directions i.e. 1/2" each way which seems more reasonable? The Electrical section just says to "remove any undue slackness". Haynes in its cooling section says there should be a sideways deflection in the middle of the longest run of 1/2" on 'early' models, and 1/4" under an applied load of 7.5 to 8.2 lbf. Both 'lateral' and 'sideways' imply to me to be pushing or pulling it towards the front or rear of the car, and not towards or away from the other side of the loop which is always the way I have done it. Also is it in one direction or both? It seems likely that when using a spring-balace to apply the stated force for later models it would be in one direction only. The distance for that is half that for 'early' models, so do the early ones have twice the play? Or is theirs in terms of total deflection in both directions? And for that matter what is the definition of 'early' and 'late'? (Dynamo vs Alternator?). FWIW my 1967 Mini Workshop Manual also quotes an inch in the longest run, but an 80s Metro Manual quotes a much smaller deflection of 3/16" and in the shortest run. It also shows it being pressed down towards the crank pulley i.e. not sideways, and only in one direction from rest. Interestingly it also quotes a torque wrench value of 11 to 11.5 lbf when applied to the alternator pulley nut to produce slip, which is perhaps the most useful and relevant approach.

The Lucas Fault Diagnosis Manual has a drawing, which is repeated with the same deflection distance for dynamos and alternators, and shows 1/2" to 3/4" (13-19mm) in one direction, and towards the opposite side of the loop.
PaulH Solihull

Bob--use Ivory bar soap. Works for me. Just hold the bar against the belt for a few seconds while the engine is running.
JM Morris

Good research Paul! I guess some soap over the non-friction side of the belt, ie the top might just lubricate and feed this often dry side of the belt and where its edges would touch the pulleys it might stop a squeak? Mike
J.M. Doust

While we are on this subject; Smoe modern belts are of course 'serpentine' not that this applies to the MG with a standard 1800 unit, but I was thinking of belts which seem to have 'teeth' on the inside or friction surface. Mine is like this, and while I have never experienced slip and or sqealing, do these belts grip better? Certainly the supercharger kit from Moss comes with a sort of mini serpentine belt. Mike
J.M. Doust

Bob,
Paul's advice aside, a candle works too - all same sash windows and skiis.
R
R Walker

I think the toothed belts are more to do with resisting cracking on the back from being bent round a small pulley. The teeth actually reduce the surface area of the V of the belt, but when bent around a pulley the teeth move closer together, which reduces the gaps between them, so the grip ends up being almost as much as originally but with longer life.
PaulH Solihull

Hold the bar soap on the CONTACT side of the belt. Under heat and pressure, the bar soap coating becomes ever so slightly tacky, thereby eliminating slippage.
JM Morris

This thread was discussed between 13/10/2011 and 19/10/2011

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