Help!
GENERAL
Questions & suggestions
Q Some time ago at an airport lounge I bought one issue of Car Mechanics and was very impressed. Literally everything in it was of interest to me. I entered into a subscription and happy with that. Always looking forward to the next issue!
I’d like to suggest two areas which I would very much like to learn about from experienced mechanics...
How to get the brake disc loose from the hub if corrosion has bounded them together. Here in Norway with salt on the roads for half part of the year this might be a bigger problem than in the UK though and therefore not of interest for the majority of your audience?
I know that there are fancy tools (e.g. from Draper) for that but they are so pricey that they are not really an option for the infrequent use of the home mechanic. Maybe tools can be made with relative ease at home? I thought about this but was unable to come up with something.
How to best remove seized/corroded bolts/nuts (eg. suspension parts). How to determine if brute force, electrical/ pneumatic impact driver, heat, penetrating oil is best… and what if the bolt snaps?
If those have been covered in earlier issues of CM (before my subscription), maybe you could point me to those, I’d be happy to order if they are still available.
I’ve a minor suggestion for maintenance which might be of use for others...
You sometimes show the tasks of a typical maintenance for a certain car model. As part of that also the appliance of some oil to eg. door hinges, lock mechanisms was shown. I have found that chain lubrication spray intended for motorcycle chains (like this) is far superior to oil in such cases because:
► It is easy to apply as it comes with a long flexible spray tube
► It is very thin floating and penetrating when applied so that it gets to where it’s needed
► After the ‘thinner’ evaporates, it is not very sticky to be a lubricant so that dirt is not so easy collected
► It will not just disappear from rain or a car wash (after all it is made to remain on a fast-moving MC chain when driving in the rain for thousands of kms)
► It is compatible with rubber like in O-rings (as they are found in modern MC chains).
Jørg Gottwald (Norway)
A Presuming the brake discs are to be renewed, which they would normally be after removal, then tapping the inner flange of the brake disc firmly with a hammer to loosen any corrosion and then striking the face of the disc, will normally dislodge most stubborn discs. Applying a penetrating oil to the area between the disc and flange will also help in the removal.
It can sometimes be the case that the inner edge of the brake disc becomes so corroded that it will not easily pull past the hub flange. If this is the case the brake disc should not be re-used as it may become distorted in the removal process. This is applicable even if a puller has been used.
With this in mind it can be easier to remove a stubborn brake disc by grinding a small slot in the inner flange to both release the pressure on the disc and allow the penetrating fluid easier access to the inner area which will be the sticking point.
In my experience the most problematic brake discs for removal that I have come across were the early Ford Mondeo brake discs. I have had these break on removal due to extensive corrosion which did seem to occur internally between the brake disc and the flange.
In a similar way dealing with corroded bolts and nuts should always be dealt with on an individual basis. Each situation needs to be accessed, and whilst some bolts may succumb to a little heat, others will be in a position where heat cannot be applied due to the possible damage that may occur.
Brut force should never be considered unless, if the bolt were to shear, the problem could be circumvented by other means. So, if a sheared bolt then meant the bolt would need to be drilled this would become more problematic, but if as in some instances the sheared bolt would then allow the component to be removed without further incident, then this would be permissible.
Very often slicing a nut using a saw will allow its removal without damage to any connecting components, but the decision of how to tackle each problematic nut and bolt is one which is gained through years of experience which includes trial and error. Even then I am sure that many experienced mechanics will when met with such a problem be unsure of the best way to tackle it.
Induction tools are a good weapon in the removal of corroded nuts and bolts, but they are not infallible and expensive.
GENERAL
DTI gauge & stand
Q Please could you recommend a dial test indicator and holder/stand for checking the brake disc run-out on a BMW E36 325i?
Greg Fox
A There are a wide range of DTi gauges available and some are quite expensive. The tolerances needed to check the disc run-out can be checked without spending too much money. The gauges at this site start at under £20 https://bit.ly/CM3yDTI and this is perfectly good for the task. A full kit with the stand is also available at the same source for £83.98 and will cover all needs. The main problem is supporting the DTi gauge and keeping it steady whilst carry out the check.
A very good magnetic stand is available separately from this company https://bit.ly/CMESDTi for under £18. The company can also supply Dial test indicators, but these are in the higher price bracket, and I think such precision is not required.
AUSTIN ALLEGRO
Intermittent starting problems
Q I’ve intermittent starting problems on my 1982 Austin Allegro 1.3HL which has covered only 74,000 miles. I got the Austin last year and was told it had issues, seemingly with the battery draining. I fitted a new one, a new earth strap, even removed the boot light, just in case.
The symptoms persisted, it might start fine or give symptoms of a dying battery so over the course of the year I have replaced the old distributor with an electronic one, new coil, leads, plugs, solenoid, a known to be working starter, a tune-up and timing check. Compression test which was spot-on but still it happens, usually when somebody is watching and so playing-up to the marques unwarranted reputation.
Today for example, I tried to start outside the garage - dying battery symptoms - connected the charger and it showed full battery, turned the key and it fired up perfectly! Generally it makes no difference if I’ve gone 1 mile or 30 miles, next turn of the key is always a leap of faith.
