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post #2 of (permalink) Old 22-03-2004, 09:08
Scarlet Fever
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Join Date: Jul 2002
Location: Near Stansted Airport
Car: MGF
Posts: 5,476
Blog Entries: 9
Depends on how it goes.

If it goes slowly then the clues are as follows:

Coolant level drop
'mayonnaise' in the coolant and / or oil

Mayo is the slang term for the 'coffee and cream' coloured emulsion formed when the oil and coolant mix. This is the sure sign to the layman that HGF has occurred. In this case, ring a garage and have the car towed in - do not drive it. The garage can confirm HGF in a number of ways, pressure testing the cooling system for leaks, visual inspection of the gasket externally, using an MOT exhaust 'sniffer' in the expansion tank to check for hydrocarbons.

If it goes suddenly then the clues are as follows:

A large cloud of white steam behind you (from the expansion tank).

This often goes unnoticed by the driver because of the expansion tank's location in an F, i.e. right behind the driver. Also, it is unlikely to be noticed if it happens after dark for instance. If it happens stop the car asap and call for recovery. Wait for the engine to cool down and then check for 'mayo' (be careful, do not open the expansion tank while the engine is hot - risk of scalding).

If you carry on driving, the engine will run out of coolant very quickly (the K-series is a small coolant capacity engine), the temperature guage is extremely damped and unfortunately by the time it starts registering hot you will have lost too much coolant already and cooked the engine = s Coolant temperature guage is therefore practically useless in this regard do not rely on it.

Straight HGF replacement (using uprated gasket and steel dowells) is around the 500.00 mark (mostly labour). Any additional works is obviously extra, additional works will depend on how early the symptoms were spotted and the car switched off, normally if you spot the steam and switch off pretty quickly (i.e. pull over straight away and switch off) you should get away with a straight gasket replacement. If the engine is allowed to run with little or no coolant the costs can spiral.

Also, HGF is the end link in a chain of failures, the gasket doesn't 'just go', normally there is a failing elsewhere that has lead to the HGF. When the gasket replacement is being done it is important to find the cause and rectify it.

Some examples of causes are:

Loss of coolant caused by:

1 ) Corroded radiator (typically around 5 years, age / wear and tear issue)
2 ) Split hose (age / wear and tear issue)
3 ) Failed hose clip (age / wear and tear issue)
4 ) Corroded underbody coolant pipes (also circa the 5 year mark age / wear and tear issue)

Loss of coolant pressure (it's a pressurised system) / air bubbles in the coolant caused by:

1 ) Failed valve in the expansion tank cap (age / wear and tear issue)
2 ) Broken radiator bleed screw (dealership issue)
3 ) Poor coolant change (dealership issue)

Electrolytic corrosion of the gasket caused by the inhibitors in the coolant breaking down:

1 ) Coolant 'top up' rather than replacement (dealership issue)
2 ) Missed coolant change (dealership / owner issue)

Excessive thermal expansion / contraction leading to bead movement / separation, caused by:

1 ) Plastic dowells (MGR issue - solved by steel dowells)
2 ) Old style (bonded bead) gasket (MGR issue - solved by uprated gasket)
3 ) Poorly sited thermostat (MGR issue - solved in the TF)


So you see, HGF is not a simple open and shut case, there are a myriad of potential causes and MGR have made great strides towards solving some of them, but as the cars get older the risks increase and also muppet dealerships don't help - they are normally on a tight time schedule to complete servicing works and therefore the temptation to simply top up the coolant rather than replace and bleed properly is there. Also they have a vested interest as any HGF works are likely to be done at a dealership (due to the warrantee). Not that i'm saying they cause HGF you understand, but there is a conflict of interest here.

All you can do is be vigilant and if it happens make sure the cause is found and dealt with and the new gasket is the uprated version with steel dowells. You can also take out an aftermarket warrantee (if it has expired), the AA do one for 55.00 p.a. that covers up to 500.00 in payments - this will pay for a 'normal' HGF. The other alternative is to squirrel away some cash over a time period into a high interest account - it is pretty painless to do and if you need it the money is there earning interest for you.

Last edited by Scarlet Fever; 22-03-2004 at 09:13.
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