Misfiring and Belt Screatching. - MG-Rover.org Forums
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post #1 of 4 (permalink) Old 07-04-2017, 17:24 Thread Starter
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Misfiring and Belt Screatching.

Since having my water pump changed on my 2003 ZR, on cold start up there's a screatching coming from the engine (timing belt was changed same time as water pump) and the engine misfires causing EML to come on.
After reving the engine for a few seconds the sound disappears and the misfiring subsides along with the EML light going off, however is still slightly present on idling.
The engine has lost engine coolant over the last 5 weeks (completely emptied) but cannot see any leaks. Head gasket was sniff tested and was fine.
Any help or suggestions would be appreciated.
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post #2 of 4 (permalink) Old 07-04-2017, 18:55
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I'd check if the timing belt's timed right. Also, the belt too tight causes them to screech, so check tension and loosen within the allowable tollerance. Park on cardboard to spot the leak. If there is no external leak, chances are it's the IMG which aren't too hard to change. If a garage did the job originally, take it back and get them to redo!

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post #3 of 4 (permalink) Old 07-04-2017, 18:59
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Most of the time a sniff test will not detect gasket failure on a K series. A sniff test detects combustion gases. A K series gasket failure is invariably a failure of the elastomer sealing bead and not the fire rings, So a sniff test will tell you nothing.
The screeching is probably the alternator drive belt.
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post #4 of 4 (permalink) Old 07-04-2017, 20:51
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The K series head gasket can fail either by way of the elastomer beading degrading (due to excessive heat) or by failure around the fire rings (which is quite common). In the case of the latter, exhaust gases will be forced into the coolant system, so yes, a sniff test will verify if there is failure of one or more of the fire rings. A sniff test will only act as confirmation a failure by revealing excessive levels of hydrocarbons in the coolant; it won't confirm that the gasket is sound because there are always some traces of hydrocarbons in the coolant, and these will be detected. It won't tell you if the elastomer bead has failed - If the head gasket has failed and you are loosing the quantity of coolant you state (and you say there are no signs of external leakage), there will be signs of condensation or emulsified oil on the dipstick or within the oil filler cap.

There are several explanations for coolant loss - simple leaks in the system pipework, radiator or heater matrix; failed seal or pressure valve in the expansion tank cap; leaking water pump; or inlet manifold gasket failure, as well as head gasket failure.

If the IMG has failed, there is often a misfire for a short time after first start up.
I would say your squealing belt is very likely to be the alternator belt insufficiently tightened.
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