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MG ZT, Rover 25
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Discussion Starter · #1 · (Edited)
BACKGROUND

The Rover 214 was suffering coolant loss at the rate of 300 ml in 300 miles. There were no visible external leaks. I thought that the quickest solution would be to put it into a local garage for repair. When I did so, unsurprisingly, they diagnosed Head Gasket Failure (HGF) and set about a seemingly comprehensive repair i.e. skimmed head, new gasket, bolts, thermostat, water pump and cam-belt kit. However, the repair failed and when I asked them to do it again as they had agreed a 12 month warranty on the work, they claimed that the coolant loss into the oils was due to cracked/ unsealed liners and recommended a replacement engine. I considered scrapping the car, but eventually decided to have a look at it myself; paying the garage to release the car and towing it home.

The car was originally driven to the garage with normal black oil in the sump and consuming a little coolant, when it was returned the oil was the classic emulsified ‘milkshake’ of severe HGF and a non-runner.


REPAIR

Delayed by the ice and snow I eventually got around to looking at the engine. I removed the spark plugs and noted that all cylinders had ‘chocolate milkshake’ (emulsified oil) swilling around in them.

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P1. 'Milkshake' in cylinders

This gave me some doubt that it was a liner problem, as the garage had indicated, as if it was I would expect the mess to be in only the damaged cylinder(s). However, it was possible that they all had been damaged if the engine was turned over with the head off. Next I established that the engine could turn over (with spark plugs removed) – it did. I drained out the oil; about twice the amount you would normally expect came out which was severely emulsified. Then I drained the coolant – this was clean but barely a litre came out.

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P2. Emulsified Oil


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P3. Small amount of coolant

I stripped the engine to investigate further, supported by a Haynes manual and a number of useful threads from this web-site (as the procedure of a HG replacement is well recorded in these sources, I will not go into detail). The milkshake and the mess seemed to have got everywhere: cylinders, inlet manifold, exhaust manifold, air box, cams and everywhere the oil would normally flow. I removed the head and cleaned everything up the best I could using rags, water, detergent and elbow grease.


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P4. Removing the Cam-belt…



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P5. And under the rocker cover…

I noted the following points of interest/ possible issues during the strip:
a) One of the two exhaust manifold supporting bolts was missing.
b) Plastic dowels were fitted between the head and block (steel dowels were supplied in my gasket set).
c) There was no metal shim fitted between the MLS gasket and head (such as I have seen supplied with other MLS gaskets).

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P6. Mess in all the cylinders. Note plastic dowel on rhs – lhs dowel came out on removal of the head. Also note no head shim fitted on top of gasket.

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P7. Cleaning the head

Once the engine was cleaned up I inspected the liners the best I could with the head off and pistons level in the safe position. I could detect no movement trying to waggle them with gentle pressure. The top of liners to block measurement was just under 3 thou with it being slightly lower still on cylinder 1. The block and head surface looked flat and in good condition with no obvious patches of porosity.

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P8. Inspecting the liners

I needed to decide whether to repair this engine – 50k, f.s.h., g.c. – or fit another one bought from a scrappy or ebay. Although the liner heights were not ideal on my engine they were better than another K series I had recently looked at, and more often than not you would not get a detailed inspection when buying a used engine. Further, I had not seen a 1.4 engine with such a low mileage. I was not certain of the condition of the lower part of the liners or their seal, but the evidence did not really indicate a problem there. Thus I decided to replace the HG on the current engine without deeper investigation.

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P9. New HG provided with head shim and metal dowels (out of picture)

I replaced the HG with an MLS type with head shim and steel dowels, and reassembled the top end of the engine and flushed and in the oil and water. After a bit of fiddling about I got it running okay with no visible leaks and drop in coolant level. The exhaust was smokey, but I put this down to burning off the milkshake in places I hadn’t been able to remove manually. I took it for a test drive, stopping every mile to check for leaks. On my third stop, I lifted the bonnet and my heart sank – the coolant level had fallen and steam swirled around the back of the engine. Looking at the rear of the engine, it did not take me long to see the cause of the problem – coolant spurted out of the thermostat to coolant rail joint.

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P10. Leak between thermostat housing and coolant rail

After I got the car home, I removed the 2 bolts on the coolant rail (not as easy as it sounds as there is very limited access), pulled it away from the thermostat and removed the O ring. The O ring was in poor condition, and possibly was not seated properly when the thermostat was replaced as part of the original repair. I replaced the O ring and reassembled the piping. Again, I static and then road tested the car – this time no problems and the excessive smoke had cleared by about 50 miles. I’m now on 500 miles since the repair and it's running well.


CONCLUSION

As my HG repair seems to have cleared the problem the liners must be okay and the garage fitted HG must have failed soon after fitting. On dismantling, I noted that the head shim was omitted, plastic dowels were used and a manifold support bolt was missing – these could have been contributory. Further, if not closely monitored on the test run, the significant leak in the coolant rail to thermostat joint (which was only apparent when the engine was fully up to temperature) may have let sufficient coolant to leak out of the engine to cause the secondary failure of the head gasket.
 

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mg_zr
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No replies to this excellent write up? I wish I had half your car repair knowledge. Seems like your wasting your time putting your car into the local grease monkeys!
 

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MG ZT, Rover 25
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Discussion Starter · #3 ·
No replies to this excellent write up? I wish I had half your car repair knowledge. Seems like your wasting your time putting your car into the local grease monkeys!
Thanks - I think no replies is partly my fault as I stuck it in the wrong area when I first posted it and one of the moderators moved it here.

TBH I still use garages for difficult stuff or if I'm too busy, but consider more carefully whether to do it myself/ who to get to do it.
 
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