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Old 6th July 2018, 19:30   #1
Sonic ZS
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Default 1.8 K-Series Headgasket Choice - Advice Please.

I have recently become involved with sorting an overheating problem on a 1.8VVC MG TF, and I'm hoping some of the forum gurus could point me in the right direction (as my knowledge of this problem is minimal).

The car will drive for approx 10 mins or idle for about 20 mins without any real problem, then the coolant in the header tank slowly starts to rise (over maybe 5 mins, pulsating up & down slightly in the process), but eventually filling the bottle right to the top. Finally, the system starts to emit quite violent blasts of air/coolant into the header tank (which can be clearly seen next to the cap, every few seconds), much like a small volcano. At this point, a temp reading on the head outlet shows around 110-115'C.

Now, not wishing to automatically assume it's a 'K-series...it'll be the head gasket' , I have:

Fitted a new coolant cap.
Fitted a new 88'C thermostat.
Removed and flushed the radiator (in both directions), flow seems decent.
Blown through the radiator fins with an airline to clear out any muck.
Flushed the cooling system from front to rear, all seems good.
Bled the radiator, heater matrix and engine bleed points.
Taken temp readings around the system from cold, to check for correct flow as the engine warms up.
Checked that the heater is working - all ok.
Checked both the rad fan and engine bay fan - both working.
Plugged diagnostics in to ensure the ECU is seeing sensible figures from the new temp sender - all ok , fan on at 105'C, off around 96'C, all tested and working.

Now after doing all this, there wasn't much else in the system to suspect than the head gasket, so took it off yesterday. The previous owner had said he'd recently done the gasket - he'd had it skimmed and fitted an MLS along with a head saver shim.

However, on disassembly, the shim just fell away from the head - shouldn't it have been bonded on with a product such as Wellseal or similar ?

Secondly, a quick check today appears to show the liners are sitting about 1-1.5 thou proud of the block. Is this acceptable for an MLS gasket ? I was under the impression they should be 3 thou proud or more - would this make a difference ?

Everything else appears to look pretty good (although closer inspection tomorrow), but based on all the above, which gasket do you think I should use ? And is the N-series kit (with revised oil rail & stronger bolts) worth the extra ?

Car has done approx 60K.

Please let me know your experiences and anything else I may have missed - many thanks in advance !
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Old 6th July 2018, 19:33   #2
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Running it with the expansion cap off is meaningless, as it is a pressurised system.


Hardly surprising that the coolant starts to boil with no pressure to stop it.
How does it do with the cap on?
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Old 6th July 2018, 19:34   #3
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Payen 750 elastomer gasket for me Paul
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Old 6th July 2018, 20:14   #4
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Quote:
Originally Posted by mbonwick View Post
Running it with the expansion cap off is meaningless, as it is a pressurised system.


Hardly surprising that the coolant starts to boil with no pressure to stop it.
How does it do with the cap on?
Sorry, but not sure why you think the cap was off ? All of the observations noted were with the new cap securely in place ! : The volcano effect can be seen through the translucent plastic of the header tank.
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Old 6th July 2018, 20:26   #5
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https://www.dmgrs.co.uk/collections/...v-to-zua000530
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Old 6th July 2018, 21:13   #6
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Quote:
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Thanks Les, I've had a good read through the DMGRS site (and received excellent service from Matt previously), but ideally want to hear advice from people that have actual experience in these matters
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Old 6th July 2018, 21:16   #7
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Quote:
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Payen 750 elastomer gasket for me Paul
Im with Ronnie on this one, fit the elastomer gasket.
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Old 7th July 2018, 06:03   #8
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The MLS head saver shim should be loose not bonded on, I’ve seen a lot of MLS gaskets that are poor quality so I only use the elastomer Payen 750, even if the liner heights are within spec for MLS use
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Old 7th July 2018, 07:52   #9
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Prep is the most important part , best quality gasket badly thrown together will not last.

Generally advise the Payen BW750 now as it's more "forgiving", although I have used ebay MLS gaskets from reputable sellers without fault.
Often they're BGA brand. My current ebay one has lasted me a drive from Manchester to Germany and back, 7 laps of the 'ring, 1 hour of the GP circuit, a track day at Cadwell, a track day at Angelsy , 2 hours on at Donnington, plus a good few thousand miles of general driving. Again prep is key.

For headbolts you really want to avoid unbranded. Seen one snap when the guy I was helping didn't listen and went for cheapest on ebay. I have reused after checking to the allowed tolerances, but now use Kamax bolts as it was £30 for a set I think
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Old 8th July 2018, 17:02   #10
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Thanks for the replies, gents Have carefully cleaned up both the head and block this weekend, results as follows:

Liner height protrusion above block, varied from 1 to 2 thou. max.
Liner to liner variation, almost all level, at worst maybe half a thou.
Variation across head, at most half a thou.

There are no score marks or damage to either face.

Could the albeit slight lack of required liner protrusion for an MLS gasket caused the previously mentioned overheating & bubbles ?

Many thanks
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