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mg_tf
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Cheers Rob I'll not worry too much yet. I let it run for ten mins or so this morning while checking the main pipes to the radiator but neither even started to warm up (anyone know how long this should take?). Radiator and coolant rail bleeds fine but nothing from the heater bleed, no hissing or coolant, nothing!

Also, where the coolant enters the header tank there's just a small dribble, no strong flow like I'd expect to see.

Are there any valves etc which could be knackered and causing this? (It's got a PRT btw) cheers.
 

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'06 ZR +120 (HQM) '04 ZR 105 (IAB)
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There shouldn't be constant flow into the expansion tank - it is there to accomodate expansion as the coolant warms up and expands, but it isn't part of the coolant circuit. The small pipe that comes from the top of the radiator and the inlet manifold is a bleed pipe. You might get some flow through it as the air bleeds out of the radiator and cylinder head, and there may be some flow through it at higher engine revs, but constant flow of coolant through it at idle/lower engine revs would suggest a problem.

Did you take these pipes off and flushe them through? Emulsified oil gets into here when you have a serious HGF, but often doesn't flush out during a normal flush.

It is normal to fill the sump with cheap oil and the coolant system with plain water containing a flushing agent to clean out the emulsified oil/water mix from all the narrow passageways and nooks and crannies in the engine. Then after a few days usage, drain the sump and coolant system and change the oil filter again and refill with fresh good oil and new coolant water mix. There still may be emulsion continue to work its way out of the syatem for some time to come, so you just need to keep cleaning the expansion tank out periodically until it stops.
 

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mg_tf
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Well I'm relieved about the flow into the header tank now thanks! I never cleared the hoses out properly because I caught the hgf as soon as the first signs appeared so didn't think I needed to. I like the idea of sticking a dishwasher tab into it so I'll try that!

I'm just concerned about coolant not flowing properly and waiting so long for the radiator pipes to heat up that the engine overheats! I suppose I'll just leave it running and watch the temp dial like a hawk.

Cheers for your comments guys!
 

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rover_400_95_99
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Overheated

My 1999 K series Rover got hot quick so I stopped and on inspection radiator overflow bottle is a oil mayo mixture, and all additional engine oil added to motor seems to also go to the overflow bottle, radiator seems not to heat and no sign of water on the engine dip stick. Obviously a serious problem has occurred. Any thoughts
 

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angle - how crucial?

hi guys,
i did change my HG yesterday. i've tightened the bolts to 20nm, then i waited for about one hour and checked them again. all bolts had to be retightened.
after this, i've started the 90 degree sequence (4*90 turns).
problem and question is: i DON'T HAVE AN ANGLE METER/GAUGE, so i did this by sight. i did put some marker on the top of the bolt, but i'm sure it is not 100% accurate. so, HOW CRITICAL is that 360 degree rotation? i mean, if some bolts are a few degrees more or less, will it be ok?
thanks.
ps: does anybody know a final torque specification, so i can check all of them after the 360 degree turn?
 

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'06 ZR +120 (HQM) '04 ZR 105 (IAB)
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There is no 'final torque' setting - the 20Nm is to settle the gasket and ensure that the tightening sequence starts from the same point for all bolts. An angle tightening sequence is used instead of a torque setting so that all the bolts are tightened by the same amount and reach the same amount of extension it removes the effects of friction and torque wrench inaccuracy.

The 360 degrees is fairly critical but doesn't require an angle gauge - the genuine Kamax bolts have a mark moulded on them and when all the bolts are at 20Nm, you need to mark the alloy of the head next to each bolt to indicate where this indicator is pointing at the start of the angle sequence. Each phase of the angle tightening is not critical to within a couple of degrees, and on the final phase (at 360 degrees) the mark on the bolt head will again align with the starting mark you have made on the head.
 

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Thanks. Indeed, V. Reinz mention on their website that angle tightening is more accurate than torque. I did check my marks again, they look quite ok. because the marks were thick, there is no exact way to tell, but they do look good.

one of the bolts (no. 8) is a few degrees more tight (like somewhere between 12 and 1 o'clock, but more close to 12) and probably bolt no. 10 (the last one) is a few degrees less.

what can possible go wrong? i actually mean the question. like:
can i have damaged the gasket? can it be less tight and leak? can the bolts brake? and if the car will work, should i still worry for the future or not?
 

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MG ZT, Rover 25
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I'd leave it - you'd do more harm un-tightening and re-tightening if you are as close as you think. I've never used an angle gauge with a HG - just marked the bolts as MitC does.
 

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here is a short update:
engine is up and running. no coolant in the exhaust, nor in the oil pan. as far as HGF symptoms, everything is good.

on the other side, i can see the infamous coolant external "leak" around the alternator edge... although i wouldn't call it a leak yet, it is only a "humid" place...

should i just let it be? or should i tighten furthermore 45 degrees each head bolt? what do you think?
 

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MG ZT, Rover 25
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...on the other side, i can see the infamous coolant external "leak" around the alternator edge... although i wouldn't call it a leak yet, it is only a "humid" place...

should i just let it be? or should i tighten furthermore 45 degrees each head bolt? what do you think?
Could tighten a little. Danger is you'll break or overstretch a bolt if you do too much. I've tighten further before with exactly this fault on an FAI MLS gasket. It helped but didn't stop the lhs front leak permanently.

The other thing you could do if it persists after tightening is a dash of radweld gold in the coolant reservoir - I expect to get a hard time for suggesting such a thing! :eek:mg2:

However, if you have replaced the gaskets property and you know all is well apart from this small seep, it will probably stop it at less cost and hassle than redoing the job with an elastomer hg or getting a replacement engine. With the values of mg-r's measured in the hundreds nowerdays it could be a practical solution.
 

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let's say, if i decide to further tighten 45 degrees, i should just go ahead and tighten the head bolts (simple as that?) or i should loose them a little bit and only then re-tighten?

yes, i was also thinking about some radiator substance, but i'm not in a hurry with any of the solutions above.

thanks for the input.
 

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MG ZT, Rover 25
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let's say, if i decide to further tighten 45 degrees, i should just go ahead and tighten the head bolts (simple as that?) or i should loose them a little bit and only then re-tighten?

yes, i was also thinking about some radiator substance, but i'm not in a hurry with any of the solutions above.

thanks for the input.
Bear in mind this is not a recommended procedure and there is a risk of damaging a bolt.

If the HG is quite freshly on and I hadn't run the engine like this for long, and and if I knew where I was on the tightening sequence, I'd just tighten each equally, say 45 degrees more.
 

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update

so, i didn't retighten anything. that humid spot just didn't look like it was worth the trouble.

good news is that the engine is clean, dry and sound. i actually cannot see anymore leaking anywhere near the head (or in other places). also, there are no signs of evaporated coolant.

idle is very good and i did have to take the coolant out in order to fix some connections, so i took the opportunity and checked entire coolant... crystal clear, no oil stains, no other mud.

today i've passed the system bleeding with flying colors and i think this concludes my business on this thread :-D

thanks everybody for the help.
 

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metro
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I have a slightly sticky No 2 exhaust valve - gives erratic emissions readings and, perhaps around once a second, a slight hiccup in the exhaust rhythm, so the head will be coming off. It's the K8 as fitted to the Rover 100.

So this topic has been a valuable read, even though I replaced the head gasket around 5 years ago (with the first generation MLS + shim); I welcome this refresher - thanks to everyone. Being in no immediate rush to do the job has given me plenty of time to fully research the project; it's surprising how much info I've been able to pick up, not least of which was discovery of the existence of the modified "carbon-break" exhaust valve.

One tip I picked up to minimise/prevent coolant loss/weepage past the head gasket after fitting is to run, at idle for half an hour with the coolant system unpressurised to allow the viton coating on an MLS gasket to soften and bond to the mating surfaces without interference from weeping coolant, especially antifreeze, which lowers the surface tension of the coolant making weepage all the more likely. I had been contemplating first running the engine dry after fitting for perhaps 30 sec to a minute and letting it cool before adding coolant. And I may well do that and then run unpressurised to give the viton coating every chance to bond cleanly.

I also noted the absence of any mention in this thread of peening the fire-ring area (if indented) prior to machining to work-harden that critical area. In the trade magazine Professional Motor Mechanic (PMM) (Feb 2010), Ultra Parts, the manufacturers of composite and MLS gaskets, state "surfaces finishes should be commercialy smooth. A mirror finish is ideal" as well as "assembly conditions must be clinical". I don't wish to rekindle the skim vs no-skim argument, but the article states "heads should be refaced as a matter of procedure. Both the block and head faces must be flat and parallel within 0.003" of flatness." They also say not to panic if minor leaks are noticed between the head and the block because the viton or silicone sealing surface has to soften under initial run-up temperatures and, if neceassary, one should repeat the run-up procedure when cold to aid the self-healing process.

As mentioned in this topic, they state the liners must stand proud of the block. The PMM article states 0.002". I've more commonly seen figures closer to 0.005", but the one thing all are agreed on is that the liner heights above the block must be the same.

Head bolts should be lightly lubricated with engine oil especially under the bolt head and the head of any washers fitted. And Ultra Parts is adamant that no sealants of any kind should be used on the head gasket. (In my ignorance 5 years ago, I used Hylomar on the MLS gasket and shim without detriment, but I won't be repeating that error this time.)
 

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MG ZT, Rover 25
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One tip I picked up to minimise/prevent coolant loss/weepage past the head gasket after fitting is to run, at idle for half an hour with the coolant system unpressurised to allow the viton coating on an MLS gasket to soften and bond to the mating surfaces without interference from weeping coolant, especially antifreeze, which lowers the surface tension of the coolant making weepage all the more likely. I had been contemplating first running the engine dry after fitting for perhaps 30 sec to a minute and letting it cool before adding coolant. And I may well do that and then run unpressurised to give the viton coating every chance to bond cleanly.
Not heard this before - where did you get it from? I'd sooner run it unpressurized rather than with no coolant; that sounds a bit risky!
 
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