KV6 lower inlet manifold gaskets.

[Elliott]

Could it just be badly warped machined surfaces, Is it worth a proper strip down, use a straight edge across the various areas of failure, then a skim at an engineering shop, Rubbing down with sandpaper could cause tiny ridges to appear on the surfaces allowing water to pass along the gaskets.

[Typhoon190]

The thermostat housing has failed around the join. Apart from the initial failure of the original, the following two have failed when the correct coolant level hasn't been maintained, by me. My assumption was that there is increased pressure in the housing, as the level drops below the housing height, causing it to fail. (100 degree plus running temperature, but steam/vapour present in the housing rather than liquid coolant, due to low level. )

Admittedly, I haven't matched the fitment made by the factory, but I agree with Kaiser, that there's a high risk of the gasket failing due to the material.

[DMGRS]

We still have some kits @ £29.99 if you're stuck.

[SD1too]

Originally Posted by Typhoon190

The thermostat housing has failed around the join.

I think you will find Ben that it's the 'O' ring which is leaking and spraying coolant upwards which then solidifies around the seam. That was the case with mine. I proved it by testing and refitting the original thermostat housing but with a new 'O' ring. It didn't leak any more.

By the way, are you using OAT antifreeze at 50% concentration like me?

... causing it to fail. (100 degree plus running temperature ...

Have you checked that your radiator fan is working correctly on all speeds? What is your actual running temperature read from the IPK diagnostics? It should be in the low nineties when the car is moving.

Admittedly, I haven't matched the fitment made by the factory ...

It's therefore quite possible that you've been using parts of inferior quality. The obvious thing to do is to fit a pair of genuine X-Part gaskets bought from an ex-MGR dealer, not e-bay (unless they are supplied in sealed MGR packaging). I'd be very surprised if that doesn't solve your problem.

Simon

[Typhoon190]

Originally Posted by SD1too

I think you will find Ben that it's the 'O' ring which is leaking and spraying coolant upwards which then solidifies around the seam. That was the case with mine. I proved it by testing and refitting the original thermostat housing but with a new 'O' ring. It didn't leak any more.

By the way, are you using OAT antifreeze at 50% concentration like me?

Have you checked that your radiator fan is working correctly on all speeds? What is your actual running temperature read from the IPK diagnostics? It should be in the low nineties when the car is moving.

It's therefore quite possible that you've been using parts of inferior quality. The obvious thing to do is to fit a pair of genuine X-Part gaskets bought from an ex-MGR dealer, not e-bay (unless they are supplied in sealed MGR packaging). I'd be very surprised if that doesn't solve your problem.

Simon

Hi Simon.

I can't be 100% certain as to where the thermostat failure is at present, but will try and be decisive when I get round to changing everything . . . again. Concentration started at about 40-50%, but honestly, I've generally topped up with water, and then on the odd occasion OAT, since September last year when I last changed everything.

I have always used genuine MG Rover gaskets and thermostat kits, purchased either from Rimmer Bros, or Endon services. Stainless coolant rail fitted, and fan working on all three speeds inline with IPK readings. ( 100 on, 95 off slow speed etc).

When coolant level is correct, engine temperature sits happily between 88-93, but pretty stable 90 on motorway cruising speed.

My problem is that ever since the first thermostat failure, must be over 4 years ago now, the coolant level has always dropped at a fairly consistent rate, and looks to be entering the engine somehow. After about 5 months, the oil needs to be changed because of the mayo effect.

[Typhoon190]

Had some time off this week, so have tackled this again.

I think Simon's diagnosis regarding the O ring is correct at this stage. The coolant appears to have been leaking around this seal, and not the join in the housing.

The inlet manifold gaskets look to me to have failed again. This would be almost straight after fitting them last September, as I've been topping the coolant up consistently for a long while now.








I have always used genuine parts. I tighten the lower manifolds using a torque wrench to 38Nm as stated in the Haynes manual I have. Can anyone confirm this is the correct torque setting please?

[kaiser]

The inlet manifold gasket do not just appear to have failed. They have failed.
The material is unsuitable for the task, as it absorbs water into the paper and the high pressure gradient between the pressure of the coolant and the vacuum of the inlet, makes water migrate from high to low pressure.

Buy a sheet of water and petrol resistant gasket material and make your own. These originals are clearly a waste of time.

As for your thermostat housing, that material is unsuitable as well. It is just a matter of time. The originals seem to have lasted much better than the later Chinese made units, which literally crumble within a year or two, faster in hot climes.

[SD1too]

Originally Posted by Typhoon190

I think Simon's diagnosis regarding the O ring is correct at this stage. The coolant appears to have been leaking around this seal, and not the join in the housing.

Thank you Ben. What is happening? Yours is the second endorsement I've had from V6 owners in recent weeks.

I tighten the lower manifolds using a torque wrench to 38Nm as stated in the Haynes manual ...

Ben; I can't see 38 Nm mentioned anywhere on page 2B•2 of the Haynes manual. For the inlet manifolds, Haynes gives the same figure as MG Rover which is 25 Nm. You have therefore been overtightening them. That is the most probable reason why they have prematurely failed.

Simon

[Typhoon190]

My mistake Simon. I had 38 Nm in my head for some reason when typing. I tightened them last time to the 25 Nm figure stated in the Haynes manual.

All I can do is try again, or try an alternative as Kaiser suggests. I can't understand why I don't seem to be able to get them to seal, when they were clearly ok for a number of years originally.

[SD1too]

Originally Posted by Typhoon190

I can't understand why I don't seem to be able to get them to seal, when they were clearly ok for a number of years originally.

MGR mentions cleaning the cylinder head and manifold mating surfaces as well as tightening the bolts progressively from the centre outwards. Did you do both of those things?

Simon