GT6 Boiled Over...

[Gary Flinn]

65-70 lb/ft is correct for the Cylinder head nuts for the later engines with the larger Studs/Nuts, could this be the issue?

[Iain T]

Kevin's profile says mk3 so it should be the higher torque setting. This could undoubtedly be the cause. 

Iain 

[johny]

yes here we go:

[Ian Foster]

Interesting, not seen that before. My factory WSM covers Mk1, Mk2 & Mk3 and yes 60-80lbft for the MK3 on page 0.116 Fourth Issue. Just not looked at that page before, as I have a Mk2.

Strange that is significantly higher than the Mk2 (+15% on the upper figure) and a with a much greater range as well.

Hopefully this information will be useful for Kevin.

Ian

[johny]

I wondered if the recessed type block made a difference but I think the mk 3 came in both types and the manual torque figure doesnt seem to distinguish between them. As you say either way it looks like Kevin under torqued his head...

[Kevin Atkins]

10 hours ago, Ian Foster said:

You said you had re-torqued to 44lbft.......

Hi Ian,

Yes it's a late Mk 3 - I've got two Haynes manuals (one was a Christmas present..), the first manual is an older imprint that doesn't appear to cover the later cars properly (even though the cover shot is a Mk 3), the second manual is an up-to-date edition that I found some additional data in for the Mk 3's .. and exactly as you and Johny suggest, 44 lbft is too low.. I hadn't realised, nor was I aware of the different rad cap ratings for the different iterations - I'm pretty sure I put a 13 lb cap on but I've ordered another 13 lb to be certain, and also in case the rad cap is a factor in all this..

Anyway, I torqued the head nuts up to 70 lbft earlier, pedestals to 30 lbft, and checked valve clearances after doing this - all seem pretty much on the nose at 10 thou, so it looks like the head is now fastened down correctly and valve gear is fine. However, compression readings remain a good 20% lower than they were before I stupidly released all the head nuts instead of one-by-one, so I think I've probably messed up the sealing.. I fear I'm going to have to take the head off now to sort this out, stupid rookie mistake..

Still very much learning the ropes with this, and still learning about the subtle differences between the model years etc. Really appreciate the help and support everyone has given me, making plenty of mistakes but trying to learn and correct as I go!

[Iain T]

We all learn by our honest mistakes. At least it seems as though the problem has been identified 🤞

Iain 

[johny]

24 minutes ago, Kevin Atkins said:

However, compression readings remain a good 20% lower than they were before I stupidly released all the head nuts instead of one-by-one, so I think I've probably messed up the sealing..

Just for reference I dont think I would have released any head nuts but just tightened them up more to the correct higher figure following the pattern indicated in the manual. This is basically a head retorque that is recommended when a few miles have been done after a gasket change...

[cliff.b]

1 hour ago, johny said:

Just for reference I dont think I would have released any head nuts but just tightened them up more to the correct higher figure following the pattern indicated in the manual. This is basically a head retorque that is recommended when a few miles have been done after a gasket change...

Interested that you suggest not loosening nuts during a head re-torque. I'm almost at the mileage for doing mine after my recent head gasket replacement and most advice seemed to be to warm the engine, slightly loosen each nut then re-torque before moving on to the next one. Not sure what the reason for the loosening was though.

[Ian Foster]

Kevin

Looks as though the issue has been identified with respect to HG clamping. 

Head off and gasket change is probably the only logical step at this stage. IIRC stud threads should be lightly oiled prior to installing nuts and torqueing up. Best to torque-up in stages.

From your original post I'm not sure the head has been off before in your ownership, so at least you'll have the change for a good de-coke and polish up.

At least you will have some advice to follow on the cooling system refill.

Please keep us posted re progress and results.

Ian

[Kevin Atkins]

11 minutes ago, cliff.b said:

Interested that you suggest not loosening nuts during a head re-torque. I'm almost at the mileage for doing mine after my recent head gasket replacement and most advice seemed to be to warm the engine, slightly loosen each nut then re-torque before moving on to the next one. Not sure what the reason for the loosening was though.

I think my mistake was that I loosened all the head nuts, rather than just doing one by one.. so whatever you do, don't do that! Do it one at a time - I've just watched a YouTube video of a chap doing exactly what you're about to do on a Citroen DS following a recent HG change, and he went through each nut in turn in the correct tightening order, backed off a quarter turn with a breaker bar, then re-torqued, and moved on to the next

[PeteH]

The Theory behind backing off and tightening Nuts/Bolts, when re-torqueing. Is based on the possibilty of the nut having possibly slightly seized, the backing off, "ensures" the thread is as free as possible, and less chance of an error.

Pete

[Kevin Atkins]

2 minutes ago, Ian Foster said:

Kevin

Looks as though the issue has been identified with respect to HG clamping. 

Head off and gasket change is probably the only logical step at this stage. IIRC stud threads should be lightly oiled prior to installing nuts and torqueing up. Best to torque-up in stages.

From your original post I'm not sure the head has been off before in your ownership, so at least you'll have the change for a good de-coke and polish up.

At least you will have some advice to follow on the cooling system refill.

Please keep us posted re progress and results.

Ian

Thanks Ian,

Yes, if only for peace of mind, at this point I think I've got to pull the head and make sure everything's in order. I will be making close reference to all the posts in this thread regarding cooling system bleeding though, so I get it right.

I've got a feeling the head has been off at some point before though - some washers were either missing or of differing type on the rocker pedestals.. But it's unlikely the head has been removed in at least the last 20 or so years as the car has been out of action for a long time, so hoping it's not too much of a job to get it off!

Cheers,

Kevin.

[cliff.b]

7 minutes ago, Kevin Atkins said:

I think my mistake was that I loosened all the head nuts, rather than just doing one by one.. so whatever you do, don't do that! Do it one at a time - I've just watched a YouTube video of a chap doing exactly what you're about to do on a Citroen DS following a recent HG change, and he went through each nut in turn in the correct tightening order, backed off a quarter turn with a breaker bar, then re-torqued, and moved on to the next

Did he explain why he backed them off first?

[Kevin Atkins]

2 minutes ago, cliff.b said:

Did he explain why he backed them off first?

I think Pete's explanation a couple of replies above makes sense, I can't remember whether the reasoning was mentioned in the video, and all cars are different I guess (especially Citroens 😜 )

Here's a link to said video -

 

[cliff.b]

9 minutes ago, Kevin Atkins said:

I think Pete's explanation a couple of replies above makes sense, I can't remember whether the reasoning was mentioned in the video, and all cars are different I guess (especially Citroens 😜 )

Here's a link to said video -

 

Thanks. See he is doing it with the engine cold.

[cliff.b]

22 minutes ago, PeteH said:

The Theory behind backing off and tightening Nuts/Bolts, when re-torqueing. Is based on the possibilty of the nut having possibly slightly seized, the backing off, "ensures" the thread is as free as possible, and less chance of an error.

Pete

Ah, I missed this post. Makes sense.

[johny]

23 minutes ago, Kevin Atkins said:

I think my mistake was that I loosened all the head nuts, rather than just doing one by one.. so whatever you do, don't do that! Do it one at a time - I've just watched a YouTube video of a chap doing exactly what you're about to do on a Citroen DS following a recent HG change, and he went through each nut in turn in the correct tightening order, backed off a quarter turn with a breaker bar, then re-torqued, and moved on to the next

I got mixed up as I was thinking youd already replaced the head gasket but with an old used one the retorque was a very long shot so highly unlikely youve lost anything🙂

[Kevin Atkins]

6 minutes ago, cliff.b said:

Ah, I missed this post. Makes sense.

Yeah there were a few replies in quick succession 🙂

[Kevin Atkins]

4 minutes ago, johny said:

I got mixed up as I was thinking youd already replaced the head gasket but with an old used one the retorque was a very long shot so highly unlikely youve lost anything🙂

Yeah, kind of worth a try.. I was hoping it might work but as it is, I'm not going to chance running it, just asking for bigger trouble otherwise I think. And it's another learning experience - I've kind of got more of an intimate knowledge of this little car since owning it than any other I've owned.. back end rebuilt, took a couple of tries to sort that - the nagging feeling I've not done it quite right, go back and rework as necessary, now it's spot-on - drives down the road turbine smooth. That's also thanks in no small part to the sterling work Mike Papworth did on the diff + gearbox rebuilds! But I really, really want to be able to jump in and just drive it now!

[Ian Foster]

Kevin

Remember that you will have to re-torque the head after about 500 miles.

Ian

[Kevin Atkins]

7 hours ago, Ian Foster said:

Kevin

Remember that you will have to re-torque the head after about 500 miles.

Ian

Thanks for the tip Ian, appreciated.. I don't want to be doing this again any time soon! Head is off, which is a relief as I'd read some stories of real grief budging it, but a lump of wood and mallet shifted it once I'd got the studs out.

Cheers,

Kevin.

[Iain T]

54 minutes ago, Kevin Atkins said:

I don't want to be doing this again any time soon!

It gets easier after the third or fourth time 😂

Don't forget the hardened washers and correct grade of nuts. 

Iain 

Edited July 6, 2023 by Iain T

[johny]

And of course the right type of head gasket👍

[Kevin Atkins]

2 hours ago, Iain T said:

It gets easier after the third or fourth time 😂

Don't forget the hardened washers and correct grade of nuts. 

Iain 

🙂 .. Yeah, I became quite adept at doing head gaskets on Minis back in the day.. a couple I owned shot their gaskets, seemed to be a 'Mini thing' and part of the charm..

This hasn't been as bad a job as I was thinking it might be - much bigger engine than an A Series, I was envisioning having to call in help to lift the head off but it was lighter and less cumbersome than I was anticipating.

Got new studs, nuts and hardened washers on order - three of the studs in particular, adjacent to the exhaust ports, were very stubborn and the stud extractor jaws left some pretty deep gouges so I thought it better safe than sorry, just order new (they're not exactly cheap though.. ouch!). Just need to finish cleaning up the mating surfaces, and the pistons are covered in coke so I might clean that off while I'm at it.. I could get carried away but the engine seems otherwise healthy, bores look good, so I'll leave everything else alone I think!

Cheers,

Kevin.