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MG MGF Technical - HGF or worse?

As noted earlier in the week,(see coolant loss thread) I suffered an HGF on Thursday last. I contacted the garage today to find out when the car would be repaired but they said they are waiting for parts. Apparently a new head is required. Is it relatively common that when the gasket goes the head gets damaged? or is the gasket likely to be a sympton of the head going?

Cheers
Alan
Alan Dunlop

Oh dear - sorry to hear that Alan. IMHO most HGFs wouldn't require a new head. Did they say what was wrong with it? Cracked? Soft? Warped too much for a skim? Any of these could have been the cause of the HGF failure. Or alternatively, they could be the knock on affects of an HGF if the car seriously overheated. Did you drive it after the HGF?
Dave Livingstone

Has anyone carried out a torque test on the head bolts after an HGF but before repair procedure starts? I've looked at the head pulldown procedure for a couple of other ally motors and it is quite complex compared to a K series. Like, two torque figures, followed by one angular figure, followed by angular relaxation, then torque again and finally retorque after 200 miles.
Has anyone else seen something similar.
Ken Waring

>. A quick glance at the gauges confirmed worst fears,
>both were in the red. As I was only about 1.5 miles
>from the nearest (good) MG dealer I was able to get
>there with a lot of coasting. The red light only came
>on as I entered the forecourt.

For reference, if the gauge reads _anything_ over the normal then you should stop - You didn't and it is not much of a surprise that the head is compleatly trash - but then as your not paying for it I wouldn't worry about the head.

I would worry about the red light as that indicates that the oil had lost pressure, and this only happens when the oil is _VERY HOT_ and it might have damaged other items - like the plastic oil pick up, but you should know this as soon as you start it, or at the latest after a few sharp bends.
Will Munns

>>and finally retorque after 200 miles<<
I don't know any mass-produced car engines which require this - can you give some examples ?
I'm not saying there's no benefit in these techniques - just that the car industry has moved away from anything that requires a repeat visit to the dealer.
Steve

Alan - I agree, the illumination of the red dash lamp is a terminal sign: if you weren't covered by warranty, I would strong advise you switch off the engine at the first indication of trouble, and get the car transported to the garage...

Regarding the torque procedure on a K-series, there is no final torque figure. You torque to 20 Nm in sequence, and then turn the bolts through 180 degrees in sequence, and then repeat the 180 degree turn once more.

Difficult to know what torque figure you'd end up with - as it depends on the elasticity/plasticity of the long bolts...
Rob Bell

Steve,
What you say is true. The 200 miles bit does relate to slightly older engine but e.g. Renault V6(R25) replaced this with run engine until hot, cool for 6 hours then continue procedure, tighten all head bolts then completely slacken all etc. etc.
The point I was trying to make (and failed) was that some other manufacturers have more exotic procedures than MGR, Nissan SR20DE is another. I assume the procedures are designed to achieve uniform tension and compression.

Rob,
The point of torque test is not to obtain an absolute measure of the torque value but to obtain comparative readings. Is there a large difference across the head, if so where? Does it mean something or nothing? There seems to be enough info to suggest that there is a weakness. There are a few theories and solutions but no engineering data. Just a suggestion for a starting place.
Ken Waring

Ah, I see where you are coming from now Ken. Certainly, this is an idea that's been discussed before.

An unequal loading might suggest that the head clamping forces are uneven - be that due to casting problems or uneven/incorrectly set wet liner heights.

Trouble is, because the stretch bolts are designed to, er, stretch, and measure of torque is quite likely to be misleading and unreliable. But that's my guess: might be worth chatting to an experienced K-series engine builder (Dave Andrews springs to mind) and getting their opinion.
Rob Bell

Hi Ken,
we had this topic up some years? ago but nothing really came out of it then,it ended up in endless discussions about the stretch-bolts and their function... I know exactly what you mean,it would be interesting to measure the un-wind torque of the bolts after an HGF and note the figures.
This regardless if the bolts are of the stretch-type or not! As mentioned several manufact. has gone for re-torquing the head -bolts after some initial run-in. Some admit it,some dont! The amount of jobs done on cars still on warranty that the customer is unaware of is hughe,Volvo is an expert on this... SAAB has for some time initiated a re-torque of the head-bolts due to HGF-problems. Going from composite to stainless steel shim type of HG seems to speed up the HGF-problems for them....
Anyone volunteer to take a torque measurement on the next HGF ? Mike ? Dave A?

BR, Carl.
Carl Blom

>>The point I was trying to make (and failed) was that some other manufacturers have more exotic procedures than MGR<<
I think you made a very valid point - especially given the long through bolts that MGR use, and the way the K series engine has been pushed out to 1.8L; I would though argue that most MGFs only suffer one HGF, so perhaps it's a problem with initial assembly rather than workshop practice?
I keep meaning to install a coolant level monitor to my F (a rising temp. indicator is too late), but I'm just too lazy - perhaps over Xmas ?
Steve

Coolant level monitor? It's a good idea - certainly something that we've all talked about aplenty over the years (like Tim Green's suggestion - http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=archiveth&subject=69&subjectar=69&thread=2001112009302132399)

Reading up on this subject, noticed a comment made by Roger Parker:
>>
Many header tanks from the days of the Rover 3500 SD1 have had coolant level sensors within. The recent Range Rovers continued this theme. Problems is that the coolant level surges and so it is likely to see many a false warning. It would be possible to enlarge the volume of the header tank considerably so the surge would have a lesser effect and then you may actually be able to achieve progress.
<<

Any thought on this?

BTW Steve, which indicator do you plan to fit? Bruce's system as featured on Tony's web site http://www.apttony.co.uk/Servicing/WarningLights.html ? Looks good...
Rob Bell

I was planning to use a reservoir with a float-type sensor - from a different car, I'm not planning any development work here, wired into an audible alarm (easier to place than a light). But I have to work on my Suzuki first!
Steve

This thread was discussed between 15/12/2003 and 17/12/2003

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