Time to say goodbye ?

First of all gents thankyou for your feedback. It is greatly, greatly appreciated!

Plan is I'm going to clear space in the garage and get her in there and up on axle stands. I'll test everything you've all suggested and report back with my findings this weekend.

In preparation I think I may as well just order a new rocker cover gasket now. If I can establish that it is the cat and remove that from the chain to relieve pressure, at least then I can fit the new gasket while I wait for the new cat to arrive. If I can't get the cat to budge I'll likely take the whole exhaust out past the manifold and remove it that way.

I need another back box anyway as I (stupidly) went into a stupidly bumpy lorry yard and hit it from underneath which caused the left side arm that holds it up the car to snap off. So the left tail pipe is looking rather sad and currently sitting on the bumper. Shame I don't know a welder.

Notanumber wrote:

I'm in Bristol & it's a 135 

I always try to recommend the checks that cost nothing more than elbow grease first before getting into potentially more costly diagnostics.
Once you've  settled upon the cat as a contributing culprit, the sole culprit or or even cleared it's name, we will guide you through any further actions required.

You mentioned welding. it's worth you doing a shout on this and the other forums and maybe the F/ TF farcebook pages asking for any owners in your part of Bristol who could pop by with their mig welder for a few beer tokens. Include photos of what needs welding.
Most owners are usually happy to help out another and there are lot of us with mig welders. Unfortunately I'm on the opposite side of the country otherwise I'd do it.

Okay gents so finally got out and under the car. This is as far as my diagnostics went today.

Checked the oil filler cap. Was clean as a whistle and wasn’t puffing with engine on. There was some exhaust coming from the tail pipe. Seemed normal.

I bought the digital thermometer gun and measured the cat with it as David suggested. Low and behold the inlet side temp was nearly double than that of the outlet side.

So a new cat and camshaft cover gasket and hopefully all should be well fingers crossed.

I tried to get at the cat bolts with some penetrant and a spanner but was very much unsuccessful in getting them to budge. I’ll lend an impact driver and see if that helps although looking elsewhere on the forum it looks like I'm going to have to drop the whole exhaust out past the manifold and employ an angle grinder on the cat bolt heads (and whatever else to get the studs out so the new one can actually go on).

Once the cat is out, if you find that the matrix has broken up, you need to ask your self where has it gone? The answer is it's probably in the rest of the exhaust down stream of the cat and is probably choking the flow through a muffler.
There are a few types of catalyst matrix one is a rock like ceramic honeycomb and the other is like a foil mesh honeycomb, this latter type is often found in high flow performance cats , but it is also found in cheap and nasty ebay rubbish from China, it can brake up and bits can do a excellent job of blocking the internal baffling of your muffler.
The former type is what is found in most OEM cat converters, it is more durable, however it to can brake up into little bits with age and vibration, these bits can rattle about in the exhaust system they may just block the exit pipe of the converter. or they can be finding themselves down stream also causing other restrictions, you may however be able to shake most of it out of your muffler if you're lucky.

What also happens is if the ceramic matrix can also over heat, then it can block up as it melts.
it can overheat due to excessive unburned hydrocarbons getting into it there can be many causes for this, such as dirty injectors, poor tune, ignition problems, etc. not to mention our old favourite: a blown head gasket!

Cat converters can also fail due to poisoning, leaded fuel can put a coating on the catalyst, preventing it from reacting, lubricating oils that use zinc and/or phosphorus additives will also poison a cat, as can silica which can find it way into the cat via coolant getting into the exhaust or the use of the wrong types of gasket sealants (most silicone types, there are some that are OK for use with cat converter equipped cars, it will state this on the packet, so read it!) I myself, prefer NOT to use silicone sealants, and in the rare occasions when I do, I apply them sparingly.

 



 

Thanks Cobber, there is always some useful takeaway from one of your longer pieces.
It really didn’t matter how many summers you have seen a Cobber knowledge nugget is always informative.
Now we have Christmas in the rear view mirror & with that grump subsiding, what are you feelings on the coming new year, is that still humbuggery?
M

In a nutshell...yeah and my new year resolution is to have no bloody stupid new year resolutions! 🤣

Good on ya mate!
My New Years resolution is to keep breathing, keep thinking coherently, keep walking, keep scrabbling about under the car, keep coming up with fresh ideas & putting them into practice.
That will do.
M

Had to cut the old exhaust out today which was a pain but got it done with new backbox and cat fitted. Upon proper investigation of the downpipe I could see it had been welded very badly at least twice in the past and had holes in the welds so I've done away with that and have another ordered.

I started disassembly on the engine to replace the camshaft cover gasket and when I was removing the coil packs was quite shocked to see one of the spark plugs come out with it.

That would explain the pop and the lack of compression up that A-Road. I took the plug off the ht lead and tried to screw back in but it span with very light torque. So whoever has worked on it in the past has knackered the thread and it's eventually just unwound on what it had and blew out.

I'm looking at a heli coil to rectify the issue. Has anyone done one of these before on a K ? What did you use/how did it go/what was the outcome ?

From the research I've done this evening these seem to be the trick (Save-A-Thread) > https://www.amazon.co.uk/Helicoil-5334-14-Thread-Thread-Repair

As a side note, the cam cover gasket that was already installed seemed perfectly fine. No Damage at all. Although there is evidence of oil leaking from that location so I put the new one on anyway. The new genuine MG Rover one I had seemed to have a porous material coating the metal unlike the one I removed which was just a standard sheet metal gasket.

Pretty much all 4 of the spark plugs were oily/sooty. No signs of wearing away or anything.

Thankyou to everybody for your help so far. Any advice as always appreciated 

I don’t have first hand experience with Helicoiling a plug thread, although I’m aware of it being done with great success. Of course there will be naysayers, but hopefully not within our community.
Obviously others are invited to add to this if there’s a divergence of opinion.
Cobb’s is usually an excellent bellwether on such things, I’m sure he will have words for us.
Please keep us informed of your progress, as you have noticed we are nosey buggers.
M

Yeah a helical thread insert should do the trick, I not had the need to do one on a K series engine but I've used them on many other engines.
So whilst I cant give you a guide tailored to the MGF/TF, I can give you a generic one.
Give me a little time to write one, I can probably do it today as it's pissing rain outside so I've got bugger all else to do today!
 it will be posted in the how to section for posterity, it will be for general thread insert needs with dedicated info for sparkplug threads.
I will post a link here when done.
 

Here is the link as promised: https://www.the-t-bar.com/forum/tooltime/99341-how-to-use-helical-thread-inserts-including-tips-for-spark-plug-threads
I've didn't put it into the How To's as  there is so much stuff it in there it's likely to be too hard to find. Seeing as it's really a tool specific how to I put it into ToolTime to keep it separate from the job specific MGF/TF Howv To's
I will in time do more tool specific how to's  which
I intend to place in ToolTime.

And I should do a tread on how not to bugger up  your spark plug threads probably tomorrow if I have time.