Time to say goodbye ?

Now Cobb’s you can say in one breath that it’s constipated & that it’s shat itself on the other.
There is good reason to be suspicious of the internals of the cat, that would create the blow by & increases the crank case pressure.
The chances of “easily” dropping the cat out to test is unlikely, even a recently changed unit can be reluctant to depart.
It is, however, worth the ball bust to eliminate that & that will give you the opportunity to change the fixing hardware. You are guaranteed to wreck the original.
Of course if you were local to one of our number, if they were willing & technically proficient, I’m sure they would spare a few minutes.
I would & so would Cobber, but he’s sunning himself in an Australian summer; that would rule him out.
M

Yep sunning is the word.....41C today! Hotter than a curried fart.........Most unpleasant!

It is possible to diagnose a blocked cat by temperature. Something like one of these is invaluable.(£12 on amazon)
 

The cat inlet temp will be significantly greater than the outlet...

Try removing one of the breather pipes between the engine and the inlet manifold. That should give you some clues if it is over pressure.

Now there, gentlemen, is a great idea!
M

I’m a bystander in this topic and can add little I’m afraid.
But I am very interested to learn more about oil coming from the cam cover gasket area.
12 Months ago mine was showing some seepage down a couple of spark plug recesses. I had mentally prepared myself to tackle this job but on lifting the engine cover found a lot less oil down the plug holes than I had expected but some down the sides of the cylinder head. Alll the screws holding the cover in place were loose. So I have tightened them with the intention of monitoring the situation rather than leaping into a gasket change.
The point or relevance is this . How tight are the screws holding the cam cover in place?

My next question relates to the cam belt. When was it last changed? Has it jumped a tooth? That would no doubt set the MIL warning light off as crank and cam sensors together with the ECU would be asking each other questions.
Apart from that i defer to the experts and will watch this with interest.
 

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! 🤣