Head Gasket or Rings or something else?

[Lauren]

Well, it's that time again, my engine has gone again!

No,4 noted to be not working again (for a change).

Compression tested No.4 and it's 75 psi which obviously isn't good.

This time I've got oil dripping out of the air filter, so the oil is being compressed.

My best guess is a failure on the HG around an oil way on No.4

No.4 spark plug looks fine, it's geting a spark, but with only that much compression is basically doing bu88er all.

Suggestions welcome. Not best pleased would be an understatement as I only had this apart 6 months ago.

[Lauren]

Nobody got any ideas?

I'm going to take the head off at the weekend.

Still think it's HG, though if the block needs decking, it's scrap really.

[elbon50]

That is disappointing Lauren, after such a short time too

Expect you've covered a fair few miles during the 6 months though

Did the block surface look corroded in the No 4 area ?

Conjecture is of little value though and as you say head off then you'll know what's what

[PW@Woodsport]

Lauren did you have the head skimmed or just clean up the surface? First thoughts are 75psi is not indicative of a HG failure unless it was catastrophic, which the 4a is not known for. I'd lean towards it being ringlands again, which is pressurizing up your breathing and hence the oil in the filter.

I've never seen a HG fail between oil gallery and bore, it's always between coolant and bore, also was there any block corrosion around 4?

If it is ringland failure again i would be starting to think you have a fuelling issue on that cylinder, overfuelling causing borewash and premature ringland failure due to lack of oil protection. When you repair it this time i would definitely have your injectors flow tested or i can see that happening again.... i guess what i'm saying is i find it very hard to believe the same thing happening to the same cylinder within a matter of months as being coincidence, so it really does need looking into further.

At this stage you have no option but to strip and examine it again, check if your oil smells petrolly(?), and before pulling the head off just check number 4's buckets are all fully returning (valve clearances)

Do you have blue smoke coming from the exhaust?

[Lauren]

I didn't have the head or block skimmed Paul, when I swopped the block over.

My reason for suspecting the head gasket is that the plug is normal in condition. If the rings were gone I would expect an oily plug. This is what happened last time, so the symptoms are not the same.

I did not notice any corrosion. Mark fastidiously cleaned up the surfaces. I didn't check whether they were true or not.

I admit, if the block needs decking, it's scrap and I will just look at changing for another engine.

If the ringlands have gone as you say, Paul, then yes, I did suspect that there might be a fueling problem which wasn't addressed last time.

Again, if the bottom end does have to come out then I will look to see what it is, but this time, I'd likely just replace the whole engine for a stock one.

There was no smoke from the exhaust and no burning of oil as such. It doesn't seem to fit the criteria for the rings having gone.

I've covered 25,000 kms since I put it back together.

[IanParkhouse]

Lauren

Sorry to hear you having issues again. Get in touch if you need an engine

[Lauren]

I'm wondering if the harm was done on the way back from Duderstadt.

I drove 700kms (437 miles) in one go with only about four stops of around ten minutes or so.

When we got into Belgium the weather turned very warm. It was around 25C and rising outside. So, I pressed on at 120/130kph with the AC on full whack. I also have a whopping oil cooler in front of the AC condenser rad. The temperature gauge went up one notch, so I reduced my cruising speed to 110kph and after about ten to twenty seconds the temperature returned to normal.

It's hard to tell how much of a rise in temperature the engine saw as I have a digi-dash, so I'm not sure what the difference is between one increment and another. I will say though that the gauge has never risen before.

I then accelerated to a cruise of 120kph and after ten minutes the gauge went up again. I slowed again and it returned to normal.

I wonder if I was cooking the head gasket at this point? On the Tuesday (now 8 days ago) we drove from London to Manchester and again a bit of faster cruising around 120kph caused the same issue.

I didn't drive the car Wednesday, only on Thursday then again on Sunday. It was on Sunday that we noticed it was missing due to the lumpy idle.

[PW@Woodsport]

It takes a lot more than just a slight temp increase to cook a HG, you literally need to bury the needle in the red and drive it until it's red hot, i don't think you will have cooked it on your journey.

Doesn't sound ring related this time, but i still don't think it's HG with that compression reading, unless it has had a major breach, but i'd expect there to have been noticeable block corossion or head distortion, but as you say the head and block weren't decked or checked for flatness so it could be that.

Could also be a valve issue, more likely inlet due to the oil.

I think it's all conjecture at this point though, i think you really have to start taking it apart again, i would pay attention to the valve clearances before pulling the head off, just in case it's something simple.

[SuperRedMR2]

It takes a lot more than just a slight temp increase to cook a HG, you literally need to bury the needle in the red and drive it until it's red hot

I did this, but my HG was only slightly breached but I had block corrosion.

[Lauren]

Thanks, Paul.

I will check valve clearances and that there isn't a sticking valve. I guess it's possible.

If the head does need skimming I'll do it, thats not an issue.

[Icsunonove]

TBH this engine thrown together as a stopgap before fitting the 4AGZE or 4AGTE. It was a gamble and nothing was checked properly and that's the way Lauren had to do it at the time. There was no time or money to do anything else.

It might have failed immediately but luckily it didn't and has done a long euro trip without problem

The block was lying in Garrick's shed for years and it was bunged together with Lauren's original head without any checks.

The block:



Once cleaned up there was no major corrosion worries, but it may well not be flat as could the head:



So I actually think it's done quite well. I don't know what Lauren's plans are now.

If that engine's staying it really needs inspecting and rebuilding properly IMHO.

[elbon50]

TBH this engine thrown together as a stopgap before fitting the 4AGZE or 4AGTE. It was a gamble and nothing was checked properly and that's the way Lauren had to do it at the time. There was no time or money to do anything else.

It might have failed immediately but luckily it didn't and has done a long euro trip without problem

The block was lieing in Garrick's shed for years and it was bunged together with Lauren's original head without any checks.

The block:

Image Replaced With URL For Quote http://url.photobucket.com/albums/v284/ ... 00x600.jpg

Once cleaned up there was no major corrosion worries, but it may well not be flat as could the head:

Image Replaced With URL For Quote http://url.photobucket.com/albums/v284/ ... 00x553.jpg

So I actually think it's done quite well. I don't know what Lauren's plans are now. Itf that engije's staying it really needs inspecting and rebuilding properly.

All will be revealed this coming weekend

I take it you'll be helping ?

[pk_090]

I also might pop up and lend a hand if required. I owe you guys a favor for the help you gave on mine at the start of June!

[Icsunonove]

I take it you'll be helping ?

Well not unless I have to, I've had enough of engines this week. There's only so many pairs of hands you can utilise before people start getting in the way. Anyway, it's hard work working with Lauren, she's like a bull in a china shop and wants everything done yesterday!

And in any case I've got my own block corrosion problems at work, I'm trying to rebuild this and make it work again, the block face is properly corroded





It reminds me of this:





Of course I will help if required though

[pk_090]

That that a beemer straight 6 Tom? Yeah does look abit aero bubbly
Alex

[Lauren]

That that a beemer straight 6 Tom? Yeah does look abit aero bubbly
Alex

Aston Martin crap, I believe.

[elbon50]

Nice new wet liners Tom

Looks like you'll need to take quite a bit off their tops to get the block down to good metal though

I used to drive an old Aston

Went like stink but rod operated brakes which were dreadful

Try as we might we couldn't get the old girl to stop

[pk_090]

What on earth do you do Peter?! Not a massive fan of aston's due to them all being identical the old ones to the new ones, but i do appreciate the engineering that goes into them!

[elbon50]

What on earth do you do Peter?! Not a massive fan of aston's due to them all being identical the old ones to the new ones, but i do appreciate the engineering that goes into them!

LOL

Was remembering back a long way then Alex

The Aston with rod operated brakes was a pre WW2 car

Low slung and gorgeous looking, with sweeping wings & running boards

I can never forget that car

Managed not to crash it, despite the terrible brakes

[Lauren]

We'll be doing all the diagnostics on Sunday before whipping the head off.

Will report in due course.