Croc

Start psyching yourself up for a full tear down and rebuild. The etching is a tell tale of the engine running really lean at some point. If your piston tops look like that then its likely there is damage elsewhere.

I will bet you have a ZSG416 as this was the Ford Power Crate 1.6 Sigma (also called a Duratec at one point). Fords nearly always have their stamped numbers near the starter motor mount. Also look under the exhaust manifold.

Don't trust the Caterham website notice. Always give them a call to find out the parts and the lead time. They frequently show out of stock when its an available to order part. You will need the engine variant number to be sure what you are ordering.

@Vovchandr Vlad - I guess trailering to the compressor is not an option? If you cannot do that then yes, you are at roll the dice point on a gasket change. Cold cylinder could be numerous things, e.g. lack of spark, lack of fuel, lack of air to fire combustion, etc. It could be Number 4 is not retaining compression and will not produce combustion thanks to the gasket fail (but plug on that cylinder should show richness in that case). Smell on cat will be contaminant leaking in - sweet smell is coolant (but you do not have that) and burning smell is unburnt fuel from the pistons being combusted in the cat. Neither are healthy for it. However, gasket fix takes priority as you have good odds for identifying/fixing this new problem as you dismantle and reassemble.

First observation I would make is that your sump is not the one I have seen on the UK Caterham Sigma cars I have driven regularly. Their sumps look like this one: Wet Sump Kit - Sigma (caterhamparts.co.uk) If you want to go dry then there are two options I am aware of. Premier Power are the Sigma specialists Dry Sump Oil System Installation - PREMIER POWER (premierpowerengines.com) AT Power has a dry sump but I dont know anyone who has used them Ford Sigma/Zetec Dry Sump Kit (atpower.com) Lastly, these engines were used in Formula Ford in the UK. There was a Ford Racing replacement for that application. Never seen one. I assume it is a baffled wet sump. Don't have a link sorry.

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@fastg Stop it Graham, I was trying to wind up John!

Holy crap! That does not sound like an M10? Before you let it go, you have to track it at least once. Then you really know if you built it right. Is your local track Carolina Motorsports Park? If so then you want to look up Maureen and Steve who are now regulars there after moving south. Steve runs a Birkin 7 on track. Roughly your HP - it would be a good match up with your 420R. Maureen runs a supercharged Exige so you wont know which way she went!

That smoothed things out nicely. Intersection of power and torque curves is at a good point for being usable on the road without stressing the engine.

Calling @simon450 to this thread.

Welcome Ugly! I love the Bimmer! I have a soft spot for that era. Any better photos of it? Actually I should just search your instagram feed....

That should be thrown away immediately. What type of metal is that to get such corrosion in a 2001 Caterham?

@VovchandrI don't think you have ever told us how you know your coolant rail is rusty? Coolant rails normally don't go rusty or flaky on 20 year old cars. I have cars of all makes up to 55 years old, some truly basket cases, and have never experienced a rusty coolant rail. Is this somehow simulating a head gasket fail from a blockage?

@seschm1234 But its not my list thats important, its the process of methodically thinking through the problem that is key. Besides, I am not convinced its solely the head gasket. I suspect the head is doing something to contribute to the problem but I don't have enough to pin-point it. It may be that we only discover when Vlad takes the head off to fix the gasket. Vlad deserves a beer for persevering with this

So lets roll through the symptoms and results of the various tests observed: No white smoke - that would be indicator of coolant leak into cylinder No blue smoke - that would be indicator of oil leak into cylinder Spark plugs are all similar color to my eye - if one was clean then that is an indicator of coolant leak into a cylinder No visual leaks of oil or coolant between head and block Oil cap on cam cover was not showing, foam, sludge or mayonnaise inside - that would be indicator of coolant in oil Expansion tank overflow - clear evidence of bubbles & over-pressurization. Repeatedly happens after re-bleedng. Could be tank cap faulty or form of head gasket failure? Variety of tank caps tried - no alteration of end result - over-pressurizing Expansion tank - No sign of mayonnaise or foam - that would be an indicator of oil in the coolant Expansion tank - no oil slick or scum on the surface - that would be an indicator of oil in the coolant Expansion tank - Lots of sludge that settles - will be either rust or soot particles. Rust particles come from a poorly maintained cooling system or one that sat for a while. Big flush will clean a cooling system. Stayed clean for a bit. Expansion tank - Particles coming back. If flush was good then coolant/water should have stayed clean. You used a cooling system cleaner which should have removed all cooling system sludge/rust/etc if performed correctly and it would have stayed clear after that. Seems to point towards exhaust ring leak into coolant. Suspect particles are soot from combustion process. Expansion tank - Test strip for exhaust gasses in coolant. Positive high PH. But you are using tap water with no coolant currently. Distilled water/coolant mix should have a PH of around 8 from memory. What is PH of tap water in your area straight from the tap? Coolant system seems to lose retained pressure - leak somewhere. Nothing visual on radiator or hoses? Nothing showing. Leak could be hidden. Expansion tank - test strip for oil in coolant is negative. Safe to say that oil galley breach of head gasket is not likely given this and other factors like #5, #6, and #7. There may be other pieces of evidence but this is what is sticking in my head. So lets narrow this down - I think you are possibly looking at an exhaust breach of the head gasket into a coolant galley. Its one way pressurizing when engine runs but will reverse when static not running. Apart from checking PH of your tap water, I would run a leak down test on the engine - 2 or 3 times. Do it once then move the cylinder positions by cranking a bit. You want to shift valve positions to ensure a validation. This may or may not work because of how the gasket breach is positioned but its the obvious next step to try. That should point to the cylinder bore which is problematic. Don't worry about the absolute value of the pressure on the leak down, its the consistency thats important.

There are two types of head gasket leak. Coolant galley breaches and Exhaust rings. Test again another two times on the exhaust gasses - a day apart. You are right to be suspicious of a false positive. Coolant strips should still react - they are supposed to react with the presence of oil. That gunk in the coolant is key to the diagnosis as it keeps coming back when it should not. There are only two things it can be but you need to prove which one. Also, please don't look to others and assume you have what they had. Leverage their decision process to diagnosis your problem but don't jump to the end step without going through the intervening steps. You may both have head gaskets fail but the reasons for failure are radically different and so the cure will have some subtle but still critical differences in the rebuild approach. For example a coolant galley breach means I always test for a block that may have gone porous before the rebuild commences.

Interesting. Most people use another D word to describe me. I would not assume that. I bring a major power-to-weight disadvantage to my car. Plus, your driving skills on video show you are much better than the average hacker so I think I have a challenge. Sensational track - loved the layout.

Great video and glad you had a great experience first time out on track with the 620R. Love the circuit - a safer version of the Nurburging. @BruceBe (Beachman Racing) Can I do a shakedown at that track with my car when you finish it this year? Pleassssssse! I want a playdate with Cem's 620R.

I am laughing because the Caterham lot at NJMP have all had this happen at least once to them. Me included. You get towed in. You look baffled. Then a buddy walks up, clicks the roll over button and by magic everything is restored. Glad that was a nice quick resolution of that part of the problem. Good luck with the vibration/loss of power...

It was a Rover 200/400. This was the POS car that donated most of its parts to a Caterham after a ford. If in doubt default to a Rover 200 part search. Tank-radiator expansion - EAP8713 - Genuine MG Rover | Rimmer Bros You saw off the legs. In case you doubt me here is a post from Blatchat - refer post #4 from Roger ("ECR") Freelander Expansion Tank - Dimensions | Lotus Seven Club (lotus7.club) I would also look at post #10 as an option for a different shape expansion tank as you can then use the current round Freelander bottle. I would look for a Rover 200/400/216/416 cap. For the cap, it likely was also used on a Mini. Rover/MG Group made Minis late in the original form's life. Caterham still sell the caps for your car - its on their parts site - but Rimmer Brothers will be cheaper.

Thanks Bruce - will delete it next week.

Vlad - Be careful with that thinking. I suspect you will pull the head and discover the bores are shot to pieces or the block is porous/cracked/warped. Its never ever just a head gasket. Last time I did one, I discovered 4 interestingly shaped pistons...the weird thing was the engine ran just fine.

Vlad - I think your car was originally sourced from Chip Bond. He had a few of those red seats around. No idea why only he had them, never saw them anywhere else.

Ok I assumed you were using a dry-type gauge and it became a wet-type gauge based on how you described it. The wet gauges do go cloudy when the liquid within is contaminated. The liquid is usually a silicone, clear light oil or glycerin - not sure what Marshall use? That happens when the little pressure seal goes "poof" and fuel invades the gauge liquid. I bet it reads low now? At least you are retaining some sense of humor!!!

Some context for the links is always welcomed. By way of background, I am a contributor on the Lotus 7 Club thread you linked. It is old and somewhat out of date as there were later threads with updated knowledge, reflecting off-line discussions which I was a part of, plus a copyrighted article on the L7C site that we are sadly not able to reproduce on here without causing a copyright issue. The majority of the L7C thread is on this forum as we have covered it in the past - I know because I was involved. The Purplemeanie site is a very good one. John is a true enthusiast plus he is an expert in making videos that are educational. He is currently creating technical videos for the Lotus 7 Club. I have provided some back up material to assist. He has an excellent build thread of a Caterham 420R on his site. If you do find something that you think is worthy of interest then please by all means link it via a post but you should introduce it with a short paragraph on why it was interesting and why it is relevant for other forum members here. Otherwise people just get confused as to what you were intending as it creates 'noise' that they have to sift through to find what they really want to read.