free hit
counters
Head Gasket failed again - Engine/Ancilliaries - The Lotus Forums Jump to content
Sign in to follow this  
b041ac1

Head Gasket failed again

Recommended Posts

Right I'm on a real downer, just changed my head gasket and it's lasted 30 miles, the previous one lasted 200miles.

Start at the begining;

I managed to cook the head a few weeks ago (radiator pipe went), so at the same I decided to do a bottom end rebuild as it was also blowing a bit of oil past the rings on hard acceleration.

So after new rings, liners, big ends, a head reskimming and all valves re-cut (by alex carrs - a first class outfit), I managed to do 200 miles before It seemed to pick up a misfire. On checking cylinders 2 & 3 they were down at 60ish psi. No sign of any mayonaise in the oil though, but there was quite a leak from the head gasket underneath the exhaust manifold.

So off with it's head this weekend (getting a dab hand with it now), and another new gasket ordered from SJ's. I checked to see if the head was straight (as a die) before giving everything a good clean, I fitted the new gasket, torqued it to the new procedure, (ie. 15in/lbs, 75degs, 40degs & 5 mins later another 20degs.). Took it out for a spin (didn't go above 2000rpm as I'm still running it in). That was Saturday, took it get some petrol today and I felt the misfire again, behold, mayonaise!!!!!! 30 miles I've done.

What am I missing?

Share this post


Link to post
Share on other sites
Upgrade today to remove Google ads and support TLF.

Before we go any further.

When you did the re-build did you get all the water out of the oil ways? I ask as you didn't have mayonnaise, but do now.

Assuming yes.

Have you checked the liner "nip"? That's going to give symptoms similar to a warped head if it's insufficient.

Was the head checked for damage following the initial over-heat? It could be cracked.

Mayonnaise = water & oil meeting

Low compression = combustion chamber leak.

You seem to have both, which would normally make me think gasket. So assuming it's not that, it has to be something else causing an issue at the joint of head to liners & block, or else you've got two issues, water and oil getting together and combustion chamber leak, in separate places (hence the head damage question).

BTW, do you have new style or old style head studs?

Andy

Share this post


Link to post
Share on other sites

Ah, no I didn't check the oilways, so you're probably right, it may not be a failed head gasket after all, just me being an idiot. Did wonder why I had mayo this time and not the last.

Just checked the compressions and they're all up around 150-160psi, could the misfire be due to me titting with the carbs beforehand and therefore a red herring? It does seem to be idling ok, just jumping a bit when pulling?

fyi, liner nip was 6thou, didn't specifically ask for the head to be crack detected, but wouldn't I have seen something obvious when I had it apart this time?

I have the old style head studs.

Sounds like an engine flush and fresh oil might be a good starter for ten?

Thanks for the advice, really appreciate it.

Tony.

Share this post


Link to post
Share on other sites

Tony,

The rebuild you had done by the workshop did they just rebuild the short block, skim the head and let you have it back, or did you get the complete engine rebuild done by them, If they did the rebuild I would go with Andy on the liner nip been possibilty,

But im assuming that because you removed the head and put a new one back on you did not have a rebuild as you would of took it back under warranty when it failed,

Also did you check the origanal gasket number as if the head had been machined in the past thicker gaskets would of been fiited just a thought of somthing to check, also what about shimming where the valve clearances set properly as this can cause the heat dicipation from the exhaust valves to be near none existant through to lower clearance maybe

I would suggest having the head crack tested and flat tested before going any further also as said check the liner nip

Good luck its a bummer when things like this happen you must have the patients of a saint to keep pulling the head!

Regards danny

Share this post


Link to post
Share on other sites

Hopefully I am reading this correctly.

1. You noticed a misfire and then checked the compression and found two cylinder to be low.

2. Later you checked compression again and found them to be OK?

If the first check was done when engine was HOT and the second when engine was COLD one of two things come to mind. 1.) Valves out of adjustment 2.) Cracked head

You might check valve clearances HOT and COLD. Also pressure check your cooling system.

Good luck and I hope it is a simple fix.

jeff

Oil in water, as mentioned earlier, may or may not be related to your current problem.

Also want to add. Check the air bleed line that runs from the cylinder head outlet pipe to the coolant expansion tank. If this line is clogged you can get an airlock causing the engine to overheat.

Happened on my 83,

Jeff

Share this post


Link to post
Share on other sites

Hi Danny,

I only sent the head away to get machined and the valves re-cut. I fitted the liners, rings, big ends etc.

Didn't check the old gasket, but it looked original (car has done 66k).

Yeah spent a week titting around to get the correct valve gaps, ordering new shims and re-checking and then reordering a couple more because they were still not the correct gaps. When I committed to taking the head off this weekend I re-checked the valve gaps (as I had a passing thought that a bent valve may cause my lack of compression), however all gaps were found to be bob on.

Thanks, if I have to take the head off again I will get it crack detected, I'll take the oil change option first though.

BTW, I have never pulled the engine (what!). Well, I only have a single garage, but I do have a pit. I also have quite a slope on my drive and I live on a hill so if I pushed the car out, I would not get it back in and I could easily see it dissapearing off down the street a a fair rate of knotts, so it makes more sense to me to leave it in situ.

I've done this lot since Christmas, all without removing the block.

Hi Jeff, the initial missfire was before I had the head off a couple of days ago. Compression was down around 60psi on cylinders 2 & 3. This coupled with the leaking head gasket was my reason for pulling the head off and spending all Sunday in my garage ----- again.

So I was pi**ed when I thought I had a similar problem, having done only 30 miles on the new gasket, however the misfire might just have been me over reacting to any noise or querk.

Having being prompted to check the compression this evening, it seems that the compression is still ok, so I think it's simply me being stupid by trying to keep the same oil in until the engine has done the 500miles running in period (now done 250ish).

Thanks Tony.

Share this post


Link to post
Share on other sites

I too had a cylinder head gasket leak right after rebuild so I can sympathize on being extra alert and apprehensive to every odd sound. Year later and I still sometimes "overreact".

Looking good in the pictures.

cheers,

Jeff

Share this post


Link to post
Share on other sites

I'd say you're right with ******g around with carbs causing the mis-fire, and since the water would have got to the oil when you pulled the head, and it's still in there that's the mayonnaise. You will need to flush the oil and use a good mineral oil for a few hundred miles then you can switch back to a synthetic (I assume that's what you're running) once it's started to bed in. That will then flush any mayonnaise out at the same time.

Andy

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  


×