Drinking Coolant / Head Gasket

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xDParis64

xDParis64

Well-Known Member
Posts
266
Location
Fareham
Hey!

As per usual I am having issues, at this point I work on this car for mechanical experience and not for the economic value 😂 Though recently the engine has been drinking coolant so I think it's going to need a HG so I ran a compression test... 175psi on all cylinders, It could be that my cheap tester is mis-calibrated but they all read the same...

So I thought fine! Let's stick the bore-scope down in the cylinder and while I couldn't get perfect pictures, I did see something strange:
1746299139618.png

Now please bare with but I am sure you can see the gaps where the valves would go but also a light ring. This goes around the WHOLE piston on all four cylinders I thought it was oil from around the rings, but it is not the edge? It's overlapping the valve dips
My thinking is if the head gasket has failed spectacularly then the head would sink down and the piston would impact the bottom of the head causing this ring? Or could be from a previous HG replacement where it was skimmed too much? None-the-less the pistons did NOT look clean so I don't know where all this coolant is going, I cannot find any leaks, it must be in the combustion chamber right? We will find out eventually, but thought I would put here to gauge opinions and experience first! Most confusing bit is the compression readings...

Thank you!
 
There appears to be reflections but looks like your arrowed part of gasket to me. Is that looking up at head underside or block ??
 
That's looking down at the piston through the spark plug hole, that is the piston itself. Inlet manifold can let water in? as in just water like rain and puddles or coolant? I replaced the gasket when replacing the engine so it should be okay but maybe it got caught somewhere?
 
I'd say that what you can see and think are valve cut outs are the shadows or actual valves standing open looking like they overlap the bright ring. The bright ring could be the top piston ring if these are the actual valves rather than cut outs.

The inlet manifold can allow water to be ingested by the engine through the inlet ports so it would not necessarily be visible.

Google 'K series inlet leak'. Caterham group have a write up and a modified gasket is available apparently.
 
As Andy said, the shiny ring is the top ring visible in the gap between the piston and bore.
If there's no coolant connection in the oil, then it's unlikely to be a HG. If the inlet manifold seal is allowing coolant past, then it's likely to go out the exhaust, rather than into the oil.
 
Nodge68 said:
As Andy said, the shiny ring is the top ring visible in the gap between the piston and bore.
If there's no coolant connection in the oil, then it's unlikely to be a HG. If the inlet manifold seal is allowing coolant past, then it's likely to go out the exhaust, rather than into the oil.
Click to expand...
You'll have to forgive my innocence and stupidity, how does the inlet let coolant in? Does a coolant jacket / coolant galley run past/ through the inlet manifold? But even then, in my brain it would enter the combustion chamber and steam clean the pistons? Maybe it's best i take the manifold off and see what i see 😅
 
In the plastic inlet manifold on the left hand side [as you look at the motor] there is a jiggle valve - a small diameter pipe leaves the manifold by the engine oil dipstick and connects to the coolant tank. The plastic manifold can warp... or be very slightly mis-shaped and coolant can get past the 'O' ring style gasket and get into the cylinders... see my pic

I set that gasket in with a smear of suitable sealant aroundd that small 'loop'. At the other 'end' there is another loop with a coolant aperture in the head. It goes nowhere and seems to be redundant so I thread that hole and screw in an allen key plug to seal it up.
 

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xDParis64 said:
You'll have to forgive my innocence and stupidity, how does the inlet let coolant in? Does a coolant jacket / coolant galley run past/ through the inlet manifold? But even then, in my brain it would enter the combustion chamber and steam clean the pistons? Maybe it's best i take the manifold off and see what i see 😅
Click to expand...
Yes, the rear head coolant bleed passes through the manifold, simply because the manifold is in the way. The seal of the manifold fails in time, allowing the coolant to enter cylinder No 1 while the engine is running, because the manifold is under vacuum.
This coolant gets burned or actually vapourised as it passes through the engine and into the exhaust. In bad cases, coolant can be smelled at the tail pipe.
 
Thank you both, really helpful! that means I am to replace the gasket and O2 Sensor coming soon, I will be sure to update here on the news, I should imagine then to replace the gasket the coolant needs to come out?
 
Well I for once have good news, means I'm a bit of a moron, but that isn't new information.

I was removing the inlet manifold today when I noticed a stud was without a nut.... I asked if someone had taken it off to a resounding... no... That's right I have 6/7 nuts holding on the inlet manifold, which wouldn't have really caused an issue but the bolt missing? (Highlighted in this pictures) Feel free to guess before looking :p
1746461976832.png

YUP.

Probably one of the single most important nuts holding on the inlet manifold was missing, if it had been one in the middle or something I probably never would have noticed. Safe to say this has likely caused this issue I won't mark it solved yet as I need more time to confirm if it has been resolved, but with a quick (slow) warm to operating temp and then cool down to ambient and back to operating and back down, the coolant has not changed level and is holding strong!

Thank you for the help all! Glad I did not need to rebuild the engine because I missed a nut!
 
Just a quick update on this one, I don't think (fingers crossed) it is still losing coolant, however, I think in the time it was, it has inadvertently fried the O2 Sensor? Would that be possible with enough Coolant going through the exhaust? (On this model I have only the 1 O2 sensor on the headers)

I've just bought a Pscan unit anyway so will be able to test and a spare o2 Sensor on standby but no emissions tester so wouldn't be able to confirm if it changes anything unless the O2 Sensor is so obviously broken. It has a very slight misfire during idle that you can't feel or anything but you can hear it kinda pop / choke out of the end of the exhaust but perfectly fine when driving?

Any thoughts and suggestions would be great! Thank you all
 
Hopefully you have the coolant leak sorted but if still loosing a little, they also commonly loose coolant at the water pump so look out for leaks there.
 
Alibro said:
Hopefully you have the coolant leak sorted but if still loosing a little, they also commonly loose coolant at the water pump so look out for leaks there.
Click to expand...
I will keep an eye out! That will show up in the oil right? Maybe about time I do an oil change actually 🤔
 
So didn't get a chance to look at the water pump, however, Managed to plug in my Pscan to log the current O2 sensor.

As explained to me by @pscan.eu the O2 sensor should fluctuate between 0.2V and 0.9V Where 0.44V is a missing / wiring fault and 0.2/0.9 is lean and rich

I logged the data and plotted it on a graph (my missus did this because I can't)
1751714210332.png

I have marked some concerns on the same image but below;
1751714304186.png


They are numbered so I hope someone can provide some clarity

1. It doesn't seem like it fully "Fluctuates properly, where instead of a sinewave it is trying to drop but prematurely goes back up shown as little valleys between peaks.

2. I was under the impression it should fluctuate between 0.9 and 0.2 but sometimes it is dropping as low as 0.06 or 0.1

3. It looks like the voltage has "shifted" down as it almost never reaches 0.9 but that may be normal, I the redlines indicate the 0.9V and 0.2V markers

This was performed with the engine warm and up to temperature, I have a new O2 Sensor here and will be fitting this today and testing again, so I will get some new readings on the new sensor. If anyone has any epiphanies while I fit this new sensor, please do let me know !

Thank you!
 
Looks about right to me. It's more important that the O2s switch between high and low regularly, rather than the exact value reached each switching cycle.
 
So I replaced the O2 Sensor to ensure that was not it, and nope... It is still misfiring... I don't THINK it is consuming coolant since replacing that bolt/nut properly on the intake but super confused what could be making it misfire / failing the emissions... I would think it could be consuming oil but the oil level has not changed or at least doesn't seem like it... Here is a video of the misfire;



If anyone has any other ideas to fix this?...
 
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