I bought back my old mk5

[JoshB]

That’s awesome work to be fair, and what a legend your mechanic is letting you use his garage!

I’d have been tempted with some new driveshafts though, that rust on them looks out of place now…!

[christii]

Time for a depressing update.

Always wondered why the check engine light didn’t show when the ignition is on. I sort of forgot about it but then I mentioned it to the guys who tuned the car, and they reckoned someone had covered it up. I feared the worst, but surely nobody would actually do that?? Well it turns out, yes they do, the previous owner is officially a c**t.
The car had a bunch of misfire fault codes when i first gave it a once over after buying it, which I cleared. And since there was no check engine light, I never thought about the codes ever again. Also, I’ve changed all the spark plugs, coil packs and the cars had a full service.
Well I decided to take the speedo out to see if I could find why the light wasn’t coming on. I can’t believe what I found!


















As you can see from the pictures. After removing the tape, the check engine was on!!

Codes are the same as when I first bought it. P0300 - 0304.
Also when the plugs where changed, the plug in cylinder 1 was badly corroded and it looked liked water had got inside.

This led me to wonder if it was the head gasket. So I bought a test kit from Amazon.

If the blue liquid turns yellow, I’m in trouble. And guess what….







So now the car is going to the mechanics on Monday for a full diagnosis. He says he would be surprised to see a gasket go on one of these engines. But the test I used has good reviews, and it would explain the corroded plug. Plus, why would someone go through all the trouble of covering up the engine light unless it was a big job to fix.

Gutted.

[Clarkj93]

I've never come across a head gasket going on these, it's super rare. Do you have the infamous generic milky oil cap by any chance?

But yeah, who ever taped that up is a right see you next Tuesday.

[christii]

I've never come across a head gasket going on these, it's super rare. Do you have the infamous generic milky oil cap by any chance?

But yeah, who ever taped that up is a right see you next Tuesday.

Nope, no milky oil cap. Though the oil consumption is a lot. I guess I’ll know more once the mechanic does his diagnosis.

[LC5F]

That is really is $hitty news - it may have only blown into a waterway and not got to the oil.

A minor win - at least they only taped over the LED, I have seen older cars where the bulb had been smashed.
Where was it last MOT'd - they are meant to actively check for both CEL and ABS lights coming on with ignition.

[christii]

That is really is $hitty news - it may have only blown into a waterway and not got to the oil.

A minor win - at least they only taped over the LED, I have seen older cars where the bulb had been smashed.
Where was it last MOT'd - they are meant to actively check for both CEL and ABS lights coming on with ignition.

Yeah it sucks. I’m based in Northern Ireland. Our MOT is different than the rest of the UK, it’s the government who MOT our cars so there’s no way it slipped through. Although I’m not 100% sure if a check engine is a failure or not? But the car was MOT’d just before I bought it.

[JoshB]

Christ on a bike… as if they taped over the check engine light?!
How big a job is it to get the clocks out? You’ve got me worried now as I had a 1840(I think) code the other day which supposed to bring up the CEL but didn’t on mine…!

[bobby_fodge]

I've seen the exact same thing on a mk4 someone I knew bought from a trader.

[christii]

Ok so apparently it’s definitely not a head gasket.
Mechanic isn’t 100% sure but he thinks it’s an ECU issue. Also he noticed that the car backfires loads when you rev to 3500 rpm, only at stand still, not when driving. The whole car shakes when it’s backfiring!
I phoned Autotune, they assure me it’s not the map and if it was the ECU they would of spotted it. Though I’ve gone ahead and bought another ECU to try, and it’s booked into Autotune again on Tuesday so they can have a look to see if it is the map. Though I’m pretty sure the problem was there before the map, hence the cover-up job.
Anyone any ideas?

[JoshB]

Are you losing coolant? White smoke from the exhaust?
You need to try and figure out where the exhaust gasses are getting into the cooling system first.
It could be a sensor issue if the misfire counter is just rocketing up.

[christii]

Result!!

It was the ECU! Autotune transferred the map onto the new ECU and no more engine light.
The car is driving better as well. No more stutter, and before it was pooping and banging a lot. I thought it was the map but it’s doing it far less now.

 

[JoshB]

Phew, that’s good news!

No more combustion gases in the coolant then either?

[christii]

Phew, that’s good news!

No more combustion gases in the coolant then either?

Yeah the Amazon Gasket test is bugging me. Though the mechanic said he tested the coolant and it was fine. And since there’s now no symptoms of a problem with the gasket I have to hope it was just a false positive.
There’s loads of the blue liquid left. I might use the test kit again and maybe check a couple of other cars to see if they get negative results.

[Mekaniko]

happy to hear that now is working fine! Congratulations for the investigation + conlcusions!

[LC5F]

That is good news - but how does that explain the head gasket tester going yellow?