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 Post subject: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Sat Oct 17, 2020 11:59 am 
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Joined: Mon Jun 16, 2008 7:02 pm
Posts: 295
Location: Northern NSW
Need some help on something that I can’t solve with the Mk1.

History: blew a head gasket back in July and repaired it. Serviced the head at the same time (valve grind, seals etc) and dropped in 16 x cleaned lash adjusters to stop the ticking – all went well. I also put in another alternator I had lying around to rid me of some bearing noise.

But, since the job was done there has been this weird issue of the car running slightly roughish for the first 1-2ks including the rpms dropping. Starting is fine – rpm is sweet at idle but then I get the issue above. After a very short time everything is perfect and you wouldn’t know it ever happened and the car runs like a dream, a really good dream!

Trying to solve this has been frustrating. New fuel pump, new ignition coil, new plugs, new coolant temp sensor, all vacuum hoses checked and the switching valves checked for operation, TPS checked, tried a different MAF sensor, different ignition leads, PCV valve swapped over, ECU codes checked, fuel pressure checked, swapped the fuel pressure regulator and fuel pulsation damper over, compression test done, dissy vacuum advance checked, different dissy cap.

I’ve about given up on the problem. One thing I haven’t done is removing the valve cover and checking for crud (from the coolant mixed in the oil during the head gasket blowing) up under that plate that covers the passage of air into the PCV valve as I did at one point have a restriction there when I blew air into the valve cover – it cleared so I didn’t take it further. And, I didn't put the original alternator back on as I can't see that causing it. Oh, and I haven't touched the injectors or the fuel filter which isn't that old.

Any ideas/advice would be greatly appreciated. It’s easy to just let the car run the 1-2 ks to warm up and be done with it but, I’d like to know what causing the problem. Remember, it only happens when the car is cold – once warmed up all is fine. Does that sound familiar to anyone out there?

Cheers,
Rick


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Sun Oct 18, 2020 12:13 pm 
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Joined: Fri Sep 03, 2010 10:41 am
Posts: 1507
Location: Bunya QLD 4055
It is possible you may have a coolant air pocket around the intake plenum which needs bleeding?

_________________
If "X" is an Unknown quantity, and a Spurt is a drip under pressure, then an "EXPERT" is an "Unknown Drip Under Pressure".
Why dont they just call it "Womenapause" instead.


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Mon Oct 19, 2020 8:17 am 
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Joined: Mon Jun 16, 2008 7:02 pm
Posts: 295
Location: Northern NSW
Could you please explain in detail what you are referring too and how you bleed it? There are probably bits of the old head gasket flowing through the coolant but the car runs cool so I didn't think there was a restriction anywhere. I just can't see though how coolant can reduce engine performance/acceleration. In the meantime I'll run a few more checks. We're driving to Lightning Ridge soon and I'm quietly hoping the problem will sort itself out along the way.


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Mon Oct 19, 2020 4:36 pm 
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Joined: Fri Sep 03, 2010 10:41 am
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Location: Bunya QLD 4055
Take off the feed to the CSV, start and run until coolant flows out the tube. Refit the tube and check then.

_________________
If "X" is an Unknown quantity, and a Spurt is a drip under pressure, then an "EXPERT" is an "Unknown Drip Under Pressure".
Why dont they just call it "Womenapause" instead.


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Mon Oct 19, 2020 9:57 pm 
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Joined: Thu Oct 12, 2006 11:58 pm
Posts: 61
Location: quebec/canada
blown head gasket can cause these symptoms,
try to start the car cold for a 5 seconds then stop it and pull out plugs and search for coolant on them,
have similar issue on a customer car , my co-worker did the headgasket and cleaned the old gaske with power tools and score the block head too deep and new gaket would not seal


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Tue Oct 20, 2020 1:10 pm 
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Joined: Mon Jun 16, 2008 7:02 pm
Posts: 295
Location: Northern NSW
CSV is okay with Coolant as that was checked (and bled) long ago, and again yesterday as a precaution.

Re a possible blown head gasket again from a bad HG seal, I did the spark plug test as advised, including cranking the car without them in and no coolant was detected (that was a relief!) Car isn't losing coolant and no bubbles are evident in the radiator so I don't believe I have a bad HG seal. I even used that copper gasket spray over the HG for a better seal.

One thing I didn't mention earlier was the car was sitting around a few days before I removed the head (as I couldn't get one of the studs out). As a result one of the piston cylinders developed surface rust which I carefully removed using 2000 grit wet and dry sand paper. It's possible the compression on that cylinder may have been compromised a little by this and doesn't develop full compression until the cylinder warms and becomes fully lubricated.


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Tue Oct 20, 2020 10:11 pm 
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Joined: Thu Oct 12, 2006 11:58 pm
Posts: 61
Location: quebec/canada
do a compression test cold and hot and see the results will speak
check for injector leakings? when you checked the plugs does one seemed to be more wet then others?? (fuel)
if no obvious results then
for the headgasket thing i suggest, to make sure, if you have a coolant pump to pressure the system and test, let sit with pressure for a long time and re do

do the lifter are fully charged upon a cold start (cause my mk1 dohc tend to misfire cold because valve are ticking hard ) :lol:

i suggest to upload a video of the trouble if possible


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 Post subject: Re: Frustrating issue with the Mk 1 since replacing Head Gasket.
PostPosted: Tue Oct 27, 2020 11:42 am 
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Joined: Mon Jun 16, 2008 7:02 pm
Posts: 295
Location: Northern NSW
Just returned from taking the car and partner to Lightning Ridge, NSW and back and it didn't miss a beat (drove it there and back in one hit @ 8hrs each way) so I don't think I'll worry about that issue anymore with the rev drop. In fact it ran so good you'd hardly believe it was in pieces not long ago!

The little Mk1 created a bit of interest at the 'Ridge' with people asking about it, thinking it was some kind of rally car with the Hella's on the front. The only small drama we had was taking a wrong turn looking for a booked tour and ending up on a clay-based road that the locals avoid during rain. The clay filled and jammed the rear guards and we barely made it back to town as it felt like the handbrake was stuck on. The stuff was a nightmare to get off as it doesn't respond to water pressure so you had to physically dig it out. Oh yeah, we missed the tour by the way!


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