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Section : Engine
Engine, cooling system, fuel system, exhaust system.
Posted By : Mark Wessendorff, 05-Apr-2005,
11:06am
I bought a 1967 Mk1 GT6 in May last year. I love the car and have had great days driving it and just tinkering with it on my drive. I do have a few
problems though and include all of them in this message as they may be related! One problem I had from the start and never managed to sort out was the
heater would not blow hot air. I tried the following recommended cures, flushed out radiator and coolant system using rad flush, flushed out heater matrix,
changed the thermostat, checked heater valve was opening OK, burped the system to ensure no air locks, I found the heater return pipe was blocked but even
after clearing that I still never got warm air which made the winter months a bit chilly! One thing that I always found a bit strange was that where the
two hoses (that go to and from the car heater matrix) joined the engine by connecting to the 3 way banjo bolt (3rd connection was to the heater return
pipe) when I ran the engine and disconnected either of the pipes that run to or from the heater matrix I noticed the coolant was being pushed with equal
force into the heater matrix in both directions! Was this the reason why the coolant was not flowing through the matrix? Surely the water would need to be
at a greater force one way than the other to get the water to flow through the heater matrix? Any advice on this would be most appreciated.
Over the last year I have lived without a warm heater. This weekend I fitted an Aldon Ignitor electronic ignition and was tinkering away checking the
timing with a strobe as I was getting an occasional misfire and total lack of power when I got over 3000rpm (like the car was only firing on 3 cylinders).
I checked my fuel supply, oil in the carb pots and needles moving OK. I noticed to my horror bubbles of water appearing along the cylinder head gasket. The
leak had caused a rusty stain on the engine bulk head so the blown gasket must have been around for sometime and this explained why I needed to top up the
radiator every few weeks. The bubbles could only been seen if you revved the engine over 3-4000rpm. I was not getting any oil in the water or vice
versa.
Anyway, I took the plunge and removed the cylinder head to replace the gasket. As I now have the engine in bits I would like to take advantage of the
situation and would appreciate any advice on what else I should do other than just replacing the head gasket. Here is a list of things I am considering
which I hope will improve things sort out my other heater problems.
Definite: new gaskets, new thermostat, radiator cap – anything I should do / check with the engine
Considering : getting the cylinder head skimmed, new banjo bolt (if I can get the old one off!!), water pump (any way I can check whether the old one is
working OK).
Thanks
Mark
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Posted By : Colin Wake, 05-Apr-2005,
04:12pm
Whatever you do, DON'T try to remove the banjo bolt. BTDT, got the kit-form manifold in the garage!
I think you may have had the heater plumbed up wrong.
Make sure the return pipe under the manifold is clear as well as it's entry into the back of the water pump housing.
Colin
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Posted By : David Rumens,
05-Apr-2005, 06:21pm
I fully back Colin recommendations "not to touch the banjo bolt" as this will just shear off leaving you with a useless stub!
Once it gets to that stage you have to weld a bolt to the remaining stub and then use a socket with heat and oil to to remove it. It can take
ages.
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Posted By : Mark Wessendorff,
05-Apr-2005, 09:17pm
Many thanks for your advice on the banjo bolt. My experience in car mechanics is limited. How could the heater be plumbed wrong it's only got
an in and an out!? Is it possible the previous owner could fit it upside down or wrong way round?
I have cleaned up the top of the engine block tonight but worried it isn't clean enough. How clinically clean do I need to get this block ready
for the gasket? It has areas of discolouration. Should I worry about scoring the surface if i put a circular wire brush attached to a
drill?
Thanks
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Posted By : Colin Lindsay,
05-Apr-2005, 10:04pm
DON'T WIRE BRUSH IT!! You want to keep the faces as flat and score free as possible. As long as there are no gouges or scores which will
cause leaks between the cylinders and oil / waterways just wipe the top down with petrol on a clean rag and fit the new gasket. Make sure
the top of the block face is free from dirt, fibres or the like which would prevent a good seal and torque the head down in the correct
sequence or at least middle to outside.
I know you've tried a lot of remedies but it sounds like your heater matrix is probably seriously blocked or restricted; this is the reason
water appears to flow in both directions depending on which pipe you disconnect; the 'in' pipe when disconnected allows water to flow
normally; the 'out' when disconnected allows the water to flow more freely than the heater matrix so instead of water exiting from the
matrix pipe it takes the path of least resistance ie out of the system backwards. There might be a solid item eg dried sludge causing the
blockage but too tightly stuck to come out under flushing.
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Posted By : Mark Wessendorff,
05-Apr-2005, 10:23pm
Colin
Thanks for your advice. I did wire brush the cylinder head but I am yaking it to a specailist tomorrow to check over and scim if
necessary. My concern now is the small amount of wire brushing I have done tonight to the top of the block. There are areas where there
are very light scratch marks. I could post a photo tomorrow if it would help in knowing whether I need to skim the top block as well -
if that possible?
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Posted By : Mark
Wessendorff, 05-Apr-2005, 10:34pm
The wire brush I have been using isn't a heavy duty one but more of a small softer type similar to a suede shoe brush - I am still
worried though that I may have really goofed by using one. I read in last months Practical Classic Mag on an article about
rebuilding a Triumph 6 cylinder nd they had wire brushes all over it - maybe that is because they were skimming it all afterwards?
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Posted By : Colin
Lindsay, 05-Apr-2005, 11:28pm
Possibly.... it's okay on the outside of the block and as long as you haven't made huge digs or scores in the metal top you
should be alright. Even using a metal razor-blade type scraper should remove any debris but check the block face using a metal
straight edge before refitting the head. There were a number of glaring errors in the PC article anyway so don't depend on it.
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Posted By : Mark
Wessendorff, 06-Apr-2005, 07:42am
Thanks Colin. I will check it over as you have adviced and keep my fingers crossed. Went to bed with a heavy heart last
night after all the work only to possibly have made things worse - little knowledge dangerous thing and all that. I did
have multiple nightmares last night all about this **** head gasket. Woken up this morning more tired than when I went to
bed and none of this emotional trauma is mentioned in the Haynes manual!! It's worrying to hear these mag articles often
have errors in them!
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Posted By : Mark
Wessendorff, 06-Apr-2005, 09:52am
I have a few of light scratch marks on the top of the engine block from my wire brush work. If you run your fingr nail
across them you can not feel them they are that light however is there a recommended way to take them out. A friend at
work has suggested using grinding paste? Any advice on this would be very much appreciated. Thansk
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Posted By : Mark Wessendorff, 06-Apr-2005, 10:58am
Does anyone know whether gasket manufacturers offer special "problem solving" head gaskets for a GT6 that have a
high incidence of head gasket failure. These gaskets are often made of high heat materials such as graphite and
have other special features such as additional combustion chamber armor, added sealing beads, more thickness,
etc.
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Posted By : Nathan Gabbott, 06-Apr-2005, 11:16am
I would recommend getting a Payen head gasket, they are still available new, and much better quality than the
rubbish some suppliers tout. They appear to have updated the design with modern materials for even better
performance, so your in with a good chance of it holding out.
Try a few auto factors, I found one in Leamington that could supply next day, and it cost no more that a cheap
one from a specialist.
nathan
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Posted By : Chris Taylor, 06-Apr-2005, 02:45pm
Originally you asked the question as to what other work to do at the same time as the head was off. It
rather depends on what state the rest of the engine is in.
Unless everything in the head looks pretty new, it might make sense to get new valve guides, new springs
and exhaust valves (it's only ever the exhausts that deterioriate with age and use)or, depending on how
much you use the car, consider a lead-free head.
At the very least you should decoke the head and passages, and regrind the valves. Personally, having once
had a spring break and drop a valve (no, miraculously it did NOT fall in and damage the piston!) I would
always replace the valve springs with good quality new ones unless you can be sure of the existing ones
history.
If you do end up taking the block out of the car to take to your specialist for checking, then it opens up
a whole new range of possibilities;
IF you can get them (currently some supply problems I think for Mk1 engines) I would consider replacing the
crank bearing shells with the same size as currently fitted unless you know the mileage the current crank
has done. If you have the sump off, just replacing the crank thrust washers (not expensive, and you only
have to remove the rearmost bearing cap) might be prudent. The oil pump is also easy to change at this
stage if there is any doubt about its condition. Again, unless it is pretty new, it's worth thinking about
changing at least the clutch driven plate while the engine is out. I'd better shut up now or you'll be
frightened by how much you COULD spend.
If for any reason the pistons have to come out (eg to skim the block face) then discuss with your engine
specialist whether the bores need honing and new rings fitting.
I can't remember all the details around the three way adaptor held on by the infamous banjo bolt, but I
seem to recall that there is a small bleed drilling somewhere which is meant to influence the "strength" of
flow in one direction. It is also possible to connect the wrong hose to the wrong connection.
While a blocked matrix seems the most likely cause, it is worth checking for blockages and obstructions
(including any elderly rubber hoses which can collapse internally) THROUGHOUT the coolant circuit. Once the
engine is at temperature, the temperature of the inlet and outlet hoses will help to determine if hot water
is reaching the matrix, and any hot or cold spots on the matrix itself will indicate any blockages. It may
sound like teaching grandmother to suck eggs, but there is precious little natural airflow through the
heater from the car's motion so you will feel little warmth unless the blower is turned on and the flap
valves are sending air to the right places.
As the job is easy to do (and parts readily available) I'd leave the water pump alone. Unless the bearings
feel "gritty" or "rumbly" or there is any sign of leakage, you cannot predict failure very well. Just wait
till water starts hissing out of it and then replace it. Might be next week but more likely to be some
years!
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Posted By : Mark Wessendorff, 06-Apr-2005, 04:20pm
Thanks for all your advice. As I have struggled with the basics up until now I am not as keen as I was
at the beginning of this message to do lots of other things to it now I have the cylinder head off! I
am lacking experience and confidence at the moment!
I took the cylinder head to Guildford Autos at lunch time today and arranged for it to be skimmed just
to be sure. I asked their advice on ensuring the top of the engine block is good. Checking with a
straight rule and feeler gauge. He also recommended wrapping emery paper round a flat hand file and
lightly running it across the block. Does this idea sound OK and what grade of paper should I use?
Chris - your comments on the banjo bolt were interesting with there being something to influence the
force of flow in each direction. That is what I thought could be part of the problem with my heater
hence the desire to get it off and replace.
Regards
Mark
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Posted By : Don Cook, 07-Apr-2005, 02:52pm
I'm in a similar dilemma to you Mark. I'm about to get my head off and I'm not sure where to stop.
I'm going to decoke, replace guides and have a bit of a gas flow (removing ridges and polishing up
the ports). Do I fit new piston rings...big end shells...where does it end? One thing I'm confident
about is that our engines are forgiving and you can be confident in your current ability, after all
you at least got the head off! We all started where you are now!
Get yourself a good manual and be guided by that and welcome to the world of oil, grazes, swearing,
frustration, highs and lows...the list goes on.
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Posted By : Mark Wessendorff, 07-Apr-2005,
09:17pm
I went to Guildford Autos and got a Payen Gasket but looking at it tonight it's exactly
symetrical so it can go either way up but it does not tell me which way is up! Does it matter
which way up the gasket is fitted? HELP!
Don - Thanks for your message. I could have got a garage to sort out my head gasket and though
I never got a quote I'm sure it would have been a fair amount of dosh but when I bought the car
last year I knew that is not what it's about. Owning an old classic that gets poorly, working
on the car yourself and (hopefully!) getting it back on the road tip top is where the greatest
pleasure and satisfaction of owning such a car is all about and going through sweat and tears
gets you there!
I spoke to Canley Classic today about should I get an unleaded head, replace valves and springs
and was adviced that if I was not burning oil (which I am not) just leave the valves alone so I
am just planning to get the gasket in and back on the road.