norfolkluego
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| posted on 22/6/08 at 06:34 PM |
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Overheating
Guy's,
You helped me out with a couple of questions about an overheating 1600 Crossflow last week. But now having had a good poke about today it would appear
all is OK with the cooling system, water pump is fine, rad is heating up evenly, no cool spots so I'm a bit stumped (and the engine is really
running HOT).
Is it possible we've just leaned out the fuel mixture too much, I know lean mixtures burm hotter than rich mixtures but could that really cause
a severe overheat. We've recently replaced the downdraught Weber with a pair of Dellorto DHLA 40s (and a new manifold) which should be jetted
correctly for a 1600, I say should because I haven't had it to pieces to check the sizes of the jets. Any help would be appreciated becaused
I'm getting a bit stumped.
John
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britishtrident
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| posted on 22/6/08 at 06:38 PM |
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Excessively retarded ignition will cause severe overheating. Check the static timing and that the ignition centrifugal advance is working.
[Edited on 22/6/08 by britishtrident]
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ed_crouch
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| posted on 22/6/08 at 06:46 PM |
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If the jet numbering is the same as DCOEs, have a look at the jetting and put the jet sizes up here. I've got a 1700 Xflow on twin 40 DCOEs, and
the mains are something like 140, idles about 45F9 IIRC. Thats on 33mm chokes.
Also, you mention that you have recently put the carbs on...
What are you doing for a fuel pump? You probably will want a facet silvertop or the like, and you'll definitely want a Malpassi Filterking on
the bulkhead to regulate the fuel pressure. About 3PSI is normally plenty if the filterking is level with the float chambers.
Sounds like a daft question, but how do you know its overheating?!? OK - so if it boils up - fair cop, but if the gauge just reads high, it could be
an inaccurate gauge. If you're running Smiths classic gauges, you need to run the temperature gauge off a 10 volt regulator, or it'll
overread (if you run it straight off 14.4 volts).
Hope this helps you home in on the issue. get back to us if not!
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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norfolkluego
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| posted on 22/6/08 at 06:49 PM |
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This engine has a Burton A2 cam and a modified head (polished ports and slightly bigger valves) and the advice the engine guy gave me was ......
Ignition timing to be run with no vacuum advance due to excessive overlap from camshaft. Timing to be set to static as per standard engine, then
advance until detonation just heard at full throttle through the rev range then back off two degrees.
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norfolkluego
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| posted on 22/6/08 at 06:56 PM |
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Car has a facet fuel pump and a new filter/regulator set to 3 psi but it's mounted probly about 4 inches below the float chambers.
Jet sizes I was told I was given (and as I say I've not checked yet) are
140 main
210 air correctors
f16 emulsion tubes
4.5 auxillary
45 F8 idle
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r1_pete
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| posted on 22/6/08 at 07:00 PM |
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Assuming you rad is big enough.
Is the system full, are you sure there are no air locks.
Is the pressure cap the highest point on the system? if it isnt the system will find a level somewhere below the cap, this will cause only partial
filling of the head and subsequent overheating.
On a crossflow the thermostat housing is one of the best places for the pressure cap, fiesta's had a suitable housing.
[Edited on 22/6/08 by r1_pete]
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norfolkluego
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| posted on 22/6/08 at 07:15 PM |
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The gauge is reading hot but that's not what really worried me it was that the bonnet was too hot to touch.
Pressure cap is on the thermostat housing and the rad is a modified Capri one that fills the available space in the front of the Velocity. The only
other thing that springs to mind is that there's no expansion bottle so when the engines cold the water level looks low but looks OK when hot.
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r1_pete
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| posted on 22/6/08 at 08:23 PM |
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Is your head gasket ok?
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norfolkluego
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| posted on 22/6/08 at 08:29 PM |
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Head gasket should be OK (unless the overheating has damaged it but I've only run it for short periods since it started). the engine's
only done a couple of hundred miles from a complete bottom end up rebuild.
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rusty nuts
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| posted on 22/6/08 at 08:38 PM |
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The advance mechanism in the distributor can sieze and cause the timing to be retarded at anything over idle . I use a Rover header tank with a Fiesta
thermostat housing that has a bleeder pipe connecting to the header tank which bleeds any air from system . An expansion tank is totally different and
is not as efficient.
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norfolkluego
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| posted on 22/6/08 at 08:48 PM |
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If it's any help, the engine runs really well when first driven (apart from a little popping from one carb but I haven't balanced them
properly yet) but after 10-15 minutes it starts to misfire a high revs and when you check it the inlet manifold is really, really hot, I was assuming
the misfire was connected with this somehow.
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02GF74
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| posted on 22/6/08 at 10:21 PM |
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you need to get a strobe to see what the timing is and if it changes with rpm.
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DavidM
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| posted on 22/6/08 at 10:27 PM |
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Have you checked the colour of your spark plugs? That'll give you an idea if the timing or fuelling are far out. They should have a light brown
deposit on them.
My money would still be on it being an airlock. Try squeezing the bottom hose several times in quick succession. I find this pumps quite a lot of air
out of mine when it is freshly filled with water.
David
Proportion is Everything
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miserableoldgit
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| posted on 22/6/08 at 10:38 PM |
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Overheating Xflow
Check on your nosecone, I found it was easier on mine for the air to travel around the rad rather than through it. Cured with a bit of aluminium and
rubber strips and the situation was much better
Youth and vitality are wasted on the young
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andyharding
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| posted on 23/6/08 at 08:21 AM |
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How hot do you call running hot (in degrees C)?
Are you a Mac user or a retard?
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rusty nuts
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| posted on 23/6/08 at 05:21 PM |
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If the inlet manifold is too hot it sounds like an air lock ? Do you have a bi-pass hose fitted between the manifold and the water pump?
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norfolkluego
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| posted on 23/6/08 at 08:26 PM |
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Temp gauge says 140 and I'm inclined to think it probably is.
Yes, bypass hose is fitted.
Quite taken with the idea of fondling the bottom hoses, sounds like a pleasant way to pass half an hour!
I'm coming round to the air lock I thinks, as I said as there's no expansion tank the water level looks quite low when cold bit the volume
rises very quickly as it warms up, quite probably air expanding rather than water, it really does expand quickly (and we did lose a lot of coolant and
refilled when we changed the manifold/bypass hose so quite possibly some air trapped in there.
As usual lots of great ideas, thanks for the help, I'll post an update when I get to the bottom of it.
John
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David Jenkins
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| posted on 23/6/08 at 09:01 PM |
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Maybe it would help if I describe my 'anti-lock' technique.
The setup: My x-flow has the bypass hose, but no heater. The thermostat has a small hole drilled in the base-plate. The filler cap is the type that
goes over the thermostat, with a small hose off to the overflow tank.
Filling from empty:
1. pour about half of the coolant in slowly. Wait for the bubbles to come out of the hole in the 'stat.
2. Firmly squeeze the hose that goes from the base of the rad to the water pump. You'll see the water-level surge in the filler hole, and more
bubbles appearing. Keep squeezing until no more bubbles appear.
3. Continue to fill the system in small steps of around 500 - 750ml (it's the size of my plastic jug!). After each fill, more squeezing until
all the bubbles go away.
4. Top up to the brim, put the cap on, half-fill the overflow tank.
5. Run the engine at tick-over until hot, keeping an eye on the overflow tank - I expect the level to rise by up to 25mm (no more).
HTH,
David
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stevebubs
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| posted on 23/6/08 at 09:34 PM |
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Try changing the static timing and see if it helps...you can always change it back....
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britishtrident
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| posted on 29/6/08 at 11:06 AM |
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quote:
Originally posted by norfolkluego
Temp gauge says 140 and I'm inclined to think it probably is.
Yes, bypass hose is fitted.
Quite taken with the idea of fondling the bottom hoses, sounds like a pleasant way to pass half an hour!
I'm coming round to the air lock I thinks, as I said as there's no expansion tank the water level looks quite low when cold bit the volume
rises very quickly as it warms up, quite probably air expanding rather than water, it really does expand quickly (and we did lose a lot of coolant and
refilled when we changed the manifold/bypass hose so quite possibly some air trapped in there.
As usual lots of great ideas, thanks for the help, I'll post an update when I get to the bottom of it.
John
140 F or 140 C ? --- big very difference and neither can be correct.
140c would into the superheat range, at the sort of pressures your cooling system runs.
Normally depending on the pressure cap cooling system run at between 7 and 15 psi (ie 1.5 to 2 bar absolute) that gives a boiling point of 115c to
126c.
so 140c is not possible.
140F means the engine is running cold 60c.
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norfolkluego
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| posted on 3/7/08 at 06:32 PM |
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Update to all the above.
It seems it was an airlock after all. Fitted the water pump as I'd already bought it and it seemed rude not to, the water that came out when the
old one was removed was filthy. So, new pump fitted, filled system with decent coolant, let it run for a bit the raised the front of the car a little.
Massaged the hoses as recommended and a fair bit of air did come out. Engine now sweet, no overheating and no puking out of coolant as it warms up.
Great job, thanks guys.
John
PS Now if I could only work out why the brake warning light has suddenly come on!
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David Jenkins
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| posted on 3/7/08 at 06:56 PM |
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Good news! 
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