Lotus Elan

Hot rough running

PostPost by: terryp » Tue Feb 05, 2008 4:32 pm

Hello
Now I've sorted out my starting problems I'm trying to use the car as much as possible. One thing I've noticed is the car seems to run really well when warming up all the way to about 80 degrees. (I have a 78degree thermostat) Then the temperature goes above this to around 85 to 90 degrees where the engine begins to run rough almost sluggish . The fan starts at this temperature.I also get some smoke from the exhaust that I don't get normally. Set up is : -
Dellorto Carbs tuned with Manermeter and CO2 meter (reading 4%)
BPR7ES Plugs (although I'm trying some BPR6ES at the moment)
New Coil, rotor arm , condenser , plug leads , caps , points
Engine was rebuilt by previous owner.
Anyone with any ideas ???????Should I try to get the fan to come on earlier to keep it cool??
Thanks
Terry
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PostPost by: carrierdave » Tue Feb 05, 2008 5:37 pm

Have you checked the water level in the radiator? It sounds as though you may have a leaking head gasket. :oops:
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PostPost by: terryp » Tue Feb 05, 2008 5:53 pm

Thanks for such a quick reply , I've just been out and the antifreeze level in the radiator is fine

Terry
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PostPost by: ppnelan » Tue Feb 05, 2008 9:35 pm

terryp wrote:...although I'm trying some BPR6ES at the moment...

Perhaps this is a clue? Maybe you need to try a colder plug...
Smoky exhaust could indicate flooding?

:arrow: Matthew
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PostPost by: 1964 S1 » Tue Feb 05, 2008 10:22 pm

I'm a Weber guy, I'd check the chokes.
Are they all opening completely?
Did the previous owner drive it after the rebuild?
Now I'm thinking you should check the timing chain marks too. One cam could be one tooth off.
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PostPost by: twincamman » Wed Feb 06, 2008 3:36 am

perhaps a head gasket ----ed
dont close your eyes --you will miss the crash
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PostPost by: terryp » Wed Feb 06, 2008 8:19 am

The problem was also with the BRP7ES plugs , I was trying the BRP6ES to try and cure the problem which it didn't
The car did about 2000 miles after the rebuild (according to the MOT certs)
The smoke is not white so the carbs could be flooding, although I did change the needle valves and adjust, but I did use non original valves bought on eBay. Would Viton valves be better ?

Terry
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PostPost by: mikealdren » Wed Feb 06, 2008 8:27 am

Terry,
If I'm teaching you to suck eggs, apologies in advance!

The engine runing temperature is generally maintained by the cooling system and the thermostat maintains it at the opening temperature. If it rises above this, the cooling system is not removing heat as fast as the engine is generating it so either the engine is producing too much heat or the cooling system is not removing the heat (or a combination of both). With an older car, I would usually suspect the cooling system first, especially as your car is running well at normal temp.

Firstly, are you running the car stationary during warm up. If so, there is no airflow through the rad so it will continue to heat up until the fan cuts in.
If you are driving the car, it seems that there there is not enough airflow through the rad without the fan, this may be a blocked rad matrix. Other possibilities for bad cooling performance include:
Radiator cap (but yours seems ok)
Blocked waterways (anywhere but the rad is always a prime suspect.) If your car has been standing for a long time or not cleaned out for some time, it may be worth getting the system flushed.
Kinked hoses.
An airlock in the cooling system, the heater matrix is usually a suspect - is the heater working well, if so it's probably full of water not air?

If the cooling system is all ok, look elsewhere but the Elan cooling was not over specified and always needed to be 100%. Would I alter the thermostat or fan? No, sort out the root cause.

Good luck
Mike
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PostPost by: terryp » Wed Feb 06, 2008 8:49 am

Mike
Thanks alot , thats basically my train of though but being quite inexperienced with twin cams I'm a bit nervous. The rad looks very old so may be a good place to start.
Basically the fault came yesterday after about 10 minutes of driving , which I would imagine the thernostat would have kicked in before this , which makes the radiator answer even more likely.
Why the small amount of dark smoke? unburnt fuel ?
Thanks
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PostPost by: mikealdren » Wed Feb 06, 2008 10:15 am

If the temp stabilised for a while at the correct temp, that suggests the thermostat is opening, if it wasn't the temp would simply continue to rise until it boiled.

However, although 'stats are are supposed to fail open but they don't always! It is possible that the thermostat isn't opening fully, you can always try running without a thermostat to see if it's the problem, if the car still overheats, you have elimimated the thermostat. If it's now ok, replace the 'stat.

Smoke etc may be from running too hot, I would sort the cooling out first.

Still sounds like the system isn't disipating enough heat and I would tend to suspect the rad.

Mike.
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PostPost by: Robbie693 » Wed Feb 06, 2008 10:25 am

I Have exactly the same symptoms - and it's my head gasket as far as I can tell.

The cooling system has been flushed multiple times - runs clean now.

Fitted new plugs, heater is hot so no air lock.

Biggest giveaway is the water leak from the back of the head and the bubbling in the radiator.

Taking it apart next week to fit a new gasket, rebuild the heater, re-bush the steering column, add relays to my headlights, refurbish a pair of alloys and give it a service. No doubt plenty of posts to come...
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PostPost by: Tonyw » Wed Feb 06, 2008 1:28 pm

Guy's,
A quick way to see if the radiator is blocked is simply take of the rad cap, drain enough coolant so you can see the tubes, if you can see ten tubes and three have crud in them you can assume you radiator is 30% blocked.

Muddy water goes real hard when left for while to dry out, you can get bits floating around your cooling system after re-filling and then getting jammed in the radiator cooling tubes, If the engine is to be laid up for a long while it is sometimes better to flush out the system and store it dry. FWIW.

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PostPost by: terryp » Wed Feb 06, 2008 1:36 pm

Now everyone has got me completely paranoid that the head gasket has gone.
I've just taken the car out again, aacording to the temperature gauge ......
ran fine up to and maintened around the 80 mark (on the thermostat) then going up a few hills and with engine under load the temperature went up above the 85 mark car was still OK (starts to run rough at 90 on the gauge)
Got home and gently removed the rad cap to which some antifreeze obviously left the car. Started the car with the rad cap off and it did bubble and surge a bit but I think that this was the force of the water circuit.
There is no mayonaise in the oil filler cap and I'm not loosing any antifreeze.
HELP !
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PostPost by: worzel » Wed Feb 06, 2008 3:32 pm

Hi Terry

Before you dive in-

Are you actually losing water?- if not cannot be head gasket

What exactly do you mean by running rough- ie is it running on 3 cylinders, misfiring etc. when the problem occurs try using insulated pliers and pull off one lead at a time to see if this makes any difference. If say pulling off three (one at a time) causes the revs to drop and when you pull the 4th there is no difference you've at least pinpointed part of the cause.

If this occurs do a compression test and see if there are any discrepancies.

Check for air leaks at the servo/headlamp vacuum pick up points.

Alternatively, next time try pulling out the choke- the problem might be fuel starvation- although your reporting that it's ok whilst warming up doesn't suggest this fault.

Basically what I'm suggesting is try the simplest tests first before expecting the worst.

Regards

John
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PostPost by: kstrutt11 » Wed Feb 06, 2008 3:35 pm

Terry,

To check it for the head gasket place the overflow tube from the radiator in a clear bottle of coolant (old coke bottle works), if gas bubbles out once the engine has warmed and is at operating temperature you have a failed head gasket, or worse still cracked /porus head, if not it is probably a blocked radiator.

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