Hot running and misfire - cool rad hot head

[Mrmci]

Hi all,

I'm in my first year of ownership, having bought my Elan Sprint from the estate of a chap who sadly died. I'm finding the little problems which were probably on the to do list.

The Elan runs beautifully with the temp gauge at about 85c, when moving, but as soon as traffic slows or I have prolonged motorway cruising, the temp gauge climbs to 90c and up to 95c when stationary or in crawling traffic. Ive put in a re-cored 3 row radiator, flushed and replaced the coolant, new 85c thermostat, new hoses and SPAL fan with an 85c thermal switch but for some reason the rad is only switching on at 95c head temperature. Using an infrared pyrometer I can see that the top of the rad is indeed 85c but the head is 95c.

Once the temp starts getting above 90c the engine starts stuttering, particularly when setting off from a standstill, getting better with revs. As it gets hotter this gets worse. I've never seen above 95c on the gauge.

Any ideas on potential things to check.

Help appreciated,

Cheers

Mark

[rgh0]

Everything appears to be working but you have an excessive teperature drop from the head to the where the fan sensor is. Is the system actually full of coolant or is the fan switch sitting in an air pocket ? Can you get a lower temperature or adjustable fan switch to fine tune when the fan cuts in

cheers
Rohan

[661]

Do you know which plugs you are using?

[Mrmci]

Yes the coolant is definitely full and I can manually switch the fan on so I can kind of work around the problem but it still gets super hot in stop start traffic. It also has a slight miss at motorway speeds where the fan would make no difference.

[rgh0]

If you really have a 10 C temperature drop from your head ( which I presume you are meausring with the car temp guage) and the radiator inlet ( which you are measuring with a IR gun) then you must have a very low coolant flow at idle for it to cool that much over such a short distance of pipe. Potentially a sticking thermostat or a pump that is corroded or a collapsed hose inner lining

Alternatively there is some error in your measurments. IR gun read low typically and the error varies with the surface emissivity. The in car gauge can be checked by immersing the bulb in a pot of boiling water

[miked]

Mark,
May i ask about how you know the system us full. The Elan can be problematic with the low postion off the radiator in relation to the engine. As Rohan points out air can be present. I assume you are aware of the correct operation of the recuperation system. The two way valve arrangment in the rad cap that allows pressure to relieve into the recouperator bottle. Then the vaccum valve that allows coolant to be pulled back as the engine cools. Even with the level in the neck top of the cap you can fill the system further providing you have enough coolant in the bottle. After a run this allows the cooling engine to draw it back without pulling air. I have found with about 3 heating and cooling cycles I can add another 2 to 3 pints. It keeps empiting the bottle!
So it is important that the pipe from the bottle is not leaking air. Also that the pipe in the bottle is near to the bottom with a slant cut. In fluid.
For the above reason i have run with a small alloy tank and cap in the top hose. Or one of those thermostat housing with the cap instead of the standard arrangement. Dummy cap fitted to rad in both circumstances.
Mike

[cliveyboy]

Mark
Sounds like all the problems I had with my Sprint when I first bought it.
I assume as you have a 3 core radiator that you are still using the original smaller radiator with side panels.
I do know of people who use the smaller rad and say they don't have overheating issues. But I have found them to be marginal at best.
Also an electric fan on the front of a small rad takes up a lot of space and acts as a big restriction for air flow.
All my issues were solved with an earlier S3 full width radiator and thermostat housing with a filler cap. I have run it in 30C heat and never overheats.
In stationary traffic the temp rises but the electric fans cuts in and temp goes back down.
A full width radiator is money well spent.
Clive

[Mrmci]

Ok,

Yes I'm measuring the top of the radiator/top hose with an IR gun. I'm also using an IR gun on the back of the temperature sensor, which seems to confirm the sensor reading.

My car doesn't run an expansion tank. Just an overflow pipe off the top of the radiator to ground. Whenever I open the cap the radiator appears brimmed so that's my assumption for no air in the system. I do know the problem described as I've had this happen to me on a motorbike, where the radiator cap allows air to be sucked back into the system.

I've completely refreshed the cooling system with new hoses, new upgrade (standard, narrow sprint style) radiator, fan and new style thermal switch.

As an aside I've also had the carbs ultrasonically cleaned and rebuilt with new gaskets, so I'm pretty sure it's not got an air leak, causing it to run hot.

I'm starting to conclude my car runs hot for some reason, I guess all that is left is.

The water pump
Silted up block
Insufficient cooling area on the radiator. I'm inclined to rule this out for the time being as the car also gets as hot with the heating on and the system has just been refreshed with no apparent difference in performance.

Annoyingly I think I may have to do the water pump, I think if I'm going to the effort I'll upgrade to a Burton, cartridge style pump.

I'll search the forum for this but any tips from anyone? I guess I may as well take the engine out to check for the block being silted up.

Cheers for the help,

Mark

[miked]

I would fit an expansion bottle and get your pipe in there. Nothing lost. Also check cap has centre vac valve. In my opinion the systems don’t fill properly because of the low radiator. When squashing the top hose with your hand you can hear it. Plus it has a small effect on the rad level.
When I have pulled core plugs on twin cam blocks the rear one is usually worst progressively followed moving forward. Rear have been full. Next half way up.

[2cams70]

Are you an advanced user of the temperature guage?

[Mrmci]

I'm not sure what makes one an advanced user, so I'd say "no I'm not"

However, as the car starts misbehaving as it gets hotter it would seem to imply that the temperature is increasing. It does also correlate well to both my IR pyrometer and FLIR thermal camera too.

[2cams70]

I'm not sure what makes one an advanced user, so I'd say "no I'm not"

However, as the car starts misbehaving as it gets hotter it would seem to imply that the temperature is increasing. It does also correlate well to both my IR pyrometer and FLIR thermal camera too.

Quoting directly from the Ford Escort workshop manual for both the regular pushrod engine and the Lotus Twin Cam engine we have the following:

Thermostat: Starts to open 85C to 89C, Fully open 99C to 102C
The radiator pressure cap rating is 13 PSI which suggests a water temperature (use of water not coolant as the worst case) of 120C before the radiator actually boils and you start to loose coolant.

I'd suggest what you are observing is perfectly normal. If during regular running on road you were consistently seeing temperatures of 100C it may be a cause for further investigation (and especially so if the engine had a previous history of running lower temperatures under the same conditions). If however only on some limited occasions (eg. idling in traffic, long uphill pulls, etc.) you were seeing occasionally temperature excursions a little over 100C I wouldn't be too concerned.

The engine is designed to operate over a temperature range and not to a specific figure.

[mbell]

All my issues were solved with an earlier S3 full width radiator and thermostat housing with a filler cap. I have run it in 30C heat and never overheats.

I have the same setup from Clive on my car. I ran it in temp approaching 40C with out issues and fan cycled on/off at idle. Keeping temp within range.

I would fit an expansion bottle and get your pipe in there

I agree with this. Coolant expands when warm and contracts when cooling. If you don't have functioning recuperating system the top hose will have air in it when cold, as it will push coolant out when hot and suck air back in when cooling.

The real question is why a few degrees engine temp makes such a difference to how the engine runs? It shouldn't have major running issues at 95C IMO, so you could be trying to treat a symptom rather than the real issue.

So I would be taking careful look at carbs and ignition systems and seeing if there is anything to fix there rather than trying to micro manage the engine temp to avoid the running issues.

[Mrmci]

Thanks chaps, great comments and input. You are right it could well be normal and the poor running may well be something else.

I've replaced the cap, rotor arm, leads, plugs, points have been swapped to magnetic system but I am still on the original coil from when I bought it.

The problem does "feel" fuel related. If you blip the throttle at tickover, when it's hot it definitely stutters. Not really knowing what it feels like could it be a fuel vaporisation type problem?

I'm on a mechanical fuel pump with a new fuel line if it make any difference?

[mbell]

Have you checked the plug colours? Checked fuel pressure? What plugs have you fitted? Did you re-time the engine after fitting electronic ignition? What carbs do you have fitted?