Reliant Scimitar overheating.

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History
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Reliant Scimitar overheating.

#1 Post by History » Thu Jun 18, 2015 7:05 pm

Is there any Scimitar experts.

The engine 3 litre V6 Essex, gradually over heats. It has new Radiator and thermostat.

In the dim and distant past. I recall something about bad airflow in the engine compartment. And the cure being holes in the inner wings.

Apart from overheating its quite a nice car.

Bob

rich.
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Re: Reliant Scimitar overheating.

#2 Post by rich. » Thu Jun 18, 2015 8:20 pm

can you fit an electric fan?

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JPB
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Re: Reliant Scimitar overheating.

#3 Post by JPB » Thu Jun 18, 2015 8:28 pm

Scimitarweb is full with people who have specialised knowledge of the things. :thumbs:
rich. wrote:can you fit an electric fan?
I fitted one of those and it made no difference to my last Scimitar's likelihood of overheating. Maybe I should have put it in the car rather than the bathroom ceiling?
J
"Home is where you park it", so the saying goes. That may yet come true.. :oops:

History
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Re: Reliant Scimitar overheating.

#4 Post by History » Thu Jun 18, 2015 8:33 pm

The engine driven fan should be ok. When a car is moving the air coming in the front at say 30mph is probably a fair bit more than a fan can pump. At idle the engine doesnt over heat. At a 60mph it guadually overheats 30 miles.

I won't do anything until I find correct solution because the owner has had a radiator and stat fitted and it the same. Naturally he's not impressed by the other mechanic. Its all too easy to spend money not solve the problem. I can't waste the guys money thats not nice.

Still at least the cars ok for Short journeys.

Bob

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JPB
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Re: Reliant Scimitar overheating.

#5 Post by JPB » Thu Jun 18, 2015 9:20 pm

There is a school of thought that has the fixed fan causing an obstruction to airflow at cruising speed since its blades are effectively a solid disc at speed, so trying an electric fan would probably help if the engine driven fan were removed first. I take it you've flushed the block and heater thoroughly and checked that the water pump isn't one intended for a Granada. Also, check that the HGs are the correct ones for the year of the engine. Some gaskets we've seen have actually blocked off some of the coolant passages from the water jacket in and out of the heads.
J
"Home is where you park it", so the saying goes. That may yet come true.. :oops:

History
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Re: Reliant Scimitar overheating.

#6 Post by History » Thu Jun 18, 2015 10:20 pm

I have also heard that fixed engine fans can at speed become an obstruction. And an electric fan will windmill.

I could remove the fixed fan and run at 60mph with no fan at all.

Don Pither I believe designed a front spoiler. I want to find out if this helps air flow through the rad.

I am cautious with cars that are known for overheating. The engine was used in other vehicles that don't overheat so why the Scimitar.

60mph is not fast and the engine should happily run at this speed. They reckon cruising at 60mph is about 30 bhp worth of power and 30 bhp worth of heat to get rid of. Surely the cooling system should easily cope.

On the web the general opinion seems to be careful maintenance of the cooling system. To me this points to a marginal system. But which bit is marginal. The rad looks big enough for a 150 bhp engine.

I don't want to do this job unless I can definitely cure the problem. The customer will only get annoyed.

Bob

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TerryG
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Re: Reliant Scimitar overheating.

#7 Post by TerryG » Thu Jun 18, 2015 10:35 pm

It's not something really daft like a sticking stat is it? the bypass may be enough to cool it at idle but not when load increases.
No idea if it's an issue with the scimitar but with my RR the A/C radiator had fallen apart (corrosion but not leaking) and was stopping air flowing through it so stopping it getting to the water radiator. I had the engine rad re-cored and then bought a new one before noticing :S
Understeer: when you hit the wall with the front of the car.
Oversteer: when you hit the wall with the back of the car.
Horsepower: how fast you hit the wall.
Torque: how far you take the wall with you.

History
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Re: Reliant Scimitar overheating.

#8 Post by History » Thu Jun 18, 2015 11:41 pm

I did wonder if the water pump impellor had fallen off. But that will cause overheat quite fast. Also is the water pulley the correct size. Old cars have had plenty of time for mix and match parts replacement. Esp a Ford engine.

On inspection the engine compartment is clean and tidy and no suspect anything. The idle is smooth and quiet. The car goes about right for 150 bhp car of that weight. Quiet a pleasant car to be in. I wouldn't mind a Scimitar myself. Not quiet an estate car so has useful load space.

It appears that the air enters the rad from under the bumper. If it is an airflow problem then it's starting to go beyond my technical knowledge.

I am wary because I foolishly got involved in a Stag doing the same. Only to realise the actual design was wrong. Same old Leyland story, another flawed gem. Hart Racing sorted the problem out --- eventually. They must have spent thousands. I leave the Heroics to others. I don't mind the time but I can't just give parts away if I can't fix it.

I like my cooling systems to have lots of reserve cooling capacity and be robust and not fussy.

Bob

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JPB
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Re: Reliant Scimitar overheating.

#9 Post by JPB » Fri Jun 19, 2015 8:46 am

Plenty of Scimitars run just fine without unintended holes all over the inner wings or the front end. Try a larger water pump pulley to slow the flow down sufficiently to eliminate the cavitation that had been starving the pump, this has worked and completely solved the overheating trouble on a couple of local ROC members' cars.
Some respond to an inline header tank in place of the expansion vessel fitted as standard, though this can - in cases where the waterways don't match - mask the symptom (local overheating) rather than curing the problem (dirt in the water jacket because of the conditions in which the engines were kept prior to assembly). To establish whether this is a problem with your car, try running over at least ten miles or so of mixed conditions with the pressure cap on the first notch in the neck of the bottle, rather than the end one. Or substitute a 4Lb cap for the 15Lb one for the same purpose, this will still prevent boiling at below </>110 C assuming the correct volume of coolant, speaking of which don't use OAT in this or any other mixed metal cooling system. And the Dagenham models in particular - but the Cologne ones also - work well with MPG coolant which has the bonus of being safe for animals.

Send him our way if you're not up to the stress of it all. ;)
J
"Home is where you park it", so the saying goes. That may yet come true.. :oops:

Classic Microcars
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Re: Reliant Scimitar overheating.

#10 Post by Classic Microcars » Fri Jun 19, 2015 11:20 am

JPB wrote:Scimitarweb is full with people who have specialised knowledge of the things. :thumbs:
Bump!

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