Reliant Scimitar overheating.

[mr rusty]

Basics first, is it actually, really, overheating, grinding to a halt in a cloud of steam, or is the only evidence what the gauge says?.....I.e., if it didn't have a temp gauge, would you still think it was overheating?

[TerryG]

That's a good point, have you tested the voltage regulator to make sure it is outputting 10v even when the engine revs are as they would be if you were cruising at 60?

[JPB]

Oh it'll be overheating alright, but only after a few miles when the cavitation sets in. If it's been driven like that for any length of time, then take it out on a test drive and have a sniffer handy to test the header tank for exhaust fumes once the symptoms show.
One of the local ROC guys had this happen on his way to a show last weekend, he'd been rebuilding the engine over the winter and hadn't used the car between times. That engine never once ran hot under any conditions during the 170,000 miles it achieved before he decided to take it apart. He's about to discover the difference between a generic Essex water pump and the correct one - the hard way.

[History]

I got the owner to show me the service history of the car snd the new radiator is a second hand radiator. So I took the rad out and it felt heavy. A sign of scale in the rad.

The rad shop is going to re core it with super gill high efficiency core. They phoned later to confirm that the rad has poor flow. This as someone has said will cause cavitation. Cavation is bad news because it seriously lowers the pumps ability to pump. Also they are going to put a boss in the radiator end tank for a thermal switch. I brought from a mate a BMW electric fan. I also brought from Ford a fiesta themal switch and a 30 amp relay.

The engine driven fan has been removed. The water pump
pulley is smaller than the crank pulley.

The rad shop said that the Scimitar suffers not from overheating but from people who insist on not using antifreeze. Which scales up the rad tubes.

I am now confident that the overheating will be cured. And the owners getting value for money.

Cavation can also damage the the impellor.


Bob

[rich.]

i was under the impression that an educated chap like you had checked all the simple things like that first... still you have fixed it

[History]

I was told that the rad was new. Not a nicely painted used one. This threw my line of thinking. Then I got side tracked into air flow problems. Which turned out to be unfounded. Us grease monkeys are prone to getting complicated.
As I said I don't do a car unless I know exactly whats wrong. In this case 30 mins of spanner work and I have the problem cracked. I should think by the time I have mounted the fan, relay and rad etc etc that total time will about 4 hours. So not to bad. The V6 Essex is a robust engine even if it can get a bit vocal.

Bob

[tractorman]

Cavitation also causes erosion - as some 60's Ford tractor owners found to their cost when the cylinbder blocks became porous! Never underestimate the power of boiling water (or water at high pressure): things like stainless steel steam pipes need careful planning and swept bends (not elbows) as steam could erode the steel on a sharp bend, with the potential of some very nasty consequences!

IIRC, the main problem with the Stags was that people didn't follow the instructions for coolant - and head tightening etc. It wasn't all about needing high capacity/efficiency radiators and "export" fans! I seem to think that was mentioned in both Wheeler Dealers and For the Love of Cars!

[Cambronne]

Yet another Scim brewing up...had my share of this. It sounds fixed but here are some more pointers for future reference.

* It the used new rad was as original, it was a dual crossflow. This means it had two 'lower edges' to silt up. This makes a good case for anticorrosion/antifreeze mix in the system.

* I found that a Kenlowe fan flailing in the breeze wasn't a great solution. Dual fans that could be fixed to the rad were better.

* After my time (with Scims), I understand a Citroën BX electric fan was the fix of choice.

* Loads of hopefuls would cut holes behind the grille in the hope of enhancing airflow. This simply a way of cooling down the spare wheel.

Finally, keep an eye on the health of the head gaskets, they are the next weakest link.

[History]

I heard of a big diesel left idling for a week due to a busted starter. Cavation caused no 1 cylinder liner to collaspe and hydraulic the cylinder, which wreaked the engine.

HP steam is very powerful and very dangerous. They use steam in New York. Sometimes man hole cover get blown up.

Cavation of boat propellers is an issue that mariners are always aware of. It wastes fuel big time and pock marks the blades and can damage the transmission. The propeller blades get eroded around the edges and bits can break off. Not good.

In my imagination the low pressure caused by cavation is trying to stretch the water. Water is not compressible or stretchable. To stretch it has to turn to a gas - steam. The steam then condenses very fast. This is sort of like lots of little explosions.

Cambronne.
Thanks for the heads up on the Scimitar overheating. I will be fitting the system with antifreeze. I will also do a sniff test and check torque on head bolts. Plus oil and filter change. I might as well check the valve clearances and plugs and points. I do the testing on plain water once I am happy I stick 50% antifreeze in.

Bob

[JPB]

Regarding the concentration of additive; 50% is too much. At that sort of ratio, the MPG/MEG will effectively reduce the ability of the water in the coolant to conduct heat away from and to protect the iron. It's a common misconception that more is always better but 33% will offer more than adequate protection against corrosion and keep it all running at far lower ambient temperatures than we ever see, even here. Also, I'd be fitting a larger pulley to the pump, it's best to have it running at or slightly below crank speed to avoid cavitation so if the pulley is smaller, this can exacerbate the problem, fit one that's intended for an AC 3000ME, Land Rover Ford V6 kit or whichever is the easiest current source. I have a couple that I turned from aluminium which are offset to compensate for the extra depth at the hub and place the V correctly, one is off to Switzerland and the other is available to ROC members at the cost of the time plus the metal.
The ideal way forward is with EWP kits that vary the speed of the impeller to suit load, these aren't that much dearer than suitable, new mechanical pumps, very few of which are genuinely split new these days in any case and many of these older castings are already eroded but will be used regardless.