Temp Switches

[Jensen]

Is the Temperature switch form a 1.4 motor compatible to the Red Warning light on the dash of an R10? Or is it a sort of progressive switch (not sure what else to call it) that is for a guage? ie it would make the light get brighter and brighter as temp increases similar to the green generator light?

The R10 switch seems to be one that bolts to the head rather than in it, Altgough does it require the bolt that holds it on to be in contact with the coolant in the head?

thanks

Jensen

 

[JohnW]

Is the Temperature switch form a 1.4 motor compatible to the Red Warning light on the dash of an R10? Or is it a sort of progressive switch (not sure what else to call it) that is for a guage? ie it would make the light get brighter and brighter as temp increases similar to the green generator light?

The R10 switch seems to be one that bolts to the head rather than in it, Altgough does it require the bolt that holds it on to be in contact with the coolant in the head?

thanks

Jensen

Jensen,

I think you'll find it is a simple switch. When the temperature of the device exceeds its pre-set limit, the contacts close and the light comes on by earth return through the switch.

The bolt doesn't need to be in touch with the coolant. This switch, neatly I reckon, is a sensor for cylinder head temperature. So if the coolant is lost, the temperature warning light still works. Much better than many other systems. And more use than a worry meter (sorry, temperature gauge) that you might not notice creeping up.

Our R8 has both, with a long-ago fitted VDO gauge with sensor in the top hose, and the light switch on the head.

Cheers

JohnW

 

[JohnW]

Is the Temperature switch form a 1.4 motor compatible to the Red Warning light on the dash of an R10? Or is it a sort of progressive switch (not sure what else to call it) that is for a guage? ie it would make the light get brighter and brighter as temp increases similar to the green generator light?

The R10 switch seems to be one that bolts to the head rather than in it, Altgough does it require the bolt that holds it on to be in contact with the coolant in the head?

thanks

Jensen

Jensen,

Sorry, I might have answered that the wrong way around - the 1.4 "switch" is presumably a sender unit that feeds a progressively higher voltage to the temp guage as the temperature rises.

I doubt that it would give a progressively brighter glow to a lamp as it probably is a low current device that needs the resistance of the gauge itself to operate properly. If anyone knows better, I'll be interested to hear.

Cheers

JohnW

 

[Jensen]

Thanks JohnW,

So can i bolt the R10 switch onto the 1.4 head (I assume both motors run at similar sort of temps) and hook it up to the Warning light. And then hook up the 1.4 sender unit in the back of the head to the VDO Temp gauge i am going to put in?

At the moment i have the Sender unit connected to the the Warning light and occasionally, maybe 3 times in the 2 weeks that the 1.4 has been in the car, the warning light has had a slight glow (very dim). It was definetly from the Temp unit not the oil pressure as i unplugged the wire of the temp sender and the glow went out. The car seems to be running slightly warm but im hoping its just in need of a new thermostat and the radiator flushed out ( In a rush gettin the motor in i didnt have a new thermostat on hand so used the one that was in the hose attached to the differnet radiator screen i put in from the donor car). The motor is pretty hi-comp with a cam so maybe that is the cause of it seeming warmer in the engine compartment? An eletric fan on the outside of the radiator might add extra cooling? The custom screen i put in has brackets that appear to be for that purpose.

Jensen

 

[JohnW]

Thanks JohnW,

So can i bolt the R10 switch onto the 1.4 head (I assume both motors run at similar sort of temps) and hook it up to the Warning light. And then hook up the 1.4 sender unit in the back of the head to the VDO Temp gauge i am going to put in?

At the moment i have the Sender unit connected to the the Warning light and occasionally, maybe 3 times in the 2 weeks that the 1.4 has been in the car, the warning light has had a slight glow (very dim). The car seems to be running slightly warm but im hoping its just in need of a new thermostat and the radiator flushed out The motor is pretty hi-comp with a cam so maybe that is the cause of it seeming warmer in the engine compartment? An eletric fan on the outside of the radiator might add extra cooling?
Jensen

Jensen,

Mixture of yes and no and don't know! I presume we're talking a warmed 1.4 in an R10 or R8 here.

The temp switch for the R10 warning light can be bolted onto the head and connected to the wiring for the light.

The sender unit may (or may not, probably not) be appropriate for the VDO temp gauge. If it is a Virage temp gauge and a Virage sender unit, you may be OK. If not, heaven knows.

These cars control temperature pretty well provided (and I mean PROVIDED) that a few things are right:

1. undertrays are correctly in place
2. the seal between the radiator panel and the engine compartment lid is in good condition
3. radiator, water pump, thermostat etc are all in good nick.

I'd expect an electric fan (presumably blowing forwards through the radiator from the chamber behind it) to be of limited use except for driving in heavy traffic. When the car is being driven at reasonable speed, i.e. 40 kph +, there is a good airflow forwards through the radiator, this air then reversing and going out the back underneath the radiator mounting panel. The only time in 30 years that we have ever had even the beginning of an overheating issue with our R8, regardless of ambient temperature, was carrying large loads on a roof rack and disturbing the airflow at the rear of the car, where it goes down through the grill at the back of the engine compartment lid.

Normally, despite the thermostat, our R8 runs cool.

Hope that helps.

JohnW

 

[Jensen]

Thanks for your help JohnW,

Yes its a warm 1.4 in the back of a R10. At present it is running without undertray on the exhaust side as it was waiting to go to the exhaust shop to get a hot dog fitted. For the last year it has been running sonic extractors and a 30cm straight through muffler so as you can imagine it was slightly on the noisy side (ie could hardly hear my mobile phone when travelling on freeway!). With the warm 1.4 it was even louder so now it has a baffled hot dog running along the back of the car as well( much quiter and seems to go alot harder, more torque and much smoother than the previous exhaust set up). Prob is that the hot dog may disturb the air exiting the engine bay. Didnt the 8G rally cars (Group 2 or something) have a exhaust along the back of car? did they have to do something to overcome the prob or was it not an issue?

Anyway i have a week of uni so ill refit the undertray, new thermostat and flush the coolant system. It also has a custom radiator screen that is sort of in 2 pieces in which the top piece can be removed to allow better access to the engine bay. Ill post a pic soon. I didnt realise the seal was so critical so ill fit a rubber strip to seal against the boot lid. Hopefully it should run a little cooler after all this. Ill report back once its done.

Jensen

 

[renault8&10]

Jensen,

John's answers are correct:

The R8 switch is exactly that as John described. The 1.4 sender unit is also exactly that. I have mine hooked up to a VDO gauge and it works fine (my hotted up car runs at 80C no matter what the ambient). It is a warmed 1.4L in an R10 (40DCOE Weber etc). It had a fully rebuilt radiator put in it - these can and do block if not used for a long time or if only used for short trips and have been known to cause grief.

My R8 runs the original switch on the head.

I would try running the standard switch to the warning light on the 1.4L head and run a wire to the temp gauge you have from the sender unit you have at the back of the head.

The rest of John's response is also VERY Important. The undertrays are important - if you have taken them off to run a custom exhaust; that will make the car run 5-10C hotter, as will the other things John mentioned re sealing the radiator panel to the bootlid. If you don't have the trays fitted either put them back on (even if you have to modify the exhaust side) or expect to run a little hotter. My R10 currently doesn't have them (R12 exhaust header causes fouling) so if everthing else is in good order you can run without them; but it is better if you don't.

The original idea was that the trays and bootlid seal formed an area of low pressure under the car which attracted air in through the vents on the bootlid and hence through the radiator. I have also found that removing the radiator surround "Shroud" (that encloses the fan) on the inside can also cause overheating.

It sounds like you may have several minor causes conspiring to cause your overheating. Best to systematically check each component and test until you have it solved. Best of luck.
KEvin.

 

[renault8&10]

Obviously I was still typing my response while you were doing yours as you have answered some of my queries/suggestions.

One other point - In my opinion and experience; thermostats don't fail in the sense that they increase the temperature in which they open; they either open at the right temp (78C or whatever) or they fail to open at all leading to overheating fairly quickly. Therefore, a faulty thermo will make the car run hot; but not just slightly warmer. Others may have more experience than me, but that is what I have found.

 

[JohnW]

Jensen,

John's answers are correct:

KEvin.

Kevin,

I'm glad you agree!! These airflow matters are all important and it isn't obvious/intuitive. I forgot to mention the shroud. We carried a double bed mattress on a roof rack at 100 kph once in warm weather, and it's the only time I ever have seen the temperature gauge on my car move even above the low part of the "normal" range.

Regarding the R8G exhausts: they were a lateral muffler on some, and I guess there was enough space around them to avoid airflow restrictions.

JohnW

 

[Jensen]

well it's been two weeks since i put the engine trays back on, sealed the compartment with a new rubber strip and gave the system a good flush and the R10's now running back at a normal temp. Thanks for help JohnW and kevin, amazing how much of a difference those few little things made. I retensioned the head yesterday as it's now travelled the 1000km. now i can take it for a really good drive and see how she goes.

Cheers

Jensen

 

[JohnW]

well it's been two weeks since i put the engine trays back on, sealed the compartment with a new rubber strip and gave the system a good flush and the R10's now running back at a normal temp. Thanks for help JohnW and kevin, amazing how much of a difference those few little things made. I retensioned the head yesterday as it's now travelled the 1000km. now i can take it for a really good drive and see how she goes.

Cheers

Jensen

Terrific result! I'm pleased that the details were the issue. I've heard of older cars fitted with big engines that had huge difficulties, even going to the extent of 2 radiators. The ones I know of were all fixed with the correct shrouding and sealing for airflow reasons.

Enjoy the drive! Oh, and thanks for letting us know.

JohnW