Strange coolant temps

jimbob · Post by **jimbob** » Thu Jul 14, 2011 6:18 am

Hi,

I've been seeing some cray running temps, normal running is fine 88 - 90c at a steady 100km's, in an ambient of 33c - 37c, when the ambient lifts from 37c - 44c coolant temp is anywhere between 90c - 94c fans pull's in and lowers it down to 90c.

When its idling anything from 92c through 98c, its like the fans not pulling enough air through the rad in idle traffic, or is my water pump on its way out, buy not circulating enough coolant?

The mix i have in at present is 30% coolant with the rest as distilled water.

Fitted a new stat LR Oem 88c, carried out several back flush's, with block / rad cleaner, power washed the rad core / A/C condenser as well.

Any ideas will be great.

Cheers

Jim

ChrisJC · Post by **ChrisJC** » Thu Jul 14, 2011 6:57 am

Is the idle speed normal? (i.e. 700-ish)

Chris.

Post by **katanaman** » Thu Jul 14, 2011 7:12 am

I take it this is a new problem and its been ok in these conditions before? Check the radiator core is ok and hasnt started falling apart. Maybe back flush the radiator in case it is silting up and the obvious one check the fan to make sure it is actually performing fully. It may be slowing down with age. Check mixture as well, if its starting to run weaker it will be hotter.

jimbob · Post by **jimbob** » Thu Jul 14, 2011 6:03 pm

Hi,

Thanks very much for the replies!!

I've checked the engine rpm tonight its around 725 rpm, with the A/C on, the radiator is around 18months old, so should be OK?

Timing is 4deg BTDC as per the spec for a non catted Disco.

I've removed the sagging LR bonnet cover this evening and fitted some dynaliner bonnet insulation, so will give the air a smooth passage over the block, plus I've removed one of the rubber seals on the bulk head to aid the expelling of the hot air from the lump.

Its a newish problem, in April i did a top end overhaul new cam / head gaskets, replaced the condenser etc

The engine flush i used was a Forte brand, left in for around 35- 60 mins as i could'nt drop it out hot.

DaveEFI · Post by **DaveEFI** » Thu Jul 14, 2011 6:28 pm

Does this only happen with the AC on? The AC condenser chucks out a lot of heat. I'd say approaching 100 isn't unusual at idle with the AC on.

jimbob · Post by **jimbob** » Sat Jul 16, 2011 8:00 am

Hi,

Been running more tests and with the removed rear bonnet seal, it looks like a more stable temp.

Ran with the A/C for 5 km's as long as i could with the heat, and it dropped a couple of deg's, left it to idle for 5 mins, and i could feel more of a draw of warm air out of the back of the bonnet.

I'm putting it down to the new condenser being more efficient in removing the heat, from the cabin, thus dumping it in front of the rad.

I was going to drop in some W/water to reduce the surface tension of the water.

Jim

jimbob · Post by **jimbob** » Sun Jul 24, 2011 11:43 am

Looks like i am getting nearer the issue.

The Discovery has a rear A/C unit, happen to switch it off, and the temp dropped around 2c stable at 93c or there about's, with the front still running.

Because the engine is just ticking over the fan is not pulling a huge chunk of air through the rad, i could fit a 16' electric fan by cutting in to the cowling and set it to come on @ 93c, to aid in drawing more air through the core.

Or could i get hold of a heavy duty fan clutch, does one exist?

on a side note what is the critical temp on a standard rover V8 I've heard some many different numbers 110, 112 etc.

On whom is the best outfit to go too for a bespoke ALU radiator in the UK?

Thanks,

Jim

ramon alban · Post by **ramon alban** » Sun Jul 24, 2011 12:33 pm

jimbob wrote:Because the engine is just ticking over the fan is not pulling a huge chunk of air through the rad,

Hello Jim,

Sounds to me like the viscous fan unit is not engaging when the radiator gets very hot, because at tick-over (say 800rpm) when the fan engages you will definitely notice a dramatic increase in air flow and a roar from the fast moving airflow over the blades of the fan.

At 800 rpm that fan moves a lot of air.

I suggest you read these two articles on the viscous fan, and how to test it,

http://www.vintagemodelairplane.com/pag ... ous01.html

also how it must behave during the heating/cooling cycle.

http://www.vintagemodelairplane.com/pag ... ing01.html

Most of what is written there can be applied directly to your RV8 cooling system.

Regarding the change in temperature when the rear A/C is switched on - that is exactly what one would expect, simply because of the extra engine load, which generates more heat which in turn is NOT being extracted by your (probably) duff viscous fan.

Regarding critical temp - I would think 110 would be about right, but you really do not want to be there.

Read this for some insight into what is best,

http://www.vintagemodelairplane.com/pag ... emp01.html

jimbob · Post by **jimbob** » Tue Jul 26, 2011 10:55 am

Hi Ramon,

Thanks for the links some very good reading!!!

As you have stated the fan's does sound like its going south, I'm going to get a spare ordered.

Have you ever used water wetter or similar products?

Cheers

Jim