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The temperature conundrum solved......


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Some of you may recall I have changed something like 15 stats in my 4.6, tried making restriction plates and all sorts to get a stable temperature in the engine.

I have had stats opening late, closing early, temps at the top of the engine appriaching 120 degrees C and a very worried look on my face more than once.

With restriction plates instead of stat, the engine runs cool 65 degrees, so I know I have the cooling capacity, just not the control.

So, last night I gets to thinking.... I had temp issues with the 3.9 and ended up with an 82 degree stat.

When the 4.6 went in, it was a new water pump and all new hoses... Now it has new rad too.....

So I started looking for the constant. THE HEATER MATRIX !!

So if Rover designers were't all that bad, and most everyone elses truck works... Maybe something they thought of is not happening in my engine. Maybe not enough water is flowing around the heater matrix and the lack of flow is causing hot spots in the inlet manifold.

So to check the theory tonight, I removed the heater matrix from the loop, plumbed straight from heater outlet on inlet manifold to return point in radiator.

Took it for a drive.. Rock steady between 84 and 92 degrees, moved only slightly dependent on level of right foot....

Totally different temperature profile and the cooling system doing it's job.

I can only assume when I've previously flushed the heater matrix through, the water under hose pressure look like a good flow, but was totally inadequate when compared to the original design requirement...

So, problem solved, new heater matrix required....

Neil

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I'm sorry I didn't pick up on this earlier.

On V8's the heater circuit provides circulation through the engine & pump even when the stat is closed.

You must have flow through this circuit, even if it's just looped back and not connected to a heater matrix, otherwise the stat never sees the real temperature of the engine and you'll get horrific hot spots.

Some of you may recall I have changed something like 15 stats in my 4.6, tried making restriction plates and all sorts to get a stable temperature in the engine.

I have had stats opening late, closing early, temps at the top of the engine appriaching 120 degrees C and a very worried look on my face more than once.

With restriction plates instead of stat, the engine runs cool 65 degrees, so I know I have the cooling capacity, just not the control.

So, last night I gets to thinking.... I had temp issues with the 3.9 and ended up with an 82 degree stat.

When the 4.6 went in, it was a new water pump and all new hoses... Now it has new rad too.....

So I started looking for the constant. THE HEATER MATRIX !!

So if Rover designers were't all that bad, and most everyone elses truck works... Maybe something they thought of is not happening in my engine. Maybe not enough water is flowing around the heater matrix and the lack of flow is causing hot spots in the inlet manifold.

So to check the theory tonight, I removed the heater matrix from the loop, plumbed straight from heater outlet on inlet manifold to return point in radiator.

Took it for a drive.. Rock steady between 84 and 92 degrees, moved only slightly dependent on level of right foot....

Totally different temperature profile and the cooling system doing it's job.

I can only assume when I've previously flushed the heater matrix through, the water under hose pressure look like a good flow, but was totally inadequate when compared to the original design requirement...

So, problem solved, new heater matrix required....

Neil

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Errr.... Only a couple of years !! :o

You sorted your wobble yet Pete? (Shall I start the timer...)

Neil

Yep, wobble fixed. Fitting new wheels and tyres seems to have solved it. I suspect that one of the tyres might have been outta shape. I'll ping you a pm later.

Pete.

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I'm sorry I didn't pick up on this earlier.

On V8's the heater circuit provides circulation through the engine & pump even when the stat is closed.

You must have flow through this circuit, even if it's just looped back and not connected to a heater matrix, otherwise the stat never sees the real temperature of the engine and you'll get horrific hot spots.

Hi Matt,

I had the heater matrix in it's own circuit as designed, so assumed it was working fine because I could see a flow rate. What I've established is I didn't have enough flow rate and that all that water making it's way to the top of the engine was milling around getting hot instead of all being circulated and gradually heating up behind the stat.

I can now see that it's effectively two complete circuits, one for warm-up, and then the bigger circuit for mainstream cooling.

I'm glad I thought it through finally.....

I hope the thread helps others who may experience similar issues...

Neil

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Hi Matt,

I had the heater matrix in it's own circuit as designed, so assumed it was working fine because I could see a flow rate. What I've established is I didn't have enough flow rate and that all that water making it's way to the top of the engine was milling around getting hot instead of all being circulated and gradually heating up behind the stat.

I can now see that it's effectively two complete circuits, one for warm-up, and then the bigger circuit for mainstream cooling.

I'm glad I thought it through finally.....

I hope the thread helps others who may experience similar issues...

Neil

It has me thinking about a problem on the nas that has been niggling me for some time............................

Even with a new engine from Turners and new radiator from Land Rover last year the 3.9 moves the temp gauge from 1/3 to 1/2 FSD when working hard. Could try the taking a loop of hose around the engine trick now its warmer. :lol:

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It has me thinking about a problem on the nas that has been niggling me for some time............................

Even with a new engine from Turners and new radiator from Land Rover last year the 3.9 moves the temp gauge from 1/3 to 1/2 FSD when working hard. Could try the taking a loop of hose around the engine trick now its warmer. :lol:

Certainly worth a try.

I'll be pulling the heater apart soon, so will tell you what sort of a challenge you may be in for ! :)

Neil

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