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Old 22-02-2011, 06:10   #1
crusaderxvx
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rover 75 diesel cooling system.

Hi Good morming. can anybody tell me how the cooling system works. ie water from the bottom hose goes to the pump, normally water from the thermostat goes to the top of the rad, but it doesnt seem to do this on the 75 cheers Ian
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Old 22-02-2011, 12:22   #2
T-Cut
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The cooling principle in the diesel is the same as any other engine. The physical layout may look different, but coolant flow is basically the same.

The flow from the head/thermostat goes to the radiator top through the large upper (tapered) hose. Several members have inserted an inline stat within this hose to improve (increase) the running temperature.

TC
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Old 22-02-2011, 15:25   #3
FrenchMike
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Hi,

a little diagram to see how it works:



Mike

Last edited by FrenchMike; 22-02-2011 at 15:35.
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Old 22-02-2011, 16:45   #4
crusaderxvx
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Hi Mike thanks for the diagram. do you know where inline stat should be placed? and why the rad and bottom hose stays cold? cheers Ian
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Old 22-02-2011, 16:55   #5
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Quote:
Originally Posted by crusaderxvx View Post
Do you know where inline stat should be placed?
Looking at French Mike's image, it goes in the large central hose running from top of engine to top left corner of radiator (as viewed from front).The hose is cut to insert an aluminium housing. I believe an alternative is to use an in-hose type, which presses into the hose (no cutting).

Quote:
why the rad and bottom hose stays cold?
Coolant exiting the bottom of the radiator has normally flowed down through it and is therefore colder than the upper input. With the diesel, the input is often quite cool anyway due to stat failure. Typically 60-70C, which in engine running terms is cool. After passing through the radiator this fluid will be distinctly cold.

TC
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Old 22-02-2011, 17:18   #6
crusaderxvx
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Originally Posted by T-Cut View Post
Looking at French Mike's image, it goes in the large central hose running from top of engine to top left corner of radiator (as viewed from front).The hose is cut to insert an aluminium housing. I believe an alternative is to use an in-hose type, which presses into the hose (no cutting).

Coolant exiting the bottom of the radiator has normally flowed down through it and is therefore colder than the upper input. With the diesel, the input is often quite cool anyway due to stat failure. Typically 60-70C, which in engine running terms is cool. After passing through the radiator this fluid will be distinctly cold.

TC
Hi TC thanks for the input cheers Ian
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Old 24-02-2011, 04:49   #7
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hI. AND THANKS FOR INPUT. on the diesel the thermostat is the other side of the engine, water flows across the head, and exits from the side on its way to top of rad.

does any one know where the coolant is fed to from the filling resevoir, i suspect the engine block?

trying to get as much info as possible on the cooling system. and experimenting with inline thermostats.

objective is to inprove engine and heater operating temp.

also ideal to be able to replace stat if necesary. maybe an in hose stat? as used on some cars.

when i get a workable system, will share for others the results.
cheers Ian
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Old 24-02-2011, 09:37   #8
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Quote:
Originally Posted by crusaderxvx View Post
Does any one know where the coolant is fed to from the filling resevoir, I suspect the engine block?
It's all explained in French Mike's image. The header tank isn't part of the circulation loop. It simply ensures that the loops remain flooded by being positioned higher than the engine. Coolant added to the header passes into the system via a T-piece in the heater pipework. Once coolant gets into the coolant flow, it never gets back into the header, other than through temperature expansion or a severe overheat.

TC
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Old 24-02-2011, 09:46   #9
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Quote:
Originally Posted by crusaderxvx View Post
objective is to inprove engine and heater operating temp.

also ideal to be able to replace stat if necesary. maybe an in hose stat? as used on some cars.

when i get a workable system, will share for others the results
There already is a workable system that fits into the top hose - ranging from a few pounds (a Renault in-hose thermostat) to a spun aluminium housing holding a Chevy thermostat available from an American drag racing suppliers.

All seem to work well. What problem do you think needs solving?
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Old 24-02-2011, 20:39   #10
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Hi.

Just like to say i have just fitted an inline stat from: http://www.specialist-components.co.uk/

and it works a treat.

They have a few listed on ebay, they an't cheap at nearly &70 (roughly) but it takes 15 mins to fit and top the coolant back up, as oppssed to the estimated 3-4 hours to replace teh original unit.

and it looks nice aswell, is a nice turned aluminium unit.
Not sure what stat it has inside but im sure its just a universal 88degree unit.
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Old 24-02-2011, 21:04   #11
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Originally Posted by djyare03 View Post
and it looks nice aswell, is a nice turned aluminium unit.
Not sure what stat it has inside but im sure its just a universal 88degree unit.
It's a 90c stat from a Chevrolet.

I had one, but never got chance to fit it. My engine died (not related to the stat or temp) and I had a replacement fitted, so I had them fit a brand new OEM stat while the engine was out. Sold my Specialist Components stat to another 75/ZT owner.
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Old 25-02-2011, 07:16   #12
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It's a 90c stat from a Chevrolet.
Are the Specialist Components supplying Chevy stats now? I thought they came with some shoddy 'Mini' 88C ones with some random (and pointless) hole drilled in them?
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Old 25-02-2011, 10:06   #13
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Quote:
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Are the Specialist Components supplying Chevy stats now? I thought they came with some shoddy 'Mini' 88C ones with some random (and pointless) hole drilled in them?
I fitted a Specialist Components inline stat a couple of weeks ago, it came with an 88C stat without any holes drilled in it. So far all works well with engine temp cycling between 86C and 96C as the stat opens and closes. Not sure if its a Mini stat or not. The car (without a FBH) still takes a good 7 miles plus to reach 88C which is a great improvement on never going above 67C during the previous couple of months.
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Old 25-02-2011, 11:09   #14
Mintee
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I fitted a Specialist Components inline stat a couple of weeks ago, it came with an 88C stat without any holes drilled in it.
Why did some have holes drilled in them? That has never been answered has it?
Quote:
Originally Posted by Mike123 View Post
Not sure if its a Mini stat or not.
I got idea it has a Mini thermostat in from here.
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Old 25-02-2011, 11:20   #15
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Are the Specialist Components supplying Chevy stats now? I thought they came with some shoddy 'Mini' 88C ones with some random (and pointless) hole drilled in them?
No, you're right... sorry wasn't thinking straight. Mine did have a hole drilled in it, but I had swapped it over for a 91c QTH-107 stat.
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Old 25-02-2011, 11:30   #16
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[QUOTE=Mintee;4298644]Why did some have holes drilled in them? That has never been answered has it?

I think there was a concern that coolant would not wash over the wax filled sensor that operates the thermostat but it was later found that coolant leaked past (by design?) anyway so the drilled hole was slowing/preventing warm up as too much coolant was entering the radiator before the thermostat opens.
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Old 25-02-2011, 11:35   #17
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No, you're right... sorry wasn't thinking straight. Mine did have a hole drilled in it, but I had swapped it over for a 91c QTH-107 stat.
What temperatures are you getting using 91c QTH-107 stat ?
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Old 25-02-2011, 15:22   #18
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I've yet to fit it, but I'm going to to use a 92C Opel unit, as it's the highest temp I could find
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Old 25-02-2011, 18:53   #19
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What temperatures are you getting using 91c QTH-107 stat ?
Like I said above, I never fitted it - as my engine was taken out of the car, I had the OEM thermostat replaced instead, and sold the Specialist Components housing.
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Old 25-02-2011, 21:21   #20
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I've yet to fit it, but I'm going to to use a 92C Opel unit, as it's the highest temp I could find
What is the advantage of a 92C thermostat ? What running temp are you hoping for ?
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