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How I Fitted my Low Temp (160F/71C) Thermostat

GT4

Well-known member
Joined
8 Nov 2008
Messages
30,181
MOD: moved to FAQ

Did this today round a friend's house (a selection of his Snap-On attachments were useful, as was his slightly sloped drive)

Recipe:
WD-40 (always!)
Hartech Low Temp 160oF/71oC thermostat insert
Some spare coolant (I bought 1 litre - although so far I have 0.5L left)
Some distilled water (I bought 1 litre - although so far I have 0.5L left)
Thermostat housing gasket (996.106.326.50)
10x14x1mm crush washer (sealing ring)
Gasket sealer gunk (I used Loctite 5922)
Emory/wet and dry paper and/or scouring pad and/or razor blade
Ideally some disposable gloves so your hands are nice and clean.

Tools:
Clean bucket (or two for good measure)
Funnel
Jug
Old T-shirt or similar clean cloth for coolant filtering
6mm Allen drive (or key)
Medium Flathead Screw driver (or 6mm 1/4drive socket) - for Jubilee clip
10mm Socket
Assorted rachet/extension/universal joint
Trolley jack(s) + wood block to spread weight on sump
Axle stands
Wheel chocks

Method:
1.) Open the engine lid

2.) Chock, jack and axle stand your car (I raised mine by about 20 degrees to staunch coolant flow and hence airlocks and allow access) - If you decide to incline your car too you must chock because the front axle has no handbrake nor gearbox braking (excepting slight C4 wind-up if left in gear)

3.) Spray the penetrating oil (WD-40) on the 3x hardline bolts, 4x thermostat housing bolts and the jubilee clip - leave to penetrate!

4.) Drain coolant using drain plug (6mm Allen drive) and header tank cap for flow control - mine dumped approx 8 litres (or approx 2/3-3/4 bucket) - the plug is to the rear of the sump - most comes out in less than a minute (only remove the header tank cap once the flow seems to be lessening). I left another bucket to collect another 0.5 - 1L over the next 10 mins whilst I had a cup of tea.

5.) To ease access, free the coolant hard line that circles the sump (3x 10mm head bolts).

6.) Loosen the jubilee clip with flathead screwdriver (or 6mm socket) and pull off the rubber pipe to the thermostat housing - be prepared to catch another cup of coolant (or not!)

7.) Now unscrew the 4x 10mm head bolts that holds the housing on.

8.) Gently knock the housing off and peel the old gasket off.

9.) Clean both sealing surfaces - the housing is safe to use any of the emory/wet and dry paper and/or scouring pad and/razor blade methods - just wash afterwards. I would suggest only using the scouring pad on the engine block to minimise debris.

10.) Remove and refit new thermostat insert (I just used an old cap from a spray bottle to compress the spring and rotate to release or fit)

11.) Carefully smear the housing sealing surface with gasket sealer gunk.

12.) Locate the gasket on the housing and apply gasket sealer gunk to the top side of the gasket too.

13.) Refit everything as reversal of removal, fitting new washer to coolant drain plug - LEAVING THE CAR JACKED.

14.) Now the refill: I placed the funnel with (pre-wetted) cloth filter in the coolant header/reservoir tank and just jugged the coolant back into the car.

Try to count the coolant out and back in - I was left with 3L left over on first fill (this represents the air locks present)

15.) Bleeding ("burping") - lift the bleed valve and lock into vertical bleed position.

16.) I carefully ran the engine car still jacked - I idled for a bit then checking no warning lights were on and the temp gauge was working I turned the heater to full temp (and A/C for assisted cooling as the car was stationary and running a partial system fill) - I then held the engine at 4,000 rpm for a minute. I then stopped the engine, lowered the car and and topped up the header tank with about a litre.

17.) On start up the heater started blowing through hot (which is good!). I then went for a drive, watching all the gauges and making sure the heating showed no signs of cold spotting. I checked the header tank again after 5-10 mins of driving - I topped up another 1L.

18.) This is at you own discretion, but given I knew I had only 1L left to refill and the header tank had a decent buffer, I gave the car the beans for another 10 mins (up and down hills and high-G corners and fast acceleration) and after that seemed to burp the airlocks effectively, I topped up with the "Final" 1L .

19.) Drop the bleed valve back to flat.

20.) Let the car cool and check the coolant level immediately before the next few drives and only cease checking when no change in level is evident - top up as necessary.

LIST OF ATTACHED PHOTOS (20160202)

1) Hardline bolts (Note: this is a supplementary support so I don't get squashed - DO NOT JACK HERE):

2) Housing bolts (two hidden by angle) and jubilee clip:

3) Coolant drain plug (actually pictured just before I screwed back in)

4) Coolant (looks green in the bucket, but it is pink :? ):

5) Housing off:

6) Cleaned up housing and the old tstat insert removed:

7) Old tstat thermal rating (83deg vs 71deg - sorry forgot to photograph the new one from the "top" :duh:)

8) Old tstat insert

9) New tstat insert fitted:

10) Funnel and filter (note some of the crap collected):

Bleed valve (Turbo location for illustration):
8IRbEL4A.jpg

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Great write up GT4. :thumbs:

Keeping your daily post average up to 8.5 a day as well. Fantastic effort.
 
Thanks.

Wish I'd just posted a :floor: tacked on the end of a joke thread.

That only takes 5 seconds.
 
Great write up. Thanks for sharing.. :thumb:
 
Brilliant thread again, I don't know why you spend so much time doing these threads but I'm sure gald you do :thumb:
GT4, how much would you say this cost to do and how long did it take you ?
Regards
Mal
 
Low Temp Stat = £84 (inc UPS nextday delivery, courtesy of Hartech)
Gasket - £3.98 (courtesy of OPC Cambridge and PCGB discount)
Crush washer - £0.22 (courtesy of OPC Cambridge and PCGB discount)
Coolant concentrate - £7.58 (courtesy of OPC Cambridge and PCGB discount, yes I know I could have bought a universal or Elf equivalent, but they are good to me and I got a free coffee and biscuits and a drive-out)
Distilled water - £0.79 (courtesy of Halfords, at that price it's not worth using dodgy tap water)

The other stuff I had lying around and the cup of tea and my mate's rubber gloves were free!

As for time, I did this as my first time on my own (which I am always extra careful with jack and axle stands and chocks etc), I stopped and took photos (actually about 55, but I didn't bore you with every nut and bolt) and I stopped for tea and coolant drain, left the WD-40 to penetrate, spent 20 mins cleaning both the sealing surfaces and basically enjoyed being out in Sunday's sun (and peering round the underside of my car - I even polished up my engine number and the "VarioCam" script on the side of the engine block - wish I'd photographed that to be honest, the "VarioCam" script was most odd as it was quite ornate and non-functional and I couldn't work out why they would have cast it when no one, except techies, would see it :dont know: )

But I guess about 2 hours including getting all the tools out and putting them all away again.

If I did it again, you weren't that bothered about cleaning the sealing surfaces and someone else did tool tidy-up, I suppose you could do a quick version in 30 mins (it's only one plug, seven bolts and one jubilee clip) - not including the burp drive.
 
Good write-up, thanks.

Slightly surprised at the products on the grass!

I am now awaiting new temperature readings, to see if I am going to bother with this.

What condition were your hoses in? have they ever been replaced?
 
peters said:
Slightly surprised at the products on the grass!

Why?

Don't worry - they were only gently placed on the grass for 10 seconds.

It was just to "pose" them for the camera (hence the "One Cal").

The grass was clean (if it makes you happy, I gave them another wipe over before applying the sealer gunk) or attaching the housing hose (which received a wipe around the inside too).

If it makes any difference, that is the old tstat insert on the grass (the new one never touched anything else other than the housing until it I placed it back in the engine)

Without recourse to my invoice file I am not sure about the hoses (and if they were replaced during warranty or sale prep by the various OPCs or JZM over its lifetime, then I have no record).

They looked fine and were still nice and "squashy", nice uniform black finish, no nicks, cracks or visual fatigue/degradation.

I intend to check the levels again today (now it has fully cooled overnight) and do an actual drive temp comparison (although even yesterday when it wasn't even fully burped and I was ragging it a bit, the temp was 6-7 degrees cooler - quite odd being used to seeing "8X" on the temp gauge and now "7X" - felt like I should still be warming it up.

Just shows the importance of the oil pressure gauge though on us poor 996s - even with the lower WATER temp, OIL temp (and presure) still attains normal parameters - I will confirm with more something more scientific and less cursory.

I also intend to perform another static (idle heat build) test, so I can chart with the other Pin-Up/Pin-Down thermal characteristics.
 
Nice write up GT4.

Did mine at the weekend but forgot to take the before temps across the engine. :oops: I'll keep an eye on my dash gauge to see if there is any change.

I have only driven it 5 miles since so never saw it fully up to temp yet and my pin on the header is still up until I can get to the car to top it up again.
 
Just popped home to check on mine.

Added another 0.5L now it is cold.

Will take for a run this afternoon/evening and leave overnight and check again tomorrow.

Fortunately I took extensive readings via the onboard digital temp gauge and via Durametric data logging.

So I have some data to compare it to.
 
Original post edited to confirm the car is on AXLE STANDS.

DO NOT JACK on the engine.

The engine jack pictured was a supplementary support whilst I was under the car incase either the axle stands gave or the car moved off its chocks.

DO NOT TAKE ANY UNECESSARY RISKS WHEN UNDER YOUR CAR

A few more pounds for another jack, some proper axle stands, some decent chocks or a few more minutes checking everything is in place and hasn't moved as you gradually raise the car could save your car or YOUR LIFE.

EDITED TO ADD MORE PHOTOS (20160202)
 

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Great write up GT4 Thanks.

I had one of these thermostats fitted last week during a major service and water pump replacement so its good to see what the mechanics at TWG Motorsport had to do.

BTW, TWG did a great job for me and I'd highly recommend their services.

Keep the messages coming - as a newbie with little knowledge of my car your threads makes good reading :thumb:
 
Had mine done at TWG today. Admittedly I only drove home though town but water temp still reading at 80-c

What's other peoples experiences? Does it run at noticeably lower on water temp gauge?
 
You should see it the low side of the 80 mark in normal driving:

EDITED TO ADD ACTUAL GAUGES TOO!

(and LOCTITE 5922)
 

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GT4 said:
You should see it the low side of the 80 mark in normal driving:

Ta, was reading slightly right of 80 mark before.

Will see how it reads on a bit more of a cruise.
 

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