4200 Thermostat Replacement

richard_masa_4200

Junior Member
Messages
195
A couple of weeks ago I had the misfortune to see my temp gauge creep past 90. Stay calm I thought, it's probably just the 30+ degree day in sunny Melbourne. As long as I keep moving we should be ok. Oh ****, traffic. Upwards the needle marched. I pulled over and waited for the traffic to disappear and then rushed back home.

So it would seem my thermostat had given up. Would this be an expensive trip to the indie, or could I do it myself? After a bit of research I figured I could do it myself.

I ordered a new thermostat from eBay in the US and it arrived about 10 days later. I also decided to go without coolant (it doesn't get near freezing in Melbourne) and are trying Redline Water Wetter with distilled water. I put the front end on stands and proceeded to get to work.

The thermostat is on RHS bottom of block at the front. It is easier to tackle from underneath. A few pointers.
1. Remove the bottom radiator hose from both ends as it gives better access to the thermostat.
2. Remove the top hose from the radiator, but leave it connected to the thermostat, it's easier to remove it as one piece.
3. When fitting the new thermostat attach the top radiator hose to the thermostat housing and fit as 1 unit.
4. Flush the radiator well before putting it all back together.
5. It would help if you had the hands of a Japanese schoolgirl. However, I have the hands of a rugby player and I still managed ok.

I filled her with the new water mix and let her get up to temperature. Yay, sitting just under 90. As it should.

I took her for a spin down the Great Ocean Road on the weekend and she is back to her normal cool self. Definitely a job you can tackle yourself if you are kindly mechanical.

Rich.
 
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conaero

Forum Owner
Messages
34,631
Nice one Rich. I noticed the other day that mine was constantly hitting just over the 90 degrees and its cold over here, 5-7 degrees so I think mine is on its way.

Any chance you can point me to the EBay link????
 

CatmanV2

Member
Messages
48,794
I ordered a new thermostat from eBay in the US and it arrived about 10 days later. I also decided to go without coolant (it doesn't get near freezing in Melbourne) and are trying Redline Water Wetter with distilled water.

Rich.

Good stuff, Rich. Does Water wetter provide the same corrosion inhibition that I was led to understand is a vital factor with modern coolant / antifreeze, or is it no required with the 4.2?

C
 

CatmanV2

Member
Messages
48,794
Nice one Rich. I noticed the other day that mine was constantly hitting just over the 90 degrees and its cold over here, 5-7 degrees so I think mine is on its way.

Any chance you can point me to the EBay link????

What's the normal temp for these? Mine heats up surprisingly quickly (at least compared to the old Alfa V6), but when it gets above 90, the fans come on and it comes back down. Seems to run between 80 and 95.

C
 

richard_masa_4200

Junior Member
Messages
195

richard_masa_4200

Junior Member
Messages
195
Good stuff, Rich. Does Water wetter provide the same corrosion inhibition that I was led to understand is a vital factor with modern coolant / antifreeze, or is it no required with the 4.2?

C

I'm working from a recommendation from a mate that prepares race cars. He advised me that water wetter does have an anti corrosion property when used with distilled water. He only runs this mix in the race cars. I'm happy to stick with it at the moment and see how she goes. Now that I have done it once before I would be fine with doing a quick coolant change if I needed to.
 

abyss

Junior Member
Messages
108
Great work Richard. I've done the stat changed in my Alfa GTA before and it was quite easy.

When you say 50c on highway was it the normal temp or abnormal temp? Mine seems to be around 90c at most time doesn't matter is traffic or highway.
 

Geofflyn

New Member
Messages
560
Great work Richard. I've done the stat changed in my Alfa GTA before and it was quite easy.

When you say 50c on highway was it the normal temp or abnormal temp? Mine seems to be around 90c at most time doesn't matter is traffic or highway.

Yes mine too is constantly in the 85/90 range regardless of where I am . The only time its gone slightly higher was our drive a couple of weeks back through the Otways. A 35 degree day with lots of hills but even so I dont think it got above 95.
 

richard_masa_4200

Junior Member
Messages
195
My temp on the freeway is definitely around the 50 range as I expect it to be. With an ambient temp of around 22 and a constant 100 km/h between Melbourne and Torquay I would expect the airflow to keep the engine relatively cool. Maybe the GS behave in a different way?
 

conaero

Forum Owner
Messages
34,631
My Spyder seems to hit the fans too easily and its cold over here.

My concern is that when it gets hot over here it might become an issue.
 

BennyD

Sea Urchin Pate
Messages
15,006
Might I suggest that 50c in the cruise with a high ish ambient temperature is, IMO, a bit on the low side. I reckon that 75c would be about normal and the thermostat usually starts to open at about 88c. If the fans keep it at 90cn traffic then all is ok but if the temp climbs something is wrong. The problem you might get at 50c is the ECU getting told that the engine block water is still a bit cold and schedules more fuel, which may wash the bores over time as well as use more fuel than it should. IMO, a good working range is 75-90c
 

conaero

Forum Owner
Messages
34,631
Also Benny my idle revs are at 1000 rpm which I think causes the overheating when stationary.

What's your idle rpm Benny....or any of you other 4200 owners?
 

CatmanV2

Member
Messages
48,794
I noticed mine was a tad higher after a warm start yesterday, but I think it dropped again. Will check another time. Certainly in no fit state to drive now :)

C