[Bruce 94VT]

Hi
Just before I purchase a thermostat for my 94VT, I would like to confirm that the NAPA number THM 399198 or THM 148 is the correct number. Can anyone confirm this please?
Kind regards

 

[Sledge4.2]

Is it overheating or is there an issue Bruce?

 

[Bruce 94VT]

No it isn't Sledge. It is running fine thanks mate. I have been buying spare parts for the car for a number of years, just to have spares ready just in case something fails. I have never thought about buying a thermostat for the spares cabinet. It might be a bit overkill with what I am doing but I don't like the waiting game for parts if something fails.

 

[Bruce 94VT]

I was just hoping someone would confirm the correct part number.

 

[mikael82]

Hi
Just before I purchase a thermostat for my 94VT, I would like to confirm that the NAPA number THM 399198 or THM 148 is the correct number. Can anyone confirm this please?
Kind regards

I can not see Napaonline in Europe so I can't see what those numbers are and for what cars they go.

But this is original Diablo thermostat:
Behr B.476.74

 

[Bruce 94VT]

Thanks Mikael. Where would be the best place to purchase one of these please?

 

[mikael82]

This is not so simple thing...

What temperature should thermostat have? Factory says 74 celsius.
Fans will kick on att 80 celsius and off again 74 celsius.

There for temperature for thermostat should be 74 celsius, am I right?
(I am asking this because Paul has refered temperature rage being 79 celsius and that is too high in my opinion.)

 

[Bruce 94VT]

Thanks Mikael. It would be great to know. I have looked for the BEHR B.476.74 without any luck. Does anyone know where these are available please?

 

[mikael82]

Original temperature for opening of Diablo thermostat is 74 celsius.

I also have 79 celsius thermostat that is aftermarket. (infact my car did not have thermostat att all! and you can't run it without one.)
I have couple of options coming in to replace:

-Original 74 celsius that is sceary expensive.
-80 celsius unit that is too high temperature.

Issue is that there is no right sized alternative to replace original, but I try to see if I can modifi one to fit.

(Issue with thermostats for me is that here up north they only sell "winter" thermostat that are always little higher temperature, so I have to order all "summer" thermostats from central Europe.)

 

[Bruce 94VT]

Looking forward to your findings mate. I too am speaking to someone who believes they have a solution. Will update as soon as I find out more.

 

[Bruce 94VT]

This is what came out of my workshop manual Mikael

 

[Bruce 94VT]

I found some cross reference parts on b.476.74-b.476.74 Coolant Thermostat . I hope these help.

 

[paul01]

Hi,
yes i use a thermostat that opens at 79°C and i am happy with this one.

But the 74°C that Mikael mentioned above is ok. Here ist my old research:

Workshop manual also will show a 74°C one:

The oil thermostat opens at 80°C. So the 79°C water thermostat is the best for me.

Does anybody drives his car with oil or water under 80°C ? I dont think so.

E.g. if you have a watertemp of 85° the thermostat is fully open. Then it doesnt matter wich one you use.

It is not possible to run cooler with a thermostat that opens earlier. It makes only a difference while warming up. And downhill.

Paul

 

[Bruce 94VT]

Where I live, it is hot and very hot 9 months of the year. Would this thermostat you are talking about paul01 be any good for my weather conditions?

 

[Bruce 94VT]

Would that be the NAPA TH148 paul01?

 

[paul01]

Bruce, i have to look to that later today.

But if you have the 74°C type then no need to change. It will not be better with 79°, but also not worse.

The game is this:

If you have a temp problem or you want be in the range 80°C...90°C the thermostat has to open at the lowest temp or a few degrees below (not much). Or simply use the lamborghini values.

Next thing is to be sure that the thermostat opens completely and closes also.
Also no air in the system (old diablos have automatic system) and water pump working.

All the other things: the outer water circle. Most important is the area with the both radiators. Best is if this area is all the time cooler than the thermostat open temp.

Both fans running ?
Also ok is if the fans stop working many degrees below the thermostat open temp. They should do all for keeping the temp difference outer circle/inner circle.

Paul

 

[paul01]

Hi,

don´t know NAPA parts.

I use this one : Behr TX 97 79D

see also: https://www.lamborghini-talk.com/vbforum/f45/odd-coolant-temperature-behavior-184210/

Paul

 

[mikael82]

If your thrermostat is working and no issues; do not change it.
There are only old stock thermostats left and when those are gone, there are no more.

Thermostat should work with radiator fan switch, so it gives radiators full change to cool down engine and that is with thermostat being fully open if this does not work radiator fans will cool it down.
This is how system works:

Radiator fans work:
80 celsius "on"
74 celsius "off"

Thermostat works:
74 celsius start to open
86 celsius fully open 7mm



Radiator fans keep car att operating temperature.

If you have thermostat higher:
Thermostat opens 79c (and fully open?)
Radiator fans start 80c

In this case: when thermostat opens radiator fans will be "on" same time.
Radiator fans will cool coolant to 78c and thermostat is closed and inner "warm up" sicle is open.
Issue here is that thermostat is never fully open, because radiator fans will cool it closed imidiatly so cooling system does not fully open (or close inner "warm up" side)

This is why you should use 74 c thermostat;
cooling system is fully open (and inner "warm up" side closed) when radiator fans work, coolant flow is maximum because it is not just thermostat operating temperature it also to do with coolant flow.

 

[Bruce 94VT]

Can you advise where to purchase the thermostats you are talking about Mikael?

 

[Bruce 94VT]

I am not having a problem with mine but it the correct thermostats are few, then I would like to purchase one before there are no more.