AJP coolant temperature - opinions please

[MoonMonkey]

Ever since I have had the Cerbera I have had problems with the thermostat (it overheated 10 miles after buying due to a seized thermostat)

I replaced the seized thermostat with a Gates pattern part equivalent to the Quinton Hazell QTH134, which has an opening temperature of 79oC. This has worked fine but as the weather has got colder the coolant struggles to get higher than 80oC, particularly on the motorway.

I noticed that the original thermostat made by Wahler operated at 85oC, and I have tried to replace the thermostat with a QTH221 (made by Wahler) that operates at 85oC twice, but on both occasions the thermostats have not worked (confirmed in a bucket with hot water - I will now check in the bucket first)

So my question, while running cooler may be a good thing, I'm just a bit concerned that I'm running a bit too cold, and I may be losing out on lubrication due to cooler oil. I guess the sensible thing would be to install an oil temp gauge. What are people thoughts about the optimum oil / coolant temp?

I really can't face changing another thermostat!

[Supateg]

I struggle to get over 80 degrees on the motorway in cold weather (freezing or just above)
In town normal temps.
Do you have an oil stat fitted?

[gerradiuk]

Fitted Quinton Hazell QTH134 in August 2012 no problems,also see 70 on motorway but heater basts the heat out fine.

[MoonMonkey]

That's encouraging, I was getting worried the other night on the M56

I don't have an oil stat fitted but sounds like it might be a good idea.

I've noticed on another thread oil temps of 50-60oC were not uncommon, so maybe it's not as bad as I thought.

I have been running Mobil 1 0/40's so maybe better for the lower temps.

Thanks

[sonnylad]

Are you fitting it this way up:

[MoonMonkey]

Hi Sonnylad

No I've been fitting the QTH 221 this way up


i.e. Radiator top hose connected to the top, by pass back to the water pump to the bottom, and feed from engine manifolds to the left


When I looked at it, that seemed to be the way the bypass allowed coolant back to the pump and blocked the top radiator feed until the stat opened. When I tried in a bucket of hot water the stat failed to open as well

Which is correct?

[sonnylad]

The correct way is as shown in the picture i posted.

[MoonMonkey]

That might explain things!

Although I'm not sure why they are not working when I put the thermostat in a bucket of hot water?

[sonnylad]

I would deffo check again with hot water from kettle, but fitting your way will cause problems with water flow.

[N7GTX]

When replacing all the pipes with the ACT stainless and pretty blue stuff, I bought a 'new' stat from a dealer. Fitted it correctly and it overheated. Removed it and refitted the original and in temps like we have now, reads around 80c when on A roads and goes up to 90c when in town.

[MoonMonkey]

I'll give it another go in the bucket, not that I'm looking forward to changing again! I must have spent the best part of £100 on antifreeze already.

That will teach me not to take photo's/make drawings before you take anything apart.

At least I have the nice shiny pipes and blue hoses now, so should make it easier to change

Thanks

[Warwick67]

Mine runs cold in cold weather, on the motorway it struggles to get much above 70 on a really cold day....

[Vee8ight]

I get around 75-80 in cold weather too, not sure which way up my stat is or which one I have fitted! Was wondering about a retrofit oil stat if there's such a thing?

[spitfire4v8]

I don't know what angle sonnylad looks at his thermostat .. upside down through a miror I think.
Every cerbera thermostat I've ever seen have been fitted like these:

[MoonMonkey]

spitfire4v8 said:

I don't know what angle sonnylad looks at his thermostat .. upside down through a miror I think.
Every cerbera thermostat I've ever seen have been fitted like these:

That is how I've been fitting the QTH221's, I must be unlucky buying 2 that would not work? It's a pity as the workings of the 221 look so much more robust than the Gates one. Just hope it flows enough to keep cool on a track day.

From every bodies experience it seems 70-80oC on the motorway is pretty normal so I guess I'll leave it in - if it works don't fix it!

Many Thanks for the help

[sonnylad]

I could have sworn they were fitted like that, my apology.

It has been a while since i had one fitted.

[FarmyardPants]

It should never run more than a few degrees colder than the stat temp if the stat is working properly. At 70c the stat should be closed and the water should heat up, regardless of speed and ambient temp. In freezing weather on the motorway mine runs at about 82 on the gauge.

[assynt road]

I recently had a new stat fitted because the old one didn't close when coolant temperature fell, unfortunately the new one failed to open at all... leaving me boiling away merrily. The 2nd replacement stat works perfectly now, so getting a duff one isn't unusual.
Did hear somebody say that some differing makes of stat looked identical whilst actually being plumbed differently ?

[MoonMonkey]

The thermostats I've had didn't look exactly the same but they are plumbed differently. From my experience in the last couple of months I've seen 2 basic types:

The Quinton Hazell (Wahler)


and the Gates type


When you look at them, it is easy to get confused as to how they should fit as they do operate slightly differently, but I think I've got it right now.

The Quinton Hazell ones certainly look more robust and seem to have a bigger bore, which should give better flow, but all the QH stats I've had in the last couple of months have failed.

[Vee8ight]

I've read on a parts site that some stats don't flow enough, is this true?