oil and coolent temps with Mobil 1?

[Doug Hillary]

Hi,
Shannow - you got it. So did the Germans many years ago - -30C nights in Zuffenhausen, Wolfsburg and Munchen probably helped a bit too

Well, after they all got over the hot exhaust valve on one pot on aircooled VWs

A bit like lovely Lithgow in mid winter - joking!

Queenstown and the Southern Alps in NZ's midwinter gave me the message in the 1960s!

Some Benz truck engines including V10s had a twin thermostat set up to reduce thermal shock and the cold lower bore/liner problem

33C and **** humid here today so the Porsche's cooling system had all ports open a little - at 180km/h Shhhhhhh don't tell Mr Plod!

Regards

 

[Dr. T]

I concur...thermostat stuck open. I just replaced mine for the same reason. There is no car that needs 1/2 to warm up...unless the temps. are below -20 to -30C...how would you ever get heat?

Secondly, you guys got me messed up....the thermostat is on the TOP hose because that's the one that determines whether hot engine coolant is permitted to enter the rad to cool off and then re-enter the engine. The lower rad hose should be cold/cool all the time....else you also need a new rad....demonstrated by the temp. needle rising on the dash.

 

[Doug Hillary]

Hi,
DrT - I respectfully request you re-read the previous posts
We are not talking about "heater" warm we are talking about the engine's core temperature - all systems

Regards

 

[Wagonmaster261]

For what it's worth...
I have a '94 Corolla, 4A-FE, Auto., Formula shell 10W-30, no additives, 170k.
The outdoor temps have been around 20-35 deg. for a while around here.
The coolant gauge on the dash usually stays close to the bottom mark while moving.
When idling, the gauge will get about halfway up the scale, start moving and it drops.

 

[Shannow]

Dr. T,
the process was counterintuitive for a while, until I decided that a thermostat in the top hose actually controls the temperature of the water entering the radiator, not the temperature of the engine.

Say the water exiting the block is high. The thermostat opens, and allows water to flow at a greater rate until the cool front hits it. The first cylinder(s) will have a period of time with really cold water. The thermostat will sense the cold water only after the water reaches it, and react by closing in, allowing it to circulate until it warms back up again

A vast oversimplification, as the system is always open, and it's warm versus a bit more warm, etc.

The bottom hose thermostat has a bypass from the top hose, and "mixes" a coolant supply at 160F. If the engine is running 160F, none is sent to the radiator. If it's 180F, the engine recieves water at 160F. If it's 200F, the engine (and therefore the front cylinders) recieve water at 160F. (Give or take a little bit).

I must admit that the thermostats lasted a year at best, which I take to meant that they are working harder in a less well damped (from the thermostat's viewpoint) system.

 

[Drew99GT]

quote:

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Originally posted by Wagonmaster261:
For what it's worth...
I have a '94 Corolla, 4A-FE, Auto., Formula shell 10W-30, no additives, 170k.
The outdoor temps have been around 20-35 deg. for a while around here.
The coolant gauge on the dash usually stays close to the bottom mark while moving.
When idling, the gauge will get about halfway up the scale, start moving and it drops.

---

If your gauge drops like that while moving, you for sure have a stuck open thermostat, which is common on older Toyotas. Mine did the exact same thing. After I replaced the thermostat, the gauge reaches half way between cold and hot (which is the normal position for it) and never ever moves, even when it's very cold out. And it doesn't take very long to get hot as well, but like I posted above, the lower radiator hose remains ice cold because the thermostat never opens.