I have a 1975 XJ6L, the running temperature can go up to 200 F while idling. Is this normal? If not, what can I do to keep the running temperature down to a reasonable level? I was thinking of putting an electric fan to make it run a little cooler, but I would like your all's input on this as well.

 

that sounds way too hot.

 

What's your idea of 'reasonable level'?

200ºF is nothing to be particularly alarmed about. Jaguar used both 180º and 190º thermostats in the 4.2 XJ6s. The aux cooling fan (as used on the Ser IIIs) was set to come on at 194ºF. You're not that much above that.

Does it keep climbing? Or is 200º about as high as it gets?

In any case if you wanna get it a bit cooler there's nothing exotic about the cooling system. All the usual fixes apply. A good thermostat, good fan clutch, and having the radiator professionally cleaned is usually all it takes to bring temps down a bit.



Cheers
DD

 

My idea of a reasonable level can be just about anything, but if I have it overheat too often, I'm going to end up with a burnt up engine. Is there a factory spec for when the 4.2L engine is at idle? I currently have a 160 F thermostat installed, it is just a standard thermostat from Pep Boys, it isn't a Waxstat. I have the Haynes manual, and it says that I should be running at about 160 F, is that close to factory spec or not?

 

200ºF in and of itself isn't hot enough to do any damage, providing you have good coolant flow throughout the engine. That is, no hot spots/clogs/steam pockets.

You mentioned it goes as high as 200º at idle. What does it run at while driving? If it drops significantly while driving along then the thermostat probably isn't stuck but your fan clutch might be faulty.

What are your ambient conditions?

A 160º thermo sounds low to me....I would've expected more like 180º on a USA-market car for emission reasons. Later Ser III cars with the 4.2 used a 190º 'stat. But, no matter...you're obviously running well above 160º anyway. Assuming the thermostat is opening fully then the cooling system simply isn't capable of holding temps down....eihter because it is faulty in some way or it simply lacks, by design, the ability to do so.

Cheers
DD

 

@ doug. I think it was 2 summers ago that my 86 xj6 was running hot (high green on the gauge). soon after my water pump went. I thought you hadc told me that normal was around 80-90. Am I getting my temps (c and F) confused?

 

In a word ...yes!
Fahrenheit went out with the dark ages, (ducks, runs for cover), mind you I still weigh myself in stones. Unfortunately I'm a few kg over.

 

Possibly

90ºC = 194ºF

Cheers
DD

 

Well 200F is about 93.3C so no, it's not running too hot in my opinion, if this is as high as it gets.

 

Only in metric countries. I think in F's, but recognize Z's as well. As the metric system has never been completely adopted in the USA, we find both. OK by me. But, who cares what is OK by me? My only complaint is having two sets of sockets and wrenches. Up til I got my first VW in about 1960, one set was enough. Although, I did change the transaxle in my 56 sans metric wrenches or sockets!!! .

The speedo's in my cars read in K's and M's. I ignore the K's.

Just before we came home from Germany in 1955, I bought a very nice 1950 Chevrolet four door. It was assembled in Belgium. Almost exactly like it's USA bretheren, except for it's K reading speedo. No matter, I merely converted in my head enough to avoid the cops!

200 F is just short of boiling at sea level, 212F. A reason for pressurized systems is to allow that without loss of coolant. My lump operates quite happily between 190F and 200F. Designed to do that with reverse flow to avoid harmful steam pockets.

Factoid: Themostats do not create or destroy temperature. They merely govern whatever is there. If they stick open, the engine may take a long time to warm up and possibly never get to an optimum number. Stick closed and an over heat quickly results. They are also a comfort item. To allow a quick warm up and keep miladie's toes warm on a cold morning by allowing early heater function

Now, the issue of omitting s thermostat to cure an overheating engine has been hashed out over the decades. They do not. Some even say they promote it!!

Caveat: The Jaguar has a green band on the guage that is leads one to believe that is OK. Tisn't. Don't ask!!

Well, Coco has his breakfast and I'm sipping a nice cup of black Nestlé's Classico. Yum, good.

Carl

 

200 is ok but there are a few things you can do to help on the front side. too. You could remove the radiator an flush it. Sediment often collects the at bottom and the only proper way to flush a radiator is to remove it from the car. When you remove it you will likely find debris that hinders air flow is easier to clean up. Also make sure you clutch fan is moving enough air and the shroud is in place and not cracked.

 

im a bozo-got my c's and f's confused. should have paid more attention in science class