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Basil
06-23-2001, 09:58 PM
Member Dakuhl, posted this question in another forum and I just thought it best to answer here in the Jag forum:

"well i've got a 1977 jag xj coupe, she's a beauty, a black beauty in fact with chrome wire wheels. trouble is the darn engine keeps overheating and the last time i went out inb her we had to get towed home much to my wifes amusement!
what's the cure for overheating jaguar engines guy's? i live in australia"

Well, Dan, I'm certainly not the world's expert, but I have had my share of overheating Jags. There are lots of things really that can cause this condition.
First. One of the first anbd easiest things to check is for proper operation of the thermoststat. Start the car up with the Radiator cap off and let it warm up. See if the water is circulating. If not, Remove the stat from the car and place it in a pan of water and slowly bring to a boil. Before it starts to boil, you should see it start to open. If you have a thermometer handy, you can place it in the water to ensure it is opening at the right temp. If it does, try the next thing, if not, or if it only opens a slight bit, replace it:
Second If you know your thermostat is ok, but still don't see the water is circulating as it should you could have a bad water pump or a blocked radiator. You can take the car into any competent radiator shop to have the radiator pressure tested. If it won't hold pressure, you need to have it cored, or a new radiator. Also, before you do this, look at your radiator cap. If it looks at all worn, replace it.
ThirdCheck for excesive play in the water pump. See if you can wiggle the pully back and forth (especially in and out). If so, replace the pump.

If you try all this and get nowhere, pull your spark plugs and see if they look very white and clean. If so, you are running too lean a mixture which can also cause overheating. Also, check your ignition timing as incorrect timing can cause overheating as well.

This is not a exhaustive list, but should be a good start. Look at the simple, obvious stuff first, then move onto the more challenging stuff. Let us know what you find.

Basil

duntov1
08-25-2001, 04:53 PM
Retorque the cylinder head- first thing!
54 ft/lbs starting in the middle and working your way to the ends!
Richard Wright

Basil
08-25-2001, 05:04 PM
Wonder if that could have been my problem back in high school (72). I had a 67 EType that was notorious for overheating. (The Tan one you see at the top of this page in fact). I had everything I could think of done that seemed to have anything to do with the cooling system - but to no avail. However, I don't think anyone ever thought to retorque the heads (and I certainly didn't know enough at the time to suggest it).

Basil

Graeme
10-09-2001, 07:46 PM
Hi
I Suffered overheating for 3 years in my 4.2 E Type. I checked everything numerous times. Radiator was removed and rodded (cleaned) twice, engine block flushed out, head removed and checked, new fan, thermostat replaced, water pump checked, timing checked, carburation .. you name it was done and all to no avail. The temperature would always climb steadily and soar on hot days - 100C+. Then I had the radiator recored with a heavy duty core. My problems were solved. Sits on 70C all the time now. I can't believe the amount of time I wasted and stress I put up with.

Regards Graeme

Basil
10-09-2001, 10:51 PM
Originally posted by Graeme:
Hi
I Suffered overheating for 3 years in my 4.2 E Type. I checked everything numerous times. Radiator was removed and rodded (cleaned) twice, engine block flushed out, head removed and checked, new fan, thermostat replaced, water pump checked, timing checked, carburation .. you name it was done and all to no avail. The temperature would always climb steadily and soar on hot days - 100C+. Then I had the radiator recored with a heavy duty core. My problems were solved. Sits on 70C all the time now. I can't believe the amount of time I wasted and stress I put up with.

Regards Graeme

Hi Graeme, welcome to the forum! When I was in High School, I had a 67 E (the Tan one you see at the top of most pages here). Anyway, I always had overheating problems too and like you tried everything. I finally sold the car and I often wondered if the radiator just wasn't up to the task. I am currently restoring a 67 OTS and am thinking about going ahead and installing an Aluminum radiator (like from Dan Mooney at Classic Jaguar). Might save be a ton of headaches in the long run - but they ain't cheap.