I'm of the same opinion here.

Cooling system needs to be in perfect order...that should be clear in all cases. Also, have someone else (unless you're capable of course) check the timing, just for confirmation's sake.

Same with the mixture, as if one or both carbs is set too lean, it's gonna run just that much hotter. A laser gauge is a godsend, and is as important a tool as a screwdriver in some cases where there's any question about the running temp...it's become quite handy on a number of occasions for me.

Good luck man, you'll be fine once these issues are seen to...it survived the journey without major incident, shows good oil pressure so I reckon it'll be smooth sailing once it's dialed in.

 

yep, got a laser temp reader gun, but, as usual, had it in the back of the wrong car. ...it's now in the mk2.

so the next time (and there WILL be a next time ) i'm pushing 110C on the gauge, i can probe the engine compartment, probably right at the temp gauge's sensor location on the thermostat housing, to determine the accuracy of the gauge, and maybe while i'm at it, the inlet to the water pump to evaluate the efficiency of the radiator.

 

Considering most Mk2s have 7psi radiator caps (or 4 or 9 or ...), and assuming that your car has a 50% glycol mix and the temperature gauge is reasonably accurate, a reading of 110C is about the absolute maximum you ever want to see. At that temperature, I would be bringing the car very gently to a halt.

 

believe me, that's exactly what i did... then carefully considered my options. and without expressing them again, i concluded that the best course of action was to press on.

as it turned out i may have gotten away with it. yet i would be more than happy to shell out $100 to magically have those main and rod bearing in my hands to assess any damage.

 

I don't think any bearings would have a problem. The risk is more to the head gasket and exhaust valve seats, but the older XK engines are pretty tough. If there are no worrying ticking noises or steamy white smoke, everything is likely to be OK.

 

An engine running hot from a fresh rebuild is a temporary state, and can't be compared to an engine over heating from a cocked up cooling system.

This assumes that the cooling system is in good order with the rebuilt engine.

Besides Huey, if it was over heating due to a plugged cooling system (as well as a fresh engine), it would be knocking and pinging and have fuel vaporization problems; you wouldn't have gotten very far, let alone 900 miles from your trip back.
Even though the car was running hot, it was still able to get rid of the heat _ I can't see any damage being done.

I would retorque the nuts on the head studs though, it's been done I'm sure when it was tested at the machine shop, but with a good drive like that, I would do it for piece of mind, it's not going to hurt.
Once the temp gauge settles around 70 and the engine is fully broken in, I would do it again.

 

Jeff - isn't hot hot whatever the cause? Though I can't say I've had an engine significantly overheat after a rebuild. Definitely agree on re-tightening the head.

 

good to hear... i'm a bit relieved. thanks.

it WAS running a bit better on the third day, much to my surprise, as i had be at about 5000' ASL for the first two and half days of driving. and so when finally down to sea level in the central valley of california where the temps were probably in the 80's F it ran best of all and the gauge was reading below 100C.

will be hunting down why the front brakes are sticking next. will need to pull the wheels off and take a look at the calipers before i do anything else....or i suppose i could start sourcing brake pads and rebuild kits for them, assuming theyr're OEM.

after a quick peruse of the net, looks like all parts, calipers, rebuild kits, rotors are readily available if i need be. and at a reasonable price too!

 

If it were mine and the brake cylinders were in need of replacement, I would consider swapping to later brakes or one of the upgrade kits. The originals work well, but suffer from corrosion and sticking.

 

thanks, i'll keep that in mind.

getting car out my storage facility tomorrow and pulling the front wheels off. we'll see what's what then. i'm hoping the sticking is a consequence of an unpleasant and rare encounter (as related in a previous post) with a hoard of insects.

 

No, hot is not hot, an engine from a blocked rad and/or a thermostat that doesn't open, can't get rid of the heat, that's when damage is done.
An engine creating heat from too much friction on the bores will get rid of its heat through a healthy cooling system even if it's running near boiling, or even a bit above.

My Jag ran so hot on it's first drive, that we stopped, turned the heater on full blast, ran it at around 2000 RPM and splashed cold water on the rad (it was parked after climbing over a mountain pass at a rest stop).
It brought it down to 90 again from near 100.
It was during the summer and we had to run the heater all the time when we drove around the city.
Same with my Bentley, and the TR7, that's long gone now.

 

Look at the reaction valve in the booster first. This have a history of sticking and then that holds the brakes on. Sometimes all it takes is popping the little piston under the reaction valve out, cleaning the bore and reassembling and the problem is solved.

 

i'll search for it first thing tomorrow. thanks.

 

So high temperatures produced by greater than normal heat transfer to the water in the engine due to excess friction, retarded ignition, knocking, or high revs at low road speed are better tolerated than high temperatures arising from an incorrect thermostat, blocked radiator, or failing water pump?

The booster is the best place to start for sticking brakes: apart from the reaction valve, if the vacuum check valve fails, the air piston drys out and sticks. After that flexible brake lines can suffer internal collapse. Are the brakes bindiing all the time or do they free up when the engine is switched off for a while? Look at the various cylinders last.

 

I hate to say it, but it sounds like everything for a good tune up needs to be checked: Timing, fuel mixture, thermostat. For sure it sounds like the carbs need to be balanced if the exhaust isn't even intensity - or make sure all the sparkplugs are actually firing.

It might actually be worth taking out the temperature sender and put it in a cup of boiling water while it is connected to the car and check what the dash gauge says. I have found the gauges to be fairly inaccurate in the past. Mine for example, reads fine up to about 75, and then as the temperature increases the gauge doesn't.

I'd also look to the rack mounts for the cause of the slop in the steering. If you can prop up a phone under the car and take a video of the rack with the wheels on the ground while you turn the steering wheel see if the rack itself moves back and forth or if the wheels move. The rack should not move. If it does, that's bad mounts.

Regarding thermostats that actually close off the bypass port, I ended up making my own. Details in this thread: https://www.jaguarforums.com/forum/m...ostats-260192/ I found it made a very noticeable difference in my cars running temperatures.

 

i have an idea as to how to go about determining if the problem is wear in the rack & pinion or if it's something else, and will check out the mounts when i have the front wheels off to check out the brakes.

i'll be checking the carbs for sync and mixture too, ASAP. and i am curious to see what kind of access i'll have to the carbs, and just about everything else, once that huge extra-large-pizza-sized-double-horned air cleaner is temporarily removed. or permanently removed, as i have a couple of those pancake sized air cleaners that just might fit on my carbs.

 

I think you're absolutely right Jeff. A high temperature with good circulation of coolant isn't nearly as risky as it will keep temperatures more uniform through the engine. The only limitations are that if the coolant boils, it stops circulating. And that the coolant circulation might not be so good to the rear cylinders of an in-line 6. Still 110C must be close to boiling in a Mk2.

 

You're adding more then what I said and lumping it altogether.
All I said was the engine is running hot from it not being broken in, if you want to call that friction, then you may call it that.
Indeed there may be other problems like mentioned here in this thread, dragging brakes, retarded ignition etc...
About the knocking, it wasn't doing that at all, so the cooling system had to be in reasonably in good working order when it was running at 110, or even 90.

High revs at low speed, I don't believe I worded it that way _ my car was getting hot, and we parked it where I ran it at around 2000 rpm with the heater on full while splashing water in the rad to help cool the engine, and it worked.

I'll change your wording here and I will agree with it.

"So high temperatures produced by greater than normal heat transfer to the water in the engine due to excess friction, retarded ignition, dragging brakes etc. are still dealt with a healthy cooling system, than high temperatures arising from an incorrect thermostat, blocked radiator, and/or failing water pump" ?

A car can over heat when there are problems acting upon a given cooling system, or it can over heat from a bad or failing coolant system _ or it can be both.
In Huey's case, I believe the cooling system was in good enough shape to handle what was thrown at it, and granted there may be other problems as discussed here, but I still believe that the car was running hot due to the engine not being broken in yet, I also think that the other possibilities should be looked into; that just makes sense.
His car was not running so hot as too cause knocking and pinging to the point where the fuel mixture was igniting too soon from over heating.

If your car did not run hot after it was over-hauled, I would find that unusual.

And I'll stop here, I don't want to turn this into some long heated argument, you may ask me a question, and I will post to give you an answer.

 

Jeff, I think we are in agreement.

Sorry I wasn't clear. I didn't intend that your or Huey's engine suffered from those things just that they should be less of a challenge to the cooling than failings in the cooling system itself.

I've never had a Jaguar engine rebored so I don't know where the temperature would go. My experience of classic Minis and Alfas is that any increase in running temperature wasn't noticeable, say not more than might arise from fitting a different thermostat grade, certainly not rising to values where the coolant is close to boiling.

At 7 psi, water will boil at 110 to 111C. If the coolant is 50% glycol, that will rise to about 116 or 117C. 110C on a Smith's gauge is a bit close to those values - to the point I'd check the engine and radiator with an IR thermometer.

 

update:

i ran a road test today looking for cause of excessive steering lash (slop). i thought that i would find that it only occurred while driving in a straight line. why? because about 99% of steering wheel direction changes are minor and when traveling in a straight line, and i was thinking then that about 99% of wear on the rack's teeth and on the pinion gear would occur on a very small number of rack teeth and their corresponding teeth on the pinion gear that are used while driving down a straight road. OTOH, there should be very little wear on most of the rack teeth that are not at the center and a similar phenomenon WRT the teeth on the pinion gear. so there should be no excessive steering lash as long as one stays in a constant turn....but that didn't happen, the excessive steering lash, about 1", occurs at all times and wherever the rack was within it's side to side range of movement.

BTW, the rack itself is not moving and all of the bushings are in excellent condition. i will now try to take a look at the universal joints (i think there are two, and as this rack and pinion was probably some sort of kit or custom installation, who knows what sort of jim-quackery went on during the installation) connecting the steering column to the pinion shaft/power steering pump for looseness, as that's another possibility that would explain the excessive lash at all times.

on the overheating front...

had an opportunity to use my laser heat thermometer gun today on the thermostat housing and adjacent intake hose to the radiator. good news! it read 80C at the same time the gauge on the dashboard was reading 100C. in fact, the only place in the engine compartment i could find that was over 100C was at the exhaust runners coming directly out of the head. they were reading a whopping 220-250C.

ambient temps today were about 85F.