Hi everyone - new member here, spent some time reading forums previously. Recently been working on car and having some concerns with potential overheating?? When driving temps fluctuate on gauge, which I'm not positive is accurate or not, from 110C -125C so I suspect that the thermostat is working, but when I return to garage I have notice coolant leak at the top of the cap, there is no overflow tank coolant goes direct to ground from the second hose on the cap and when I park the car I notice coolant dripping out. I ordered a cap from moss the non pressurized cap, pulled the cap from the tank and realized it is pressurized style.

so question are:

Should this cap be pressurized style or not?

Also I see that on my pressurized cap it is missing or never had a rubber seal at the top maybe that is my problem with the coolant at that area?

do I have an overheating problem based on the fact I am getting coolant running through those two smaller hoses? I would assume those are only active when coolant is getting too hot?


Thank you!




the car


caps

temp

 

The system, as originally designed, used a pressurized header tank and a non-pressurized overflow tank. In that scenario the cap at the location you show would be a blanking cap and a pressure cap would go on the header tank.

Since you apparently have neither a header tank nor an overflow tank (thus, an 'open system') , the cap at that location should be a pressure cap....the type without a seal under the rim of the cap.

Foggy memory at the moment as to the two smaller hoses. I recall (at least) one of them being vapor relief.

110C-125C is way too hot for normal running. Something along the lines of 82C-95C is what you're after. Perhaps you have a clogged radiator or stuck thermostat? Or ineffective cooling fan?

Cheers
DD

 

Doug -

Thank you for the helpful information. I did purchase a new thermostat and there is a fan on the radiator but I do not think that is working properly either. Those are my next two items of business to rule in hoping that the radiator isn't clogged....really appreciate the feedback I am having some difficulty interpreting the information that I do find as the engine isn't exactly set up like it was in original jaguar car.

 

1, Wellome aboard.

21. that wure is an nteresting and great looking vehicle. The Jaguar drive train is a perfect fit.

3. Perhaps th new nose is not large enough to allow enough air flow.

4. Bewaarw, Theres engines do not respond well to an over heat condition. Ask if you widh, I have recovered as to my disaester.

Carl

 

Carl -

thank youth nose is small, there is a fan but I need to get it running...car sat for a while, rebuilt carburetors and have it running but the heating issue is present...funny I am also in Walnut Creek CA any recommendations as to a local mechanic would be great.

shaun

 

Wow!!

1.. It also occurred to me that it is not over heating, but yy yjr hisge or sensor is at fault.
2. Joe's foreign auto 4. on N. Main. 3
3. Frank's auto on blvd. Way. The tech that helped me might still work there. Solved an emsion issue on my Cadilad powereed XJ. Not afrad of a "different " carl
4. Use an IFR to read at the point tht the sensor is located. HF has them cheapp.Or Amazon an amzing source of stuff at the front dooor1o

 

Where you have the pressure cap, the housing it's mounted on is just not designed to take it, there should be a blanking cap, and coolant expansion is dealt with at the expansion tank. What you have is a system with no room for coolant expansion at all, hence the leaks.

Whoever installed the engine obviously didn't know about the need for the expansion tank. So why not just add an expansion tank ?.

 

Doug, carl and Fraser - thanks for the input. I am a little embarrassed to admit that I never looked at the other side of the engine bay so my first post had some inaccurate information .

there is an expansion tank, I am the one who didn't know/look around better Haha

So now that this a bit more sorted out a few updated questions:

1. since I do have an expansion tank should I have a blank cap there?e...Do I need two pressure caps one at the expansion tank and one at the manifold location. Or do I need to swap my caps around?

2. the expansion tank is full of coolant ~2" shy of the top, so what I see leaking out when I get back isn't much compared to total volume in that tank, perhaps there is just too much coolant in the whole system and it needs to self level?

3. the fan on the radiator has a single wire leaving it going to the thermostat, assuming the fan is supposed to turn on at certain temp...to me it appears like there is no power to the fan itself if that is the only wire it can't be drawing power from the thermostat housing?


Carl - I need to get the car over to Frank or Joe's but I really don't want to be driving it and have an overheating problem while en-route!


expansion tank blanking cap

expansion tank level ~2" shy of top

expansion tank exists!

single wire from fan to thermostat

single wire at fan to thermostat

coolant tank with pressure cap

 

Very often engines will find their own level of coolant and puke out what they don't want.

I found myself embarrassed more than once when I drove an Ancient Chrysler 440, which I dutifully filled the overflow tank to the recommended level only to leave trails of Green blood in various parking lots after a hot run on a warm day of city driving. It frightened onlookers to Death even though it never ran hot.

I finally learned to just leave it alone where it wanted to be. I had no more problems with boil-overs after that. The tank usually had about 2 inches of coolant in the bottom.

Now I leave all my other vehicles to find their own levels too.
(';')

 

Caughell - The expansion tank should have the spring loaded pressure cap and the cast iron filler assembly should have the non-spring loaded cap. And I think 2" from the top of the expansion tank is way too much. Should be 2" from the bottom of the tank. Others may correct me.

Bill

 

The proximity of that overflow tank to the exhaust manifolds seems bothersome but not sure if that would contribute to your overheating. The red sensor you see on the manifold was actually for an AED (automatic enrichment device) on the older XK engines. It won't do a thing for running your radiator fan as there is no power on that sensor. You need 12V going to the fan on one lead and the other to ground. The fact that there is an engine-driven fan on the car suggests the overheating may have been chronic, hence the addition of the electric fan.

Dodgy wiring can make the gauges misbehave. You can buy an inexpensive IR temp gun and verify if the gauge is reading properly (or not).

 

Thanks for the replies...

going to swap the caps and put the blank at the manifold and pressure cap on the header tank. Since my header tank is so full, and the filler tank on the manifold is pretty empty I am thinking I have passed all my coolant to the header tank and don't have much in the system so before I start it up after swapping the caps around, how full should the filler tank be? Up to the neck where the hoses pass to the radiator/header tank?

 

The header should have coolant just below the blanking cap, ( about 1" from the lip, I think, and the expansion tank should have about 1-2" of coolant when cold. Do you know what year car the engine came out of, because I'm worried you may have a cracked block. This allows combustion chamber gases to pass into the coolant spaces, and force the coolant out. It took me some time before I sorted out this problem on my old 1980 XJ6. Eventually a very nice scottish gentleman who rebuilt these engines as a business told me what was happening.

 

Thank you everyone for all the feedback as I navigate through this. I have an update and more questions.....

1. as stated, I found the header tank that is supposed to be pressurized
2. Swapped the pressure cap from the filler to the header tank and the blank cap to the filler
3. added coolant to the filler since I was low as I suspect what was happening was when I drove around I was just pushing coolant out of the system for good and constantly depleting

Fired it up and idle up to temp. Was checking temp of manifold with an IR temp gun. The left side of the thermostat and then right side of thermostat to make sure it would flow at temp. Temps were ~168F on the manifold when it started to move over to the other side of the T-stat and into radiator. So I let the car idle in position and as expected temp started to climb because no real air flow. Temp at top of radiator was ~140F bottom of radiator ~88-95F going out of bottom hose to water pump. So I took it for a spin see what I would get. temp needle stayed right in the same spot the at distances where before it would climb, so I continued on and ended up driving around for the most distance and speeds I have yet. Seemed to all work great! thank you.

get back to garage, idle some more and check temps everything seems to be fine go and park in the garage and 2-3 minutes later, SPLASH the coolant is all over the floor from the lower radiator hose to the water pump at the radiator connection....so questions now are:

1. am I building pressure in there? or is it just the expansion from heat and shrink when cooling.
2. anything I should be concerned about?

What I plan to do is tighten down my hose clamps and try again...they certainly could have been loose (car has sat for a while) and also wiggled around some. the angle of the hoses and connection may also be of concern? pictures below



underneath view

top view from engine bay

view through grill


Thank you

Shaun

 

Can not tell much from the pics.

1. Is the loewer hose in good condition?>
2, Are both ends of the hose firmly seatedon the spoigot.
3. / Are the clamos tight.


Or, is the leak elsewhere and merely sun lights in that area. i supect the expansion tank hoses.

After shut down, heat builds before it cools, as does pressure.

I am not sure if your system is fully closed or if it can vent to the atmosphere.

Carl

 

OK, here's a key test. Is there any pressure in the coolant jacket when the engine is cold ? (i.e after leaving the car overnight). If there is, check the coolant for combustion chamber products. Head gasket failure is an unfortunate fact of life with these engines, which were, (to be honest) a spatchcock done when the engine wasn't just in middle age, but in its dotage !!

Do you know what year car the engine came out of to fit in your sports special ?

 

@Carl -
2, Are both ends of the hose firmly seated on the spigot. They were, but as your next question suggest, I don't know I didn't check before driving it.
3. Are the clamps tight. This is what i plan to do next, re-attach it all and tighten it so i know that it is tight and then go out and try it again.

@Fraser -
Is there any pressure in the coolant jacket when the engine is cold ? (i.e after leaving the car overnight) not sure, and i dont know how to check that? any advice.

Do you know what year car the engine came out of to fit in your sports special ? No i dont, thats on my list of things to do as well. I havent looked to hard for a serial number on the engine and not sure where to look yet. I did find a number stamped on it but i dont know if it is the right one im looking for. #8L15670

-shaun

 

If you remove the pressure cap when the engine is cold there should be no "whoosh" of air. If there is then something is wrong. The engines with the long head studs are notorious for cracking between the bores, and the only viable solution is an engine strip-down to a bare block, removal of the existing cylinder liners, and insertion of lipped liners so the cracks are covered. This involves a lot of machining so is not cheap.
Later engines were built with the so-called "slotted blocks", that improved matters, but didn't cure head gasket failures entirely. All this took place when Jaguar were about to convert to the all-aluminium AJ6 engine first installed in the XJ-S, then in the new saloon from 1986 onwards.

 

If i am going to test for pressure by removing the cap and listening for air Whoosh, I am assuming since my bottom radiator hose came off after the last run, i will need to re-attach, run car to try again, let cool overnight and then open the system and listen?

• would the pressure be lost since the hose came off?

If i get a block test kit to test for combustion gases in the coolant, would i use it at the header tank location? rather than the fill point on the manifold?

-shaun

 

1. In theory, either cap can be uszed for the combustion gas test. I would use the blanking cap. thus retaining the excess pressure relief feature. Others may differ., If so, i would not disagree. I can see it either way.

2. Another clue as to a leaking gasket is the spark plugs. Ig combustion gas is entering the coolant,. the reverse can also be true, coolant entering the combustion chamber. If so, you have water/steam injection!1 Are any of the spark plugs much cleaner than the others ?

3. Run the gine til it is warm with the header cap off. loook at the flowig coolant. bubbles ??? A mark of gas contamonation

4. What so the IFR numbers reveal?

5. Have you foud a real source of power for the auxilairy fan? Teh one wire in the picture does not do that!!

Car..