Ok, officially angry now. Replaced radiator with a performance ally unit set up the same as original. High efficiency air to air auto cooler added. all hoses replaced. New thermostats. Tried 82 and 74 currently. Two new highest CFM rated electric fans I could buy fitted to original shroud all air leaks sealed as well as possible. Checked timing idles at working temp 8deg before and peaks at 22 at 3000rpm. Idle seems to maintain around 80 to 85 deg. If I simulate running revs it quite quickly goes up to early 90's this is via a laser scanner. If I let her settle to idle the temp comes back down to mid to low 80's. Driving has the same affect, but once up she doesn't want to come down. I'm a little lost.... help please. Hot here atm around mid 30's each day high humidity (far North Queensland)


I have recently read an article of a XJS race car 600hp plus running at Bathurst with a quality ally radiator running too hot, Changed to the original reco'd unit and reduced water temps dramatically. This doesn't make sense as the ally unit should dissipate heat far more efficiently than the brass copper unit, but can't argue with the result.

 

What kind of coolant are you using?

 

As long as the temps doesn't keep climbing up-up-up, running 80s to low-90s is not 'too hot' by any means.

Am I missing something? What are your expectations here? Are you expecting the cooling system to hover at thermo rating temp? I'm not sure if any Jag V12 can do that in 30ºC ambient conditions !

Quit worrying and enjoy the car



Cheers
DD

 

I'm using a compatible organic concentrate 50/50 about ratio.

 

I know what your saying, but creeping into mid 90's has me freaked. I also don't understand why my temps are not being controlled better at hwy speeds. The amount of thrust air coming through the front should be offsetting the work load and rpm factor. A lot of cars seem to be running well under the N. Mine is running just under or on the top of the N. This via laser is just under N is 90c on top of the N is 97c.

 

We discussing the 1985 car? What is the dash temp gauge doing? Also where are you measuring the temps; the inlet temp to the water pump is what is relevant in my opinion.
Assuming that there is a problem with the inlet temp, have you changed the water pump along with your other work. If that is failing to pump efficiently it could produce your symptoms.
Second, are you sure you haver the correct type of thermostats fitted, that close off the cross pipe when fully open?
Third, have you removed all the crud from the oil cooler and the aircon condenser and ensured their vanes are not bent over?
Finally, once all this is checked, if no improvement, try this: unbolt the front bumper and go for a spin and see what the temp gauge does, and report back.
Greg

 

Agreeing with all the above.

The stat length is smacking me at the moment. The Jag stat is generally tooooooo short. If that by-pass port does not close 100%, the things you got going on a NORMAL.

I use an 82C EA Falcon (Aussie car for those in other worlds) stat, and have NEVER had issues.

Air in the system, mainly around the stats is next. Drill a 1/8" hole in the stat disc, and mount that hole at 12 o'clock.

Engine block full of mud and gunk, mainly #4 cylinder backwards on both banks.

The air coming IN the front is NOT getting OUT the engine bay. The DUMB foam pad on top of the transmission is #1 culprit here. Next is the missing front spoiler.

Try advancing that timing a few degrees, CAREFULLY, coz the V12 that is retarded by only 2 or 3 degrees WILL run hot.

A couple of write ups I did a while ago might help a tad.

Trimming the timing on a running V12.doc

V12 thermostat fiasco explained.doc

 

One thing to be careful of when using a hand held temp gun. Most have a little laser dot that makes you think that's the spot where your reading is coming from. BUT it's really measuring the area around that spot and the further away you are from the spot of interest the larger the area becomes. For instance hand held pointing at thermostat housing there's a good chance your getting the exhaust manifold also. Be carful with those little suckers a lot repairs have been done for no reason.

 

Yes, 1985 HE V12.
The dash gauge is reading under the N = 82c to 85c then with engine revolutions 2000rpm gauge reads on top of the N =95c these temps were taken with the car stationary.
The water returning to the engine is around 15 to 18c lower than entry temps so the radiator is doing it's job. This was tested at idle.
I have had the car for about 10 months so I don't have any history as to the water pump other than it looks newish and I can clearly see a fresh gasket.
I have changed the thermostats with OEM units (I'm in the trade so I have a Range Rover/ Jaguar supplier as one of my accounts.) I have tried both 82c and currently have 74c in the car, similar results... a tough higher temps maintained with the 82C units.
Having had the bonnet off to replace the radiator I cleaned every part of the front including all coolers/condenser etc.
I might try the bumper off to see if there is any difference.

 

EA falcon thermostats....I'll be. Thanks for the tips, I'm going to be trying one thing at a time to see the difference it makes. Being in country I would be very interested to see what your car is running at in real temp not gauge position.
One thing I haven't checked is the timing marker to see if it's been moved. I had the dizzy fully rebuilt and calibrated by a specialist so I know it's perfect. when I checked it the other day it was 8 degree's at idle and 22 at 3000rpm so even if the marker is out a little I'm pretty confident that it's not running into retard timing.

 

I totally agree, you only have to move the laser 20mm off the intended target and there can be 4/5 degree's c difference.

 

A couple of things from experience.

I bought a new temp sender for my car (spade connector broke off the original one) and found that the gauge ran almost at the top well above the N, coolant temperature taken (with a Calibrated K type thermometer) at the rear RH water rail was around 95°C. This was bought from a Jag specialist as a direct part number correct replacement. I took the sender off my spare 6.0L engine and voila temp gauge back where I would expect between bottom and middle of N.


95°C in a Jag V12 is ok IMHO. I have seen temps in my car at 103°C with
AC running in +40°C heat stationary in traffic, as long as the coolant does NOT boil the system will work. The boiling point of 50/50 at 15psi is about 130°C so event at 103°C there is still plenty of head room. As Greg pointed out earlier its the radiator output temperature relative to its input temp that is important. Jag V12's run HOT (as do most newer cars) this is not an issue unless the temps continue to climb until the coolant boils.

I do believe having a Marelli car keeps the engine cooler as there is no retarded ignition issue. Opening the bonnet a little to allow air flow out of the rear of the engine bay helps to keep temps down, I removed the rubber seal from the rear of the bonnet lip.

Also keep in mind a lot of performance engine builders recommend temperatures between 96-100°C. Oil temp needs to get to 100°C to boil off moisture

 

Hand held IR pyrometers have a DTS (distance to spot ratio) this is VERY important if you hold the thermometer too far away you will increase the spot size (the IR unit measures the average temperature in the spot) and you could be measuring the exhaust as well. And even the expensive Fluke units the pointer is never in the middle of the spot, I have tested a huge number of these and the pointer is next to useless when calibrating these types of thermometers. I use a K type contact thermocouple and a Fluke 187 DMM, this is way more accurate.

 

I'm getting a little confused re the safe temps for an HE V12 some here are saying that high 80's is about the top end of where you want to be to not be risking top end failure and others are saying anywhere up to 100 is ok. With the deepest of respect I don't know who to believe based on I'm new here and new to the V12 motor. I have built a few XK's in my time but the 12 is a different barrel of fish.
I understand about modern car running extreme temps to meet co2 requirements but this is a 30 year old motor.
My L322 Range Rover has a 105c rated thermostat, that is when it begins to open!!!!but it's a modern technology car that's designed to run that kind of temp.
Am I wrong to think that water temp should be somewhere close to thermostat opening temp. As the stat is supposed to be modulating open and closed to regulate water temp.

 

That's exactly what you *want*. Getting what you want is a different matter.

I've owned several Jags including an XJS V12. None of them would hold thermo-rated temp when ambient temps starting climbing over 30ºC. All of them would creep up a bit...sometimes over 100ºC in Las Vegas in August in city traffic :-). Others have different experiences but IMHO the cooling systems don't have enough capacity to hold thermo-rated temp in all conditions. Some cars do, others don't. This is why Jaguar finally jumped on the 'idiot gauge' bandwagon in the 1990s.

Anyhow....

Coolant temperature is only part of the story. Coolant FLOW is the much bigger part. If the flow isn't good to all parts of the engine you can drop a valve seat at 85ºC coolant temp....because of localized hot spots.

IMHO we've (V12 owners) have gotten ourselves SO worked up coolant temp, top-of-the-N, middle-of-the-N, etc etc that we're afraid of our own cars. If you KNOW the flow is good then don't worry so much about coolant temp...to a point, of course.

Coolant temp of 100ºC, in and of itself, won't hurt the engine.

Others will chime in.

Cheers
DD

 

Thanks Doug, saved me some typing.

The stat OPENS at 82c, and 12c later is fully open, and that by pass port MUST be closed, or 30%ish of the coolant will never see the radiator.

Based on that temp alone, no other iffy stuff, the top hose is around the 94/98 mark, the topside of the radiator will be around the same temp, the bottom hose temp (as Greg says) should be ABOUT 15c below top hose temp. This is an industry expectation of a crossflow radiator in ANY car.

Sooooo, at 98c top, the bottom should be around 83c, and that is why the fan sensor in the water pump inlet is an 85c temp setting.

Bottom hose temps are more stable than top hose, and always have been. That is why all thermo fan cars run the fan sensor in the bottom hose area of the system. That is until ECU controlled fans came along, and I lost it in the smoke and mirrors.

Mine runs thermo fans, EL Falcon, and 82c stats, AND a copper brass radiator. On our 2 trips around Australias coast road we did encounted 50c in the NW area, and the temps of the engine varied very little. I have never used or owned a laser temp thingy, never saw the need, you can "smell" an engine that is running HOT.

I have total confidence in my system, and all the other V12's I have sorted over the years. I am very old school, and apparently have a good dose of common sense, and an enquiring attitude, and way too many Jags.

Check those stats, and make sure thay are long enough when 100% open. You are looking for 43mm, disc to disc. That port is 41mm from the mounting flange, and that 2mm will ensure good closure of that port on each side.

 

I actually think from what you describe you do have a definite problem to cure. Revving the car in neutral should have no effect on temps as the fan, if operating correctly, should more than take care of the extra heat, as the load on the engine is very low. If you are revving the car in neutral and the temps are climbing almost immediately, you do have a cooling problem IMO. Under these circumstances, what are the water temps out of the rad? If you have a flow problem the pump may be quite OK at tickover but not as soon as revs climb. If the main fan viscous coupling is shot, ditto. What is the radiator fan situation? If you have the OEM engine driven fan, what is the viscous unit like? If the original, good plan to change it.

In your situation, I would do the following: Thermostats opening at 82 are correct, use these. Ensure jiggle pin hole is at the top of the disc when installed. Bleed car with nose well up on a slope, aircon unit in defrost. Open both caps, fill at centre until wing unit overflows, replace wing cap, continue to fill at centre until full, undo rad LHS bleed screw and fill until water only comes out of bleed screw. Warm up engine like this all caps and bleed screws back on. When engine warm, stop engine, carefully undo wing tank cap and top up wing tank. Replace cap and top up centre spout. Replace spout cap. Undo the rad bleed screw (LHS top) and top up. Start engine bleed screw out and pour into hole if any needed. Replace bleed screw, remove central spout cap and top up central spout again. Iee if symptoms persist. If they do, then:

In your case, you know the rad is good; as long as you have bled the unit correctly (and in my experience having the aircon unit on defrost is essential while you bleed, as is car nose raised); then either the fan unit is shot or the pump is. FWIW, in your situation, I would change them both. Neither item is ruinously expensive.
Greg

 

Ok, drained coolant again.........removed both thermostat housings and removed stats. I have taken Grants advice regarding the stat length. Had some interesting outcomes. The 74c stats I had in where oem Jaguar. Upon doing the boil test I noted that at there extent they just made the 40mm required to close the bypass port. the temp[ required was about 87c. I then tested the stats that came in the car when I bought it. 74c stats did the boil test. they both opened faster than the others and exceeded the required 40mm length by 7mm. This meaning that they will close off the bypass port sooner. I ran the car at idle for about 30 minutes and laser tested the temp. Didn't get over 84c, 32c degree day. I have yet to road test which is where I have had the problem, but seems encouraging. The surfaces of the bypass ports were not perfect, had a small amount of pitting. I believe that the two surfaces would not perfectly seal from new being Ally to S/S of the stat. Fingers crossed for the road test. I don't think I'm over the hump just yet.


I noticed that the retard vac line (aussie delivered car) to the vac advance unit was affecting idle timing even after 30 minutes. I thought it was only for a short period from cold start??? I might run the car with it disconnected and plugged. Any thoughts???
Thanks for the inputs. Russell.

 

OK.

74c is too cold for the HE, that is carby engine temps.

The EFI system could overfuel the engine at those temps.

Forget the vac retard, major pain, even when new.

Some pitting is acceptable, but that disc must seal that port. Our PreHE had pitting, so housings off, cleaned the port face, and applied JB Weld to that face, and then a simple household tap seat refacing tool got the smoooooth surface I wanted after the drying period.

In your area that system is going to have to be spot on, coz the humidity is the killer more than the temps.

 

I agree 74c is too cold for the efi, but the car is running into the high 80's and 90's. When I put the 82c in the temps get more excited. I'm just trying to get the car into reasonable temps whilst I work out what's the cause of the issue.
When you say forget the vac retard, do you mean disconnect it???