Hi all you decent XJS bro's. I am glad to be part of this site. I own two 1985 5.3 HE's, and hope to have some good conversations and feedback.

I have a real concern here ... I have just had one of my HE's totally rebuilt. it cost 25K plus, and the needle still climbs between N and H.


By totally rebuilt, I mean, engine removed and complete makeover using parts from an 88 model. The back end was also totally replaced with every single thing renewed between the back wheels. EVERYTHING.

The radiator is new. Fan clutch new. On cool days ( like today) the gauge stayed on N for a run of 20 miles. ( I DID NOT SWITCH ON THE A/C )

Do you have any suggestions what I might try?

I read of a similar concern on one post that said it could be the Instrument Voltage Stabilizer, but does this sound fisable? where is this part on a 1985 HE?

Thanx and look forward to the xchange

Rudy

 

You don't have a voltage stabilizer but poor contacts at the printed circuit behind the cluster can cause inaccurate gauge readings.

Is the aux electric cooling fan operational?

Are you confident that the cooling system was properly bled? It's a little tricky on the V12s.

Cheers
DD

 

Thanks for answering Doug ... I've notived you give lots of good advice and I'm honoured

Printed circuit has already been cleaned out and serviced, but I do know it gives innacurate readings ... when bottom of needle is level with top of N the Infa red spot only reads 84 ... half way between N and H, it's 91 (ouch and yeah, that makes me feel bad)

aux cooling fan is operational and I believe it kicks in at 88 since I watched needle and tried to judge about where it would be when temp was 88 and it kicked in at that point

I'm not confident the cooling system was bled properly though I tried to interrogate the mechanic how he did it .... he said he "used the bleed valve on top L of rad" but I still feel there may be air pockets ... HOW CAN I GET RID OF THEM ... since this is a critical detail ... should I Jack the front end up and run engine in 30 second butsts, opening bleed valve to purge?

It almost seems I'm going to have to do this myself since who do you rely on? I'm talking a lot of money I put into this car. Don't want to loose it all.

 

That's sounds about right to me. If we assume (ha ha) that you have 88ºC thermostats and agree that the needle should be about in the middle of the "N" when the thermostats are open, then I don't see a problem





91ºC is no big deal but it does sound like the gauge is reading high. Where are you taking your infra red readings?








Ok, good






It sounds like he at least fundamnetally knew what he was doing. Do a search for the process using my name in the search. I have a couple write-ups somewhere that include a trick or two.

Truth is, even if you're experienced it sometimes takes a couple tries to get all the air out



Cheers
DD

 

[quote=Doug;400990]That's sounds about right to me. If we assume (ha ha) that you have 88ºC thermostats and agree that the needle should be about in the middle of the "N" when the thermostats are open, then I don't see a problem



OK ... theremostats are not 88 but lesser ones ... are they 32deg? these were put in to try and rectify the temp issue



91ºC is no big deal but it does sound like the gauge is reading high. Where are you taking your infra red readings?


I'm taking four readings ... one where rubber pipe comes off heater behind brake servo, second left upper radiator, third, right upper radiator, fourth, rubber flex where coolant exits right hand bank near tansmission filler

Note, there is only about five degrees difference between both upper (L/R ) hoses on radiator ... does this sound unusual? Should I get a new radiator, even through this one's supposedly new. (Maybe its a cheap piece of you know what)

I also wonder if the fan clutch is not really up to par ... when temp is 88 - 91 the blade spins round maybe once, one and a half times ... it's certainly not locked

Should I search "Doug radiator bleeding?"


Thanks again ... I'll always have an XJS

rudy

 

Here's a cut-n-paste on cooling system bleeding from an older posting:




There are different opinions on what works for filling and bleeding. Here's what always works for me. It's not difficult, just messy.

Elevate the front of the car about 8" and then elevate the left front another 2-3" beyond that.

Remove the bleeder plug from the left radiator tank. You'll see an access hole in the radiator upper mounting panel. The plug is some arcane size but you'll find something in your toolbox that fits.

Remove the caps from the expansion/header tank and from the filler pipe at the front of the engine....up there by the A/C compressor.

Add coolant/water to via the filler pipe until it reaches the bottom of the pipe. Start engine, set heater control to max heat. Let it run at idle until it warms up. Peek inside the filler pipe every minute or so and top up as needed.

When the engine gets warm increase the idle to about 1000-1200 rpm (a helper is helpful here...or just wedge a little something in the throttle linakge to hold it sligtly open for a high idle.

Let 'er run and run. Give the upper radiator hoses a few squeezes now and again. Keep checking your coolant level in the filler pipe and top off as needed. Eventually you'll see some coolant coming out of the bleeder. That's good. Wait a while longer and (hopefully) you'll see coolant *really* pouring out of the bleeder. (How much? It's one of those "you'll know it when you see it" things..very messy)

When it's *really* pouring out of the bleeder hole, put the plug back in. Wear some gloves so you don't get scalded. If you can't get the plug back in thru all the gushing, shut off the engine and do it....but I like to leave the engine running if I can. Not worth getting burned, though.

Top off the coolant in the filler pipe...I go right to the top... add a quart or so to the expansion tank, button everything up, and yer off to the races.

 

82ºC probably. That's fine







I'd take the readings at the water rail just aft of the thermostats

Don't get a new radiator






They don't fully lock. 1 to 1.5 turns sounds good.

Besides the gauge reading high is there something else making you think the engine is running too hot?


Cheers
DD

 

Best place to take a reading with an IR thermometer a Black surface like on one of the return hoses, if you take a reading on a reflective surface it will be inaccurate. Also check your thermometer instructions they have a D:S Ratio (distance to spot) this is important for an accurate reading if you are too close or too far away the reading will be inaccurate. This is more important on cheaper pyrometers.

Also according to the ROM both 82°C and 88°C thermostats have the same full open temperature listed as 93°C to 96°C so if it is reading a genuine 91°C this is normal............

Check the resistance of the coolant temperature sensor and the temperature gauge sensor. In my 1989 the gauge sensor is on the RH water rail behind the the thermostat and the engine temperature sensor is on the opposite side. Both sensors measure the same.

You need to measure between the terminals on the sensor.
Coolant Temp DegC_______Resistance KOhms
+20_______________________2.5
+60_______________________0.60
+80_______________________0.325
+90_______________________0.250
+100______________________0.190

You can also apply this value of resistance to the gauge to see where it reads.

Cheers
Warren

 

Yes there is ... The AC compressor makes a howling whining racket everytime you rev, because it's really a low budget type; could this be causing the overheating?

Geesh the horrid noise makes my s..t itch something bad.

My mechanic did a fantastic job of using the best parts from two engines, but it got under my fingernails the way he also tried to make it cost effective and find budget parts .... I've only got to change them in the end.

So my question is two part: can a crappie compressor make the engine overheat and could you advise a quiet / low energy using compressor for an XJS? ( I will need one even if it doesn't cause the overheating since I can't stand the noise ... it's a complete perversion of what I should hear.)

Thanks fo much for your advice Doug

Rudy

 

Thanks for the coolant bleeding advice /steps but logic stops me in my tracks and causes me to ask ... if the caps are off the header tank and filler pipe, won't coolant pour out of them before it comes out of the bleed nipple while the engine ticks over and gets warm?

Also you mentioined, add coolant to the filler pipe ... do you mean the filler pipe on the main radiator near compressor, or the filler pipe on the header tank?

Plus, what level should the coolant in the header tank be when this process is finished? I have heard / read it should not go to the top of the neck ... but the bottom of the (header tank ) neck


Rudy

 

OK thanks so much that's good advice ... but let me ask you something more elementary ... how many degrees should the radiator cool the coolant down?

ie, how much cooler should the coolant be on the top R and bottom hose compared with top L, where it returns from the engine?

 

so you have original Thermostats then?

OE ones are too short and only allow about half the coolant to flow into the radiator, the rest just goes back into the engine.

 

I'm not convinced you ARE overheating







A compressor starting to seize could drag down the engine and cause it to run hotter. I don't think it would put a cool running engine and push it in overheating range.

Sanden amkes a good replacement for the old A6 compressor. Google "modern A6 compressor" or similar and you'll also find some outfit who makes a modernized version

Cheers
DD

 

Nope, not unless the system is over filled







Pipe near the compressor







I fill it about half way


Cheers
DD

 

I can tell you first hand what a seized AC compressor does on the XJS and that is cause a lot of smoke and sparks from the clutch

 

Before it seized, though, did you notice any difference in how it loaded the engine?

Cheers
DD

 

I don't know if doug directed this comment to me or war but the compressor has not seized ... it just sounds like something that could wake the dead howing from a werewolf movie ... these kind of things just have to bug anyone with the taste for an XJS. They're the complete antithesis of Jaguar.

 

No ... nothing like that ... it cools the car but for a certain degree of angst

 

[quote=Doug;401725]I'm not convinced you ARE overheating



I might not be ... but I somehow fear the worst ... when the weather is really hot the IR gauge (front L rad hose ) is around 95 - 95+ ... surely this is waaaay too much????

I'd like to hear your comments on this next thing : .... To try and safeguard against the valve seat dropping (while the engine was being overhauled ) I asked the mechanic to pin the valve seat. Maybe that's not the standard manouvre but it happened.

Another thing ... to reassure myself everything was OK and it wasn't overheating, I took my other 85 HE out to check how hot that got. When warm, it ( the other XJS ) has always run with top of needle on bottom of N ... In 8 yrs it has been like silk, dependable and never left me in the lurch ... not one single time ..... so out if interest I decided to shoot the IV on it and check the temp in relation to gauge.

I was pretty astounded when the front left hose was 91 ... and the metal rail where rubber tube comes out and passes by transmission filler was 100!!!!!!!!

That made me step back ... 100 ... but the car runs, and has always run smooth, with the engine really quiet and healthy. ( its done 110 K orig miles)