Apparent V8 overheat condition. Applicable to XK8 & XJ8 also

[J44EAG]

Guys,

At Weston Park my 4litre S-type staggered onto the site with an apparent overheat condition in progress. Numerous stops along the way but the three other Co-ordinators with me in convoy were not convinced that the engine was overheating.

The effects seen were a low coolant level and message centre on the dash displaying "high engine temperature" together with a temperature gauge showing a needle deflection fully into the red. The radiator fans were constantly running. Only a fool would normally drive a car with that showing. Hence the numerous stops each time the gauge suddenly went into the red.

Eventually we decided that an overheat was not in progress so continued to the show. Thanks to Tony S, Hugh, and Patrick for their patience and support for those fifteen miles or so.

What went wrong. Simple. The temperature sensor in the top hose manifold decided to die. This permanently lit the dash message centre, the low level lamp, sent the gauge into a fit and switched on the fans. Fuel control issues were also evident. Dave Marks confirmed with his Autologic that engine temperature was reasonable and Bob Bate said he had seen the same thing several times.

So I dove back to Portsmouth with the dash lit up like a Christmas tree. Very disconcerting as I think you might agree. Next day the engine took some persuasion to fire up from cold and stalled a couple of times. The above symptoms from the gauge, lamp, message centre and fans were there as soon as I turned the key. Obviously the cold start fueling didn`t kick in as a hot signal was being read by the control ecu. Hence the reluctance to start until some cranking over fueling had occurred and some heat was generated within the engine. Hence the stalling. I`ve never experienced that before.

Zareef at David Manners was at the show and the next day sent me down a replacement sensor. £13.66 including delivery. Fitted in five minutes, normality has returned. Thanks to Zareef for that.

My car had run 77k miles before the sensor gave up the fight. On the basis of that, you may like to consider changing that sensor on a V8 if the mileage is similar or above. When that sensor fails, the effect is far reaching. Another smidgeon of knowledge to the pool then. Note there is a Dowty seal fitted between the sensor and the coolant manifold in addition to an o-ring on the sensor. Belt and braces anti leak technology!

CIMG0026.JPG (99.77KiB)Viewed 7958 times

Alls well that ends well but it was not funny at all at the time. I`ll put this saga in the magazine in time.

Mike

[Montana5]

One for the book then Mike, glad you're sorted now.

Doug.

[XjRestorations]

A huge sigh of relief there Mike?!!
Zareef is a top fella with superb knowledge of Jaguar parts. He has been my accounts manager for the past 10 years - both with SNG and now David Manners. Very helpful chap!

All the best,
Keith

[JimboV8]

Mike,
Thanks for the heads up and the photos of what it looks like. This kind of information is invaluable in these challenging economic times and well worth the time to write it up.

Kind regards,
Jim.

[jeff1954]

Hi Mike

Glad you got it sorted with no damage done. It was nice to meet you as well.

Cheers. Jeff

[J44EAG]

I`ll add a little more here now.

I had been chasing misfires since November last year. Typically the car would cough and splutter slightly on light throttle on an incline. I`d have to kick down to a lower gear to "drive though" the problem. In addition power and torque would decay as the gradient was tackled. Movement of the throttle pedal was non linear and rather disconcerting.

I tried everything to clear the issue. Cleaned the MAF sensor, ensured the throttle body multiplug was making good contact, changed the plugs but not any coils as I didn`t feel this was the problem. All induction pipe clips tight and nothing else appearing to be hanging off.

Having now changed the temperature sensor, the car is much more tractable on inclines. It also seems happier and more settled. My opinion is that the sensor had been going duff for quite a time. It feeds back to the power control module the temperature of the coolant leaving the cylinder heads which has a bearing on ignition and injector timing and also mixture control. That fact became clear when the sensor failed completely and with a cold engine, I had a devil of a job to get the engine to start. Gauge in the red, low level indicator on, message centre on, fans on etc. In other words no starting enrichment available as the ecu thought the engine was overheated.

Clearly this temperature sender operation and functionality is vital to how the 4litre V8 performs. Strangely, I`ve not read anything on this or other Club Bulletin Boards about this sensor issue before which tends to suggest this failure issue may be a rare occurrence. So there we are. We now know from my experience that such problems can occur and how to fix the issue if it does come up.

Interestingly on P30 of the new July 2012 magazine, I note that Colin Margetson has experienced the issue with his MY04 plate 4.2 XK8 so may be the problem is more common than we have yet seen.

Mike

[oldtimer]

Hi Mike, I am pleased you solved the problem, anything like that, particularly miles from home would worry the hell out of me! Now that you have experienced this defect, identified the 'fix'and clearly reported it, is there a way of dredgeing up this little jem in the dim and distant future.
Is there somewhere in the system that stores this critical information that can retrieved by members. So much useful information is being gathered but the thought of trying to find a particular referance would be a daunting task.
I would love to see a Technical Data Base , by model and divided into systems, containing only specific facts and figures and fixes. Entries to this database would be restricted!
I would be pleased to here your thoughts on the subject - I just hope it is not already there and I simply haven't found it.
Oldtimer

[J44EAG]

Hello Phil.

There is the search facility on the BB section but being a self taught and rather incompetent computer user, my knowledge of how it functions is limited. Perhaps some of the more advanced users could possibly enlighten us please?

I`ve always tried to put my discoveries and fixes under the relevant section of a BB. This tale about the temperature sender I placed on the S-type BB under the heading of "Cooling System". However, it is relevant to other V6/V8 models, so I elected to draw attention to this in the title by saying it was applicable to other Jaguar models.

However, a post I put on this afternoon about MAF sensor failure should strictly have been placed in the "Electrical System" section of the S-type BB. I elected to place it in the "Club Comment" section as it was relevant to most if not all modern Jaguar models. So two ways of doing a similar post but some quandary deciding how to post given the relevance to other models.

I take your point about a dedicated "fix it" library. Certainly something I think we might consider. Paul, Rob, Peter and no doubt others may be able to comment on the idea.

Simplistically, many of the fixes and the surrounding issues I suppose are currently available to us directly by opening the relevant section on your model BB. After that some time might need to be spent looking through the postings listings where it is more than likely that the subject will have been previously aired. Correctly used the "search" facility should help, but as I say, I am something of a numpty with its use to date.

Good points, Phil. Nicely presented and deserving of answers. I`ll put the subject on my discussion list.

Mike

[Montana5]

A FAQ section would be good, similar to what other forums have, however we on the S Type section already have a Technical Articles sub section, so why not use it... and this is the part which will need dedication and time, if someone (Mike ) were to gradually pick out all the relevent and worthwhile Technical problems and answers from all the existing posts, then move the best bits (Moderators rights) to the new heading, or probably better to just copy them to a much larger new post, perhaps with acknowledgement to the original poster, thus building up a library of frequently asked questions. This would also provide the platform for each subject to be added to, ad infinitum.
I would suggest that the permission rights are changed so that only the Moderator can post to this section and everyone else is read only, that way it won't become cluttered with loads of off topic stuff, and the Moderator vets what goes in or stays out.

examples:-
V8 Overheat Condition.
Changing Wiper Blades.
Changing Wheel Bearings Front & Rear.
Replacing Heater Valve 3 & 4 Way.
Resetting Electronic Parking Brake.
etc etc

Food for thought perhaps.

Doug.

[J44EAG]

I must admit, I`d forgotten the Technical Articles section was available.

Good suggestions, Doug. I`ll get onto this shortly once I`ve remembered how to move things. Alternatively, I could rewrite the topics given some of the conversations that may have occurred. I know that topics when revisited change thrust so that could be catered for at the same time.

Keep the suggestions coming, Guys.

Mike

[SDRIVER]

Hi I'm back again in relation to my intermitent overheating problem I mentioned it in my hello post.I replaced the temp sensor in the top hose ( easy done) but one problem was that when I removed the old sensor there was no water leakage at all from the pipe as if the system was not completely full the car has since run normally without overheating at all and now it started again I should say that the heating system was also poor on the day it happened,the guage was going up and down like a yoyo as I put the heating to full Hi and then returned it to a lower setting,it did eventually stop and go back to normal this is making me think I have some kind of air lock in the system.I am not losing any water and have not removed any hoses in a long time,I had a new radiator and heater control valve fitted a few years back at a local jag specialist and had no problems since then at all till now,the expansion bottle has the correct amount of coolant in it, now I'm wondering if it could be a fault with actual pump as mentioned in the thread I also had a new thermostat fitted when this all started now I wonder if its time for a new heater control valve again and how do you clear an air lock in the system in a 4.0L V8.I hope someone can help as its getting a bit annoying now. Thanks in anticipation John

[J44EAG]

Always fill the V8 via the thermostat tower cap above the thermostat nozzle outlet. You will need about a 10 Allen key. Slacken the cap. Fill with hot water when the engine is hot to open the thermostat. Remove the header tank cap carefully. Then adjust coolant level via the caps. Make sure the heater is set to full hot in the cabin. Squeeze radiator hoses to burp out air. Replace the caps. Drive the car for a few minutes watching the dash temperature gauge. Stop and switch off if the gauge rises above the half way point. Let cool for a few minutes and check coolant levels again.

The V8 is a little prone to air locks if you have opened up the system. Just make sure all the air is burped out. Running fans tends to indicate a low coolant level and air in the system. Having owned a 4 litre S-type, I experienced the issue a few times after maintenance.

Hope that helps.

Mike K

[SDRIVER]

Thanks yet again Mike that's a great help I had no idea you could fill the system that way,I have never had to do it before which has been good I suppose.The car is in the air on my drive at the moment after failing its MOT for lower front wishbone bushes worn out both sides and rear OS lower wishbone rear bush showing signs of wear and rust(I have already replaced this even though it showed no sign of actual wear but just looking a bit rusty in parts)and the last thing was hand brake not operating fully drivers side, on inspection both slider pins were completely siezed as was the piston itself so I will be overhauling the calipers on both sides,any advise much appreciated thanks again.....John

[J44EAG]

We have a fair bit on S-type and X350 suspension sections. The early S-type suspension overhaul is here.http://www.jec.org.uk/forums/viewtopic.php?f=200&t=8040

Pre-face lift and facelift S-type suspension overhaul figures in the X350 section because S-type, X350 and XF have the later suspensions which are identical. Several posts on the subject then, in the X350 suspension section.

Those caliper slider pins are notorious seizure items. Rebuild using silicon grease or copper grease on the moving parts. Caliper lever arms also seize with age and neglect. Get the caliper off the car, turn upside down and flood with WD40 or silicon oil. Work the arms until every thing frees up. Place a small block of wood in the caliper to stop the piston coming out. Use a Laser 1413 retraction tool to wind the pistons in and out. Alternatively get a universal piston wind back set from Ebay. There is a picture of one of those kits in the X350 pages in the latest Feb 2018 edition of the magazine. Well worth getting that kit.

Hope that helps.

Mike

[SDRIVER]

Thanks mike I bought a wind back kit from Machine Mart some years back that was listed for jaguar cars only to find when I got it home the yoke was too wide to fit the caliper and allow the screw to be central over the piston so I modified it by cutting the back side down it has worked perfectly since.I was very tempted to buy two replacement calipers from Brakes International,they are not too far from me,would have been £140 approx for the two but decided to refurb myself and bought the kits to do the job but they added up to £85 and were actually dearer than buying on line so not a huge saving after all and when I got home the new slider pins were the wrong length ie too long,the joys of DIY
Next job is to read the thread you have linked to thanks...John