I'm afraid I can't answer that, I just don't know I'll have to contact the garage Monday morning and ask if it was an original part or aftermarket thermostat. The MAF sensor was replaced because another forum I posted in advised it as a fairly cheap fix, if in fact it was that sensor at fault It now seems not. Although it was a second hand part and looked correct and in order, I guess I can't be sure... Thanks very much for your help, hopefully we're getting somewhere now

 

Okay Sam,

Sounds like you've got a lot going on here. We still don't know if you've got just one root cause (i.e. something causing overheating which in turn causes rough running) or two separate issues. Here are a few random suggestions and questions, in no particular order.

1) Are you doing the work yourself, or having a shop do it? If a shop is handling it, let them deal with it 100%. Don't go changing parts or making adjustments, and then leaving it to the shop to figure it all out when your actions don't fix it. Tell them the symptoms and anything you've done, and let them handle it. For example, you mentioned the fan problem (or is that just a symptom?) began only after your shop did some other work. Did you talk to them about that?

2) Do you still have the old MAF sensor? The replacement didn't seem to help, so you may as well swap in the original in case the new one was worse. Rare, but it happens. See my thread (linked earlier) about my '02 running hot. I had a combination of a bad thermostat and a bad temp sensor. I replaced both, and the two replacements were still bad! Talk about a headscratcher. Which leads me to my next suggestion:

3) Do as little as possible. (My personal motto: As little as possible for as long as it takes...) Don't go throwing parts left and right in hopes of an easy fix. Whatever is going on, you're well past that point of a Hail Mary working out. You (or your shop) will probably need to run some basic diagnostics before trying any more parts.

4) The thermostat: As previously suggested, was it OEM or a quality name brand? Some Chinese stuff is truly pathetic, unfortunately. See the earlier link to my thread on overheating. After TWO bad thermostats, I won't install a thermostat until I can test it first. I would HIGHLY suggest testing the existing thermostat. (I shall laugh wholeheartedly if you insist it's good because it's new...) The test is easy to do in a big pot on the stove. Details in that same link. Gus has a good guide at the following link for replacing the thermostat:


JagRepair.com - Jaguar Repair Information Resource


5) Bleeding the cooling system? Personally, I wouldn't worry about it too much. Just drive the car and keep an eye on the temperature gauge, being sure to run the heater, too. I've had my '02 V6 cooling system open several times and have never bothered doing the full bleeding procedure. I got lost on page 6 where you're supposed to put 4 ounces of chicken gizzards in a burlap bag and swing it 10 revolutions counterclockwise over your head while hopping on one foot. Instead, after about 20 minutes of normal driving, the cooling system seems to settle down and all is well again. Expect to hear some gurgling from the heater and the temp gauge may climb slightly above normal for a minute or two. Anything more than 5/8 on the gauge is too hot, but that little bit to the right of center is okay momentarily as long as it doesn't go any higher.

6) Your battery? A trickle charger ain't gonna cut it. Get an automatic charger with at least 10 amp output. Let it charge overnight or until the charger's little green light comes on to say it's done.

7) You mentioned you've got three more coils to change. Get those done. That could be the root cause of the rough running. Then you'd be back to just the overheating issue.

8) I'm a little confused why the fan is running full bore if the temp gauge is still centered. With the gauge centered, the fan doesn't need to run very fast at all. And the same sensor that drives the temp gauge also sends a temperature reading to the computer. There isn't a second sensor for temperature information. In theory, if the engine is sensed as being hot enough to command the fan into overdrive (for max cooling), then your gauge should also show hot. Remember, the gauge is deliberately inaccurate, as detailed in another earlier post. Use your scanner to monitor the engine temperature. On my '02 V6, 230F is the point where the gauge starts to climb above the center position and the fan runs faster.

9) One last possibility for the fan: When the AC high side pressure is above a certain value, the fan is commanded on for maximum cooling through the AC condenser (at the radiator). Try switching off the climate control system completely and see if that makes any difference. If that doesn't help, leave the climate control off and disconnect the plug from the AC pressure sensor. It's on a vertical tube near the aft side of the radiator, on the US driver's side.

10) Have you done a pressure test on the cooling system? This is basic troubleshooting to verify the integrity of the cooling system. If pressure can't build up normally as designed (due to a leak), the cooling performance drops way off. Be aware it's possible to have a small leak that evaporates quickly and leaves no evidence, but still causes the cooling system to misbehave. My car did exactly that a while ago. A pressure test is the way to go. It will find leaks you can't find otherwise. Test the cap, too. That's very important.

Is that enough for now?

 

Blimey, okay heres where I'm at

Trying to do the work myself. The shop ain't the best it seems so I'm going to tackle it myself. If after everything I do doesn't fix it I'll take it him back.

No, I sold it as a working unit on ebay..

Does the OBD tool I've used not show any helpful info in the images I've uploaded?

That's my next job, I had the shop replace the expansion tank ( that's where all this trouble began when it fractured and dropped all the water.) with a second hand unit. At the time I couldn't find a new one anywhere. I've now bought a new one and want to swap that out before I begin work on the thermostat.

OK noted thank you

This charger took the battery to 12.46 V following 2 days of charging. I will pick up another charger tomorrow hopefully. Will a 12amp output unit do the job? Just haven't had chance to go get a new one yet.

Done.

It stays dead centre once hot but if I'm honest I haven't looked super closely as I'm usually near to passing out due to the heat from the blowers keeping the engine fan off

It doesn't work so I never have it on. It switches on automatically when I turn the heating on I press the button off turn the blower to two bars and heat to high and drive, that stopps the fan engaging.

Cap is a good fit but as I said earlier I'm replacing the header tank but I can't get the bottom clip off, big hands. I can get to it, manipulate the clip somewhat but it's on firm. I'll drain the water and have another yank at it this evening but its not easy for me to get to. The walk through in the FAQ here is now obsolete as all the images have been removed. I just need to know if Im supposed to be twisting pulling out pushing the plastic lugs in and prying off with a big flat head screwdriver...? No I've not presure tested the system.

Anyway that's where I'm up to, stuck on the expansion tank

 

 

Something ain't right. You should be seeing more like 12.6 or 12.7 volts. Are you using a trickle charger? Those are fine for long-term storage, but not for bringing a battery back up to a full charge within one's lifetime. And yes, a 12A charger should be fine.

 

This is the charger, i inherited it from.an uncle ...

 

Go to Halford's or another parts house and purchase a good battery charger. Amazon have one for £45.95:

 

I've pressurised the system and it's looking sound at the moment. I'll go check after lunch but it seems air tight. Should I be running the engine to hot while having this attached please?




It's now charging via the correct charger.

 

This is 50 minutes later, about a 1/4 of a bar lost...

 

Remove pressure from the system prior to starting the engine.

 

It shouldn't lose any pressure as it's a sealed system.

 

sometimes the tester itself can have a small leak. I had one that barely leaked at the hose crimp. Do a soapy water squirt on your tester and double check the seal on the tank connection. The foolproof way to check your tester is to connect it to a test block that is sealed

 

Well I finally managed to get the old tank off, just can't get this to clip in / seat correctly ... Am I just to push till I feel it clip in ? Pushing lots but the angle of attack is restricted ..

 

Make sure the o-ring is correctly positioned. You can also add some coolant to the o-ring to make it slide into place easier.

Pinching the white retainer tabs whilst pushing the fitting together helps too.

 

New header tank fitted, now I'm just running it up to temp .. Fingers crossed 🤞

 

I have a leak. That little jubilee clip is on tight without threading it and it looked like it was coming out from there...

 

Broke the little top pipe while tightening ,I remember the screwdriver slipping. Noticed nothing at the time. I've sanded the crack and applied araldite. I will now go pour myself a long drink and contemplate my navel..

 

Hi,

​​​​​​when you have time watch this video and then look at your fuel trims. You wi l then understand the way to look for an air leak.I

https://m.youtube.com/watch?v=5WnM_NsOtd8

 

Okay, but let's stick to talking about cars...



Have you ever noticed how often we (I) have to ask followup questions? This isn't meant as busting your chops, but I keep noticing that while you obviously know what you know, we don't. Information isn't crossing that invisible border from your mind to ours. The forum doesn't charge by the word. Extra details to help us understand what you see? Always appreciated, only ridiculed on the rarest occasion.

Case in point, this present leak. Did it start only after installing the new tank, or was it possibly present during the earlier pressure test? I'm not quite sure where this connection is, especially whether it would have been disturbed during the tank replacement. I'm not sure whether to congratulate you for finding a long-standing leak, or give you a hard time for causing a new one. See what I'm saying?

 

I've had the best results testing on a cold engine. You can try hot, but most test set manufacturers say not to do so. If you'd like to try it, you have to watch the gauge VERY carefully. Normally the cap will vent to relieve any excess pressure. But with the test set in place of the cap, there is no automatic protection. YOU are the protection now, and you have to watch the gauge like a hawk. If it exceeds the system rating, as marked on the cap, you must be prepared to immediately vent it. Use a rag, as you've got hot coolant under pressure.

For a hot test, let the engine cool first. Connect the test set but do NOT pump it up. Start the engine and let the heat increase the pressure. Typically the pressure won't get too high, with the engine unloaded at idle like that. That's why I much prefer the cold test. It seems to find a lot more issues than a hot test.

I know it's easy to convince yourself of doom and gloom, with stuff like head gaskets or cracked blocks. But what I've almost always found is simple external stuff like leaky hoses or a water pump shaft seal.