Well, I mentioned just a week ago that the cat was running like new ... obviously she did not agree, and today she caused the first serious trouble in almost 3 years.

It is bloody hot here, around 38C/100F, and I noticed the last 2 days that the high speed fan came on after parking her in the garage after 2 short rides.
So I had Torque Pro on coolant temp all the time.

Today, I took her out, and after some 20 min mountain driving, I saw the temp rising, quickly going up over 110C/230F.
I stopped, opened the bonnet, and heard some gurgling sound on the left side engine bay, followed by a small 'explosion' of coolant a minute later.
After that, the expansion tank in the left wheel tray emptied itself over the road.

The cat is now back in the garage, cooling down, and if I have time, will do some investigative work on the thermostat and the waterpump.

However, how about the lower expansion tank?
Does it have a relieve system to pop at a certain pressure or overfill?
How are my chances this tank, or a hose to it, is the cause?

Car has done 70k miles, is in excellent condition.
The hoses were replaced 2 years ago together with fresh coolant, and the hoses on the upper tank are crossed as they should be.
The only leak I noticed seems to come from the lower tank, but it is hard to see exactly.
I just filled the system and ran the engine for a couple of minutes to see if all the valves are still in place , and noticed no more leaking at lower temperatures, but the temp rising fast.

 

In any car that's overheating is turn A/C off (assuming it's on) and heater on full blast. The secondary tank is not under any pressure ever. There's even a 1/4" or so size hole on the front of that secondary tank to vent out. If you don't have a metal impeller water pump, get one along with a new thermostat. Those are the two cheapest and far superior ways to protect your engine.

 

That was my understanding, my motorbikes have the same system, just more visible.
However, It really burst out (with a fountain of coolant upwards), and I forgot to say, when the engine was initially cooling down, the hoses slowly shrinked due to vacuum, only going back to the original shape after I opened the top tank cap.
That tells me there is something not functioning on the secondary tank, as it should suck coolant back, or air if no coolant remained, right?

Thanks and yes.
I had the waterpump inspected 2 years ago, the garage said it was the new type with the different seal, but I guess I want to see it for myself this time.
And the alloy thermo housing was waiting to be installed, my bad .

Now reading all previous threads on this subject ...

 

I am just thinking a bit more, as I don't believe in coincidence.

I had the oil + filter changed just last Monday.
During that, the c/e had the cap of the coolant header tank opened, I guess to check the level.
I noticed that, as there was some green coolant all over the place due to the warm engine.
If he did not close that cap tight enough, will coolant spit out from there, or can it create a situation like I experienced since then?

 

If the cap is not on far enough the I believe system will not pressurize and the coolant will escape to the atmospheric tank. That does sound like a reasonable explanation for your overheating and coolant release.

 

You stated in your original post that the hoses were collapsed until you open the coolant tank cap.That would indicate the cap isn't the problem. I think its time for you to get the new thermostat tower installed with a new thermostat.
I think the old one is not operating correctly. Once the temp got to high the system pressure went up and the cap vented to the overflow tank. If the cap wasn't sealing the overflow would be all over the engine and coolant tank.
The overflow tank is not sealed and any excess fluid will escape.

 

I overlooked the collapsed hoses, but that makes me wonder about the cap. As the engine cools, coolant should be drawn back from the overflow tank by the low pressure in the engine. I don't think the hoses should collapse if the cap is functioning correctly.

 

Thanks all, really appreciated, it always helps to get some professional input while trying to get my own thoughts organised.
I also came to the same conclusion that the cap can't be the problem in this.

After checking the top of the secondary tank last night, all looks OK there.
I never knew the hose is just hanging in the tank, even a little loose fit, which allowed the burst of coolant upwards while filling rapidly I guess.

I will replace the thermostat first, and check on the waterpump in the process.
The upside is that it the perfect occasion to also clean the heater core, which is stuck for years already.
I never came to do that as the climate here doesn't really require heating other then just some days.

Work to do ...

 

I know you said yours has been changed but, the real problem concerning the waterpump is this... The original WP that came on all these cars had an impeller made of plastic and were mounted on a metal shaft. When the engine reached operating temperature, the plastic impeller could at some point slip (because plastic has a low melting point as opposed to metal) on the metal shaft causing low coolant flow which raises the temperature in the system which also causes the coolant to expand more because of the heat. However, most replacement WP's today for this engine still have a plastic impeller. When I bought a perfectly running 21K mile 00' XJ8 back in 13', I had it towed to the house and the very first thing I did to that car was put a metal impeller waterpump on it. Unless the shaft seal goes bad, I'll never have to worry about it for awhile. I bought that pump for $50 at Coventry West. I even have the same pump on my 98' XJR. For such a cheap price, just assume it has a replacement plastic impeller and buy one with a known metal one while you're doing the aluminum thermostat housing.

 

Thanks for your advice, will take the present one off while being there, and see from there as u mentioned.

EDIT: Now I will have the system empty, how useful / advisable is it to run a coolant cleaner through the system?

 

1. WATERPUMP
Got the waterpump out. It has the alloy packing, and the black impeller, and if I am correct, that means it is the first generation pump, correct?



The impeller is in one piece, but the shaft turns rough, looking like the bearing is shot. I remember to have sometimes heard a metal sound coming from the front while driving up, out of the parking garage, and this could confirm just that.
I will order a new pump.

2. THERMOSTAT
Just tested the old one against a new one. The old one refuses to open,where the new one perfectly does.
I guess the problem is found.

3. THERMOSTAT TOWER
I looked for 2 hours to find the correct tool to remove the rear 2 bolts of the plastic thermostat tower, but to no avail.
So decided to break it down, which was not a whole lot of work.

However, one of the bolts gets wedged against the front of the intake manifold. I think it is free of the thread, but simply cant go further up, and I am careful with putting a lot of force on it so far.

I hope anyone's got an idea, cause I am not really waiting to remove the manifold, which was just done 2 years ago with all new packings.

The car is parked in the shared underground garage, without power or air, so cutting it off might be difficult.

 

Did that water pump have a thick aluminum gasket on it? That looks to have an early replacement water pump as you stated if not the original pump. However, when I took the original one off my wife's 00' XJ, it had an off white color plastic impeller. So yours may not be original but certainly in need of updating. Certainly contributes to the noise you've been hearing. I can't be for certain unless you know how all the other pulleys feel.

Glad you found your problem with the thermostat.

The thermostat housing is a little challenging. I use a Snap-On 8mm swivel socket. It's a chrome 1/4" drive, short little guy that gets right in there. I use a curved hemostat to carefully finish taking those back two bolts out. If you can't get access to those two tools I mentioned, then you need to pull the intake.

 

If you search all the thermostat tower threads, you will see every now and then some of the rear bolts are too long -- you will have to raise the manifold. Occasionally these long bolts can be levered sideways if there is very little thread contact. But since you have removed the busted tower remnants, my guess would be you need to raise the manifold (or dremel cut the bolt heads off!).

Putting them back in is a real treat: use the shortest bolts from the thermostat housing and cut screw driver cuts in the bolt heads with a hacksaw or dremel tool: then you can screw them back in. I must have bought every damn 8 mike mike or 5/16 wrench or socket made to find one thin enough: nothing worked. Screw driver did; gets it tight enough that a few 15* throws with an open end wrench tightens it enough on the gasket. There are also some ball socket bolts available.

Don't forget to replace the cross over pipe, as well. I don't know what water pumps are available in the ROC, but I found the AC Delco to not leak. My first replacement never was water tight.

 

Thanks for the reply.
I never read on that particular problem, but nevertheless, nothing I can do about it anyway.
Do you think I will be alright with the intake seals if I just lift the front of the manifold a tiny bit to let the bolt out?

On the water pump, I saw some discussion on AC Delco and Airtex.
I guess I will fly it in if I can't find it locally, just need to make the decision on these 2.

 

Why not replace the thermostat tower bolts with cap heads (allen key)? Then you can use a ball head allen key to tighten them.

 

Installing is not the problem, there are several alternatives (shorter bolts, allen head, slot for screw driver).
My problem right now is to get this one out, it is free, but wedges against the front manifold housing.



If I had power, I should just grind the head off, but I haven't.
And I am very careful not to use brute force, and to prevent doing anything I will regret later.
So the question remains on the intake manifold seals if I try to lift the manifold just a tiny bit?
Will they drop out?

I have to order everything overseas, so I better first decide on what I will need.

Anyone any suggestion?

 

If you remove all the intake manifold bolts, you 'should' be able to tilt the front of the manifold up enough to get the last bolt out & same for installation. It all determines if the (2) 8mm bolts back under the throttle body elbow are on super tight or just snugged up. It seems to vary by whoever was there before because your intake gaskets were already replaced once. To answer your question, no the gaskets won't fall out. However, I'd take a peek at them while the manifold is tilted up to make sure they're in place.

 

Thanks, that is the confirmation I was looking for after I read about all threads on manifold removal by now.

Just ordered a new waterpump, some hoses, and a serpentine belt, which all will need a week to arrive.
Perfect time to tackle this little critter, clean up the engine block, flush the heater core, and be ready by the time the parts arrive.

Thanks again!

 

If you were to break the base of the old TST tower out (pliers, chisel gently, whatever), I would bet the bolt will be loose enough that it will bend away to be removed (maybe a half of a thread holding it) so you don't have to raise the manifold. Right now, the base is holding it vertical.

I had terrible luck with the Airtek pump, leaked from day one: switched to the AC Delco, no leaks in two years. You might want to be sure your belt tensioner is good; mine broke at first belt change, order a new one too.

Do the crossover pipe as well; they begin to crumble at this age and miles.

 

Well, this was simpler than expected.
I just loosened the 10x manifold bolts a couple of turns, and lifting the housing by just a fraction let me turn that bolt the last 1/2 thread holding it.

Sprayed the alloy thermostat-tower yesterday, using some satin black heat resistant paint I still had.
Looks like the original plastic one, and will stand out less than with the alloy color.



Now waiting for the rest of the parts to arrive (incl. the cross over pipe as per ur advice).