Overheating... or not. What else to check?

[page3]

Sorry for the long waffle. I really don't know if the car still has a problem or not!

Took the S out to Duxford today (100 mile round trip). First time I've had the opportunity since all the overheating problems that are supposed to be fixed.

Just to recap- The water pump was replaced (main cause), all hoses checked (one replaced), pressure check, head gasket check, rocker cover gasket replaced (by me), thermostat replaced, fan switch replaced. Both head gaskets were replaced 18 months ago, when I also had new SS manifolds fitted. The radiator isn't leaking and was new 4 years ago.

In local traffic it seems to get up to temperature (lets say 90deg - needle horizontal) and stay there. When I go on a faster road it dips initially (say to 70deg) and then returns to 90deg. The motorway today was followed by some fast A roads and I was doing around 60 or so when I noticed the temperature creeping up - on the white mark just below the red. Not wanting an overheat I pulled over, kept the engine running and checked the obvious. All looked ok so I stopped the engine, left it to cool for a bit and then ran it a bit with the pressure cap off until water bubbled out (which looked filthy). Topped up and went on my way. No reoccurrence of the high temperature issue.

Travelled home slowly, again with the temperature staying fairly steady on 90deg, except the odd dip to 70deg. All fine.

The S really doesn't 'fell right' at speeds over about 80. Difficult to describe and might be my imagination but just doesn't feel like it wants to go faster like it used to. I'm sure it also used to run cooler, especially in this cold weather.

I'm going to check the anti-freeze as I have no idea how much (if any) is in there. Also, the cabin heater fan doesn't seem to go on 'fast' any more. Always been a bit dodgy so might not be related.

Anything else obvious I should check? I'm thinking of taking it in to a different specialist to get everything checked over, but really don't have the funds right now.

Any help appreciated! I REALLY miss enjoying my S but don't seem to have been able to for some time now...

[Barkychoc]

I assume the electric radiator fan is working?
Is the fan belt tight enough? If it is slipping it may not be turning the water pump sufficiently (and if its new it will have stretched and need tightening again).
Water pump - just because its new don't rule it out.
Have you altered the ignition timing?

[GreenV8S]

Did 'the obvious' include a check that the fan was blowing hot air out of the radiator? Was the cooling system pressurised?

Engines don't change temperature by 20C very quickly so quick changes like this make me suspect either you have an air lock or the gauge is not reliable. It's not uncommon to find pockets of air weeks or even months later if the system has been drained but this shouldn't be a recurring problem. Taking the pressure cap off when it's hot is a bad move since it leaves the system unpressurised - this can cause all sorts of problems including pump cavitation.

[page3]

Barkychoc said:

I assume the electric radiator fan is working?
Is the fan belt tight enough? If it is slipping it may not be turning the water pump sufficiently (and if its new it will have stretched and need tightening again).
Water pump - just because its new don't rule it out.
Have you altered the ignition timing?

Radiator fan definitely working. Checked it.

Not sure about fan belt. Will check.

Done less than 200 miles since the new water pump, so it'll better be working!

Not touched ignition timing, but not sure if the mechanic did.

Thanks, all good suggestions to check tomorrow.

[page3]

GreenV8S said:

Did 'the obvious' include a check that the fan was blowing hot air out of the radiator? Was the cooling system pressurised?

Engines don't change temperature by 20C very quickly so quick changes like this make me suspect either you have an air lock or the gauge is not reliable. It's not uncommon to find pockets of air weeks or even months later if the system has been drained but this shouldn't be a recurring problem. Taking the pressure cap off when it's hot is a bad move since it leaves the system unpressurised - this can cause all sorts of problems including pump cavitation.

Gauge has always been fine in the past. I know that doesn't mean it is now though.

System seems to be pressurised fine, and the mechanic said that was all checked. Sounded pressurised when we removed the cap. (didn't know this wasn't advised.)

Would an air pocket cause the sort of symptoms I'm having? That's what I suspect as not driven the car much since the repairs, and this is the longest journey and first time in more than slow local traffic.

Again, thanks for the suggestions - will see what I can check tomorrow.

Edited by page3 on Saturday 27th December 20:12

[Jed-S]

Have you actually replaced the pressure cap? When you removed the pressure cap what was the water level in the swirlpot?

[Barkychoc]

Have you bled the radiator with the little bleed valve on the top corner?

Having thought about it some more my money is on air in the system.

[page3]

Jed-S said:

Have you actually replaced the pressure cap? When you removed the pressure cap what was the water level in the swirlpot?

water level about 1/3 up the swirlpot which is about normal.

For my sins, yes bought new pressure cap but not used it yet as need to get (or make) a rubber insert.

[page3]

Barkychoc said:

Have you bled the radiator with the little bleed valve on the top corner?

Having thought about it some more my money is on air in the system.

not bled the radiator. Is there a proper procedure to do this? Bible doesn't mention it.

[tvrgit]

The swirlpot (the metal pot behind the radiator) should be nearly full. If that's only 1/3 full then your engine isn't full either, and it'll never cool properly.

The expansion pot (the plastic bottle on the bulkhead) should be about 1/3 full when the engine is cold.

To bleed the radiator, you open up the bleed screw on the top right of the radiator, and put coolant in the swirl pot. You'll hear aur hiss out, and then water will bubble out. as soon as water comes out with no bubbles, tighten the bleed screw. Top up the swirl pot as you go - if the water in the swirl pot falls below the height of the bleed screw, it won't bleed!

Fill up the swirl pot (nearly) when you've finished, with the heater control set to "hot", then squeeze the top hoses to the swirl pot, to make sure there's no air in there.

[Jed-S]

page3 said:

water level about 1/3 up the swirlpot which is about normal.

For my sins, yes bought new pressure cap but not used it yet as need to get (or make) a rubber insert.

I's say that's your problem. The swirlpot should be full whether hot or cold. My car used to run with a low water level until I replaced the cap and rubber washer. I made the rubber seal from a mountain bike inner tube and that works fine and the swirlpot is always full.

[GreenV8S]

page3 said:

not bled the radiator. Is there a proper procedure to do this? Bible doesn't mention it.

The radiator is not self-bleeding. If there is air in the rad you're going to have trouble. When the fan is on, you should feel scorching hot air coming off the fans and when you wave your hand over the rad you should feel it is hot all over. Any cold areas at the top suggests you have air in there. There should be a drain point in the top near side corner which you can use to bleed it.

[mycroft]

sounds like problem i had a few years ago , these cars are a problem to bleed and mechanics i have used never seem to take the time to get all the air out . I think my car had an air pocket that sat in the top hose so after bleeding and running up warm i take the otter switch out ( just enough to bleed ) and go through the process again . It worked for me , but as we all know these car have a mind of their own . Best of luck
Only works on later cars with switch tapped into hose .
Dale

[page3]

A couple of questions, which are probably very basic for everyone else.

• Do you all use just water as coolant or distilled water?

• Is one kind of anti-freeze better than another?

• I have no idea how much anti-freeze is in the cooling system, so will buy one of those devices to check it. If more needs adding I assume I can just drain a bit more out the system via the radiator drain?

• Another thread mentioned (gentle) sanding of the top of the swirl-column to make a better seal. Mine does look a bit rusty. Going to get an inner bike tube to do the cap properly too.

• Rather important one this - I'm assuming I fill/drain the coolant when the system is cold, then run up to temperature and let cool, then repeat. Correct?

• When the pressure cap is off and I run up to temperature, I get water bubbling out of the system. I believe this is a quick way to remove air that mechanic sometime use. Others have said it isn't advised and yet others have said water bubbling out is head gasket failure! I'm not intending to drain this way, just interested.

• My internal fan is only working on 'low' setting. It used to occasionally do this, but if I waggled it then it would go to 'high'. I'm thinking this is probably just a bad connection, so intend to remove the switch (assume I need to remove the centre console unit) and clean it up. Should I always disconnect the battery when doing anything like this and is this the most likely problem?

So many questions!!! Thanks everyone for taking the time so far. Also TVRgit, you blog is simply fantastic! I know these are all simplistic questions, but gotta learn sometime...

[tvrgit]

page3 said:

A couple of questions, which are probably very basic for everyone else.

• Do you all use just water as coolant or distilled water?

Ordinary water

page3 said:

* Is one kind of anti-freeze better than another?

Not in my experience

page3 said:

* I have no idea how much anti-freeze is in the cooling system, so will buy one of those devices to check it. If more needs adding I assume I can just drain a bit more out the system via the radiator drain?

There is no radiator drain. If yours has one on the bottom of the radiator, it's the wrong radiator. To drain, you need to pull the bottom hose off the radiator,

page3 said:

* Another thread mentioned (gentle) sanding of the top of the swirl-column to make a better seal. Mine does look a bit rusty. Going to get an inner bike tube to do the cap properly too.

Good plan. Sanding definitely helps

page3 said:

* Rather important one this - I'm assuming I fill/drain the coolant when the system is cold, then run up to temperature and let cool, then repeat. Correct?

Correct. Make sure the heater control is set to "hot" when draining and refilling.

page3 said:

* When the pressure cap is off and I run up to temperature, I get water bubbling out of the system. I believe this is a quick way to remove air that mechanic sometime use. Others have said it isn't advised and yet others have said water bubbling out is head gasket failure! I'm not intending to drain this way, just interested.

Sounds like a good way to get the system to boil and INTRODUCE air bubbles in inaccessible places, not remove them. Running the system unpressurised can lead to other problems as somebody posted earlier. Unless you know and recognise the difference between a cooling system blasting water everywhere just because it's unpressurised, and blasting it over a slightly wider radius under head gasket pressure, it's a pretty meaningless test.

page3 said:

* My internal fan is only working on 'low' setting. It used to occasionally do this, but if I waggled it then it would go to 'high'. I'm thinking this is probably just a bad connection, so intend to remove the switch (assume I need to remove the centre console unit) and clean it up. Should I always disconnect the battery when doing anything like this and is this the most likely problem?

If you mean the heater fan, then that's a different problem to overheating. I wouldn't disconnect the battery, personally, but then I know what bits shouldn't be allowed to touch other bits without half a fire brigade standing alongside. I would fix the overheating problem first (which is a fundamental "can't use the car till it's fixed" problem), and then fart about with the heater fan switch later.

page3 said:

So many questions!!! Thanks everyone for taking the time so far. Also TVRgit, you blog is simply fantastic! I know these are all simplistic questions, but gotta learn sometime...

AT least now you know you're not the first to be driven up the wall by problems with an S!

[jimed]

I can't add anything beyond the wisdom already given except to say its air in the system and sort the antifreeze asap. I do echo Jed's info that the swirl pot should be full as the water should expand into the header tank when it gets hot as it blows the expansion cap on the swirl pot and then it sucks back as it cools - the rubber gasket (from a bit of inner tube) on top of the swirl pot does help here or you will always lose a bit of water and wonder where its going. If you have any silicon hoses on do recheck they are tight as they need to be tightened a few times until they finally settle down.
Jim

[page3]

Will be doing this later today as no time right now - family commitments.

I did have time to pop out and get antifreeze etc. Tester says not enough in the system.

Also bought a new pressure-cap as the one I already bought doesn't have the rubber gasket and a new one was less than buying an inner-tube to make one! However, the new one says '13', the bible says '15' (as does the first one I bought) and the one on the car right now is marked '14'!

I believe 15 is correct, so going to move the rubber gasket from the one I just purchased to the other new one.

[GreenV8S]

Plus or minus one or two psi doesn't make much odds. Just make sure that the pressure cap is the right length for the neck it's fitted to, and that both seals have a good clean face to seal against. If the blanking cap :canofworms: is under pressure then make sure that seals well too. And if the hose connecting the swirl tank with the header tank is under pressure, make sure *that* is sealed too.

[page3]

Just done as much as I can for today, family commitments and freezing hands got in the way...

• opened bleed value (weird that it is UP for closed, down for open). Didn't hear any air escaping.

• Put in around 2 litres of water/anti-freeze into swirl pot. Closed bleed valve as soon as I saw water, which was almost immediately. Definitely was lacking anti-freeze.

• squeezed all hoses to swirl pot. Did get a big air bubble.

• replaced pressure cap with new one. The old one did look rather rusty and rubber perished. Sanded down lightly the top of the swirl pot which had flaking rust/red hammarite.

• checked expansion tank cap. Looks rusty so cleaned it up as best I could and refitted. Put in a small amount of antifreeze/water mix in here too.

• Left car on idle for 20 mins - temperature had only got to around 70deg by this point, which isn't unexpected given the outside temperature.

• took car for a 20 minute drive locally. Finally temperature up to horizontal (I assume this is 90 deg. Never been sure if the white mark indicates 90 or the needle horizontal?).

• peered everywhere with a torch to try to spot any leaks. None found.

• finally temp rose (very slightly) above horizontal, the fan kicked in for a minute and temp gently reduced back to horizontal.

Now run out of time so will let it cool overnight and then check levels tomorrow.

[jimed]

Glad to hear its all starting to look OK Adam. You will need to top up the swirl pot and also ensure there is about 1/3 in the header tank when cold. Check this again a few times after you next use the car as it may take a small number of runs to get it settled down finally but hopefully you should have got most of the air out now.
Jim