Strange overheating problem

[dangerousprince]

Hey guys and gals

I have two issues that I can't get my head around.

On long journeys (say from the south to central London) my TF overheats in traffic. It's okay when you're driving but in the queues, the fans go on and shortly after (say 5 minutes), very quickly the temperature gauge goes past the central line (or just below that, where it should be). Not fun stopping between two main lanes in London rush our traffic!

My other issue is that my coolant light keeps coming on. It does go down in coolant a little bit (not by very much - like when my head gasket went) but a centimetre or so. Obviously when this first started, I was paranoid and kept checking it, but its as if the pressure inside is too much which puts the light on. When taking off the cap (when warm) lots of coolant spilt out (when this first happened on the way to Thrope park).

I had a very slow leak a few months back (about 6 months) and used some stuff from Halfords which you pour into the coolant, it goes around the system and fills in any gaps/leaks supposedly. And it worked! For 6 months, the coolant was absolutely fine. I don't know whether this can cause any blockages within the system but wouldn't understand why that would happen 6 months later. Thought it was worth mentioning.

This started doing it about 2/3 weeks ago after a trip to Thorpe park when the coolant light came on a quarter of the way (this is when it first started). We stopped at a pub, let the engine cool down and topped it up with some Hilton water.

I've been thinking about flushing the system but I'm not sure whether this will actually do anything. I mean - it's loosing coolant, I've tested almost everything: the engine fan works, the radiator fan works (and so does the thermostat) the thermostat works because the radiator gets hot when the engine is hot) and the water pump works because I can see it doing a little wee wee on the right hand side when you take the cap off and the engine is on. I get the idea that it's building up pressure, which relates to the cap but I bought a new cap about a year ago. Why would this stop working? That's the only thing I haven't tried, other than flushing the system.

Any suggestions? Other things I could/should test out?

I can do small journeys, but don't trust it to drive anywhere further than 20 miles without an hour break and coolant stored in the boot! In the mean time, I'll buy a new cap but that doesn't explain why it would be overheating.

[steve1951]

Coolant caps are prone to fail, and the more they are removed the more likely it will. Try checking the level with a torch through the wall of the bottle.get a new cap or refit your old one.

Have you bled the system as it sounds very much like you have air in the system,

also I am unsure what you meant when you mention the water pump doing a wee wee, if it is leaking that is your problem........ Ah just worked it out, the coolant recycling back into the bottle on the right hand side, still check your pump, it may be moving the coolant around the system, but could still be leaking from the gland. The pump doesnt create pressure its only an impeler type, the pressure is caused by the coolant heating up and expanding.

I assume, you mean K seal or similar, Cooling system sealant. the jury is out on this, but general thought on here is that its a deffinate no no.

[Sue&John]

Looking on the bright side it may be a minor leak from a hose etc. Try pressurising the coolant system when cool by bodging a tyre valve into a spare coolant cap and pressing up to 10 psi. This will show any minor hard to find leaks when you inspect the system. Minor leaks will only show up when the system is under pressure, and when the coolant is pressurised when engine running will only show as a difficult to spot vapour release. Pressurising the system when cool will show drip drip drip

[dangerousprince]

Originally Posted by Sue&John

Looking on the bright side it may be a minor leak from a hose etc. Try pressurising the coolant system when cool by bodging a tyre valve into a spare coolant cap and pressing up to 10 psi. This will show any minor hard to find leaks when you inspect the system. Minor leaks will only show up when the system is under pressure, and when the coolant is pressurised when engine running will only show as a difficult to spot vapour release. Pressurising the system when cool will show drip drip drip

That's genius! I will defiantly give this a go.

[dangerousprince]

Originally Posted by steve1951

Coolant caps are prone to fail, and the more they are removed the more likely it will. Try checking the level with a torch through the wall of the bottle.get a new cap or refit your old one.

Have you bled the system as it sounds very much like you have air in the system,

also I am unsure what you meant when you mention the water pump doing a wee wee, if it is leaking that is your problem........ Ah just worked it out, the coolant recycling back into the bottle on the right hand side, still check your pump, it may be moving the coolant around the system, but could still be leaking from the gland. The pump doesnt create pressure its only an impeler type, the pressure is caused by the coolant heating up and expanding.

I assume, you mean K seal or similar, Cooling system sealant. the jury is out on this, but general thought on here is that its a deffinate no no.

Haha, no I meant the water pump is working correctly. Inside the expansion tank you can see it on the right hand side (where the pipe comes in) pouring the coolant back into the system. Just showing that the water pump works correctly.

I will defiantly buy a new cap and I've taken it off quite a lot. Like I said, I was quite paranoid with it and because it's so foggy, taking off the cap was the easiest option. I will take your advice and use a torch next time. Is there a max/min line on the expansion tank at all? If so, where about is it located?

[Mav666]

The general agreement is that the cap should be replaced every year so getting a new one won't do any hard, I agree that you should do a pressure test, mine had the same thing, was losing a little bit of coolant, which got worse the other day, I as lucky and could see which pipe had failed when I took the engine cover off, but its not always that simple if the dampness has dried up

[david.c]

Water level up to seam/joint.

[spaceoctagon]

It could be an airlock in the radiator, have you tried bleeding it?

[CJJ]

Was it overheating before you added the "Stuff from Halfords"?

[Sue&John]

Originally Posted by dangerousprince

That's genius! I will defiantly give this a go.

Would love to take the credit......but it's a dodge that's been around for donkeys.... I remember doing it on a Cortina Mk 1 in the 70's!

[dangerousprince]

Originally Posted by spaceoctagon

It could be an airlock in the radiator, have you tried bleeding it?

I have tried bleeding the radiator, all was fine.

[dangerousprince]

Originally Posted by CJJ

Was it overheating before you added the "Stuff from Halfords"?

Nope. Though it was so long ago, I don't know whether it's related.

[dangerousprince]

Okay so the new cap is on the way. With the old one, I'm guessing I would just drill a hole in the top and the some how connect a tyre pump to it. Any suggestions/pictures of inventions people have come up with?

[spaceoctagon]

Drilling a hole in the top doesn't work, the tyre vavle has to be fitted to the inner part, as this bit has the seal!

I made one like this!

first remove the rubber seal!
put a screw driver in the hole in the inner piece and twist approx 45 degrees!
made hole bigenough to fit a tyre valve.
fitted a bolt on tyre valve similar to this
removed internal valve from cap.
drilled hole in outer top part to push valve through!
replaced inner part with valve fitted
replaced rubber seal!

[Lee gsi]

Originally Posted by dangerousprince

I have tried bleeding the radiator, all was fine.

What about the other 2 bleed points? All 3 need to be done at the same time to remove any trapped air.

[kedunga]

Check your radiator gets hot all over, these additives can block and clog your system, in a 160 its the oil cooler, in yours id say your radiator could be semi blocked, try a decent flush then refill and bleed, failing that replace cap, maybe even check your prt as these can also fail.

[barkingdog]

Originally Posted by kedunga

Check your radiator gets hot all over, these additives can block and clog your system, in a 160 its the oil cooler, in yours id say your radiator could be semi blocked, try a decent flush then refill and bleed, failing that replace cap, maybe even check your prt as these can also fail.

I dumped some Rad Weld in a Triumph Acclaim once. Totaly blocked the heater matrix.

[dangerousprince]

Originally Posted by Lee gsi

What about the other 2 bleed points? All 3 need to be done at the same time to remove any trapped air.

I checked the radiator all over and every part of it was not. No cold parts.

Anyone has a link/could let me know where the other 2 bleed points are?

[Phaeton]

There's one I'm told near the scuttle plate which you get access via the frunk, the other is on the large steel pipe coming from the thermostat round the side of the engine over the gearbox. I can take you a picture tomorrow if you wish of that one, but not the other as I don't have it.

Alan...

[CJJ]

Originally Posted by dangerousprince

I checked the radiator all over and every part of it was not. No cold parts.

Anyone has a link/could let me know where the other 2 bleed points are?

Have a look here.

http://forums.mg-rover.org/showthread.php?t=333315