KV6 overheating and losing coolant

[Randyjim]

Originally Posted by SD1too

For your next move Jonathan I would recommend another attempt at bleeding but this time following MG Rover's procedure which I have reproduced here.
Note that the expansion tank must be raised and the bleed screw never opened whilst the engine is running.

Simon

I'd also remove the small diameter breather hose from the neck of the bottle while you do this. It's helped me extract a lot of air from the system on a couple of occasions. It shouldn't make a difference, but I've found the drillings in the header tank aren't clean on my car and have blocked up on a couple of occasions meaning air cannot bleed out of the cylinder heads or radiator. In fact the hole that breaks out into the neck of the bottle I've never managed to clear.

[T-Cut]

Originally Posted by Randyjim

- - - I've found the drillings in the header tank aren't clean on my car and have blocked up on a couple of occasions meaning air cannot bleed out of the cylinder heads or radiator. In fact the hole that breaks out into the neck of the bottle I've never managed to clear.

I don't think you should worry. The primary bleed is under the roof of the header tank and out of sight. This vent (No:2 in this image) has a similar bore to the pipe connector and will not suffer any restriction.




It's a different situation with the small drilling the exits in the wall of the filler neck (No: 1 in the image). This visible hole is widely assumed to be the head/radiator vent, but it actually serves a different purpose. Indeed most of the time it's blocked off by the pressure cap. Because it spends most of the time as a stagnant dead-end, it easily silts up.





As you can see, the small hole is drilled at an angle. This makes it impossible to unblock by prodding it radially. To clear it of debris, you need a straight piece of stiff wire (like a large paperclip) with a 45 degree hook at the end. Probing the hole upwards at an angle will more easily shift the gunge.

This drilling is used during a heat soak overpressure (i.e. after a hot engine is stopped). Its purpose is to pressurise the chamber shown yellow and open the relief valve. This prevents coolant from surging under high pressure through the system, up the header tank downpipe and being released explosively from the cap.

TC

[ricebridge]

Originally Posted by T-Cut

I don't think you should worry. The primary bleed is under the roof of the header tank and out of sight. This vent (No:2 in this image) has a similar bore to the pipe connector and will not suffer any restriction.




It's a different situation with the small drilling the exits in the wall of the filler neck (No: 1 in the image). This visible hole is widely assumed to be the head/radiator vent, but it actually serves a different purpose. Indeed most of the time it's blocked off by the pressure cap. Because it spends most of the time as a stagnant dead-end, it easily silts up.





As you can see, the small hole is drilled at an angle. This makes it impossible to unblock by prodding it radially. To clear it of debris, you need a straight piece of stiff wire (like a large paperclip) with a 45 degree hook at the end. Probing the hole upwards at an angle will more easily shift the gunge.

This drilling is used during a heat soak overpressure (i.e. after a hot engine is stopped). Its purpose is to pressurise the chamber shown yellow and open the relief valve. This prevents coolant from surging under high pressure through the system, up the header tank downpipe and being released explosively from the cap.

TC

I’ve been reading your msg over and over... and I still don’t get how that yellow valve in the filler cap works?

[ricebridge]

Update: Let it bleed...

Emptied the cooling system today. Refilled and bled, bled, bled, until coolant was pouring out of every orifice. There was a marked improvement on both cooling and heating, but we’re not out of the woods quite yet. The car still overheats when you, shall we say, exercise a liberal attitude towards velocity regulations. But also when, for instance, going up a lengthy hill at some speed.

So — I still can’t get no satisfaction.

I’ll re-bleed the system once again when it’s cooled overnight, and see if the improvement continues.

[SD1too]

Originally Posted by ricebridge

Refilled and bled, bled, bled ... I still can’t get no satisfaction.

It shouldn't be as difficult as that Jonathan. Once should be enough, provided that you're following the MG Rover procedure which I posted.

You say that you've recently bought the car. Hmmm. Your symptoms are often a sign that Mr. Previous Owner has been adding sealant potions to the cooling system. It's no surprise that these can interfere with the thermostat operation and the worst kind can actually partially block the flow in the region of the oil cooler. Time to remove those non-standard copper pipes for an inspection (and replace with the proper part).

Simon

[ricebridge]

The plot thickens. All clues are pointing in one direction, but which?

Having had some considerable help over the phone from English Car Care (highly recommended!), it now seems that a previous owner has taken the hose that is supposed to go from the engine to the heater, extended it ad nauseam, and drawn it to the front of the car. Where it has then been connected to the hose coming out from the heater...

That's about as intelligent as getting an extension cord, and then connecting its plug to its own outlet, and then wondering why there's no electricity

I bought the car in the Netherlands. My 17-year-old petrolhead for a son's comment when I told him about this latest development in my car forensics:
"Yeah, marijuana is legal in Holland, that's why..."

Indeed. Whoever has been messing around with this car most certainly must have been smoking something seriously unhealthy.

[T-Cut]

Originally Posted by ricebridge

- - - it now seems that a previous owner has taken the hose that is supposed to go from the engine to the heater, extended it ad nauseam and drawn it to the front of the car, where it has then been connected to the hose coming out from the heater...

There must be an inlet connection since there was some heat being produced around your feet. Your other (updated) thread sends us here for an explanation.

Can you draw a simple line diagram of it all?

You should ask a mod to merge your parallel threads. It's awfully difficult flipping between two.

TC

[Comfortably Numb]

I know nothing about V6s. But other cars I have owned that started to overheat with hills, towing, fast driving or other minor extra loading, 2 turned out to be worn/corroded pump impellor and/or bearings - the giveaway being water dripping from the pump when first started, before it got hot, when it just evaporated invisibly. And one other - radiator was half sludged up. What miles has your car done? Many recommend changing the coolant pump with the timing belts, every time.

[ricebridge]

Originally Posted by T-Cut

You should ask a mod to merge your parallel threads. It's awfully difficult flipping between two.

Actually, no. I decided to break out the general discussion about the coolant flow as it was a more general topic, for future reference. That was when I still thought that my Extra Hose was actually part of some hitherto unknown version of the cooling system. In this thread, on the other hand, it's all about my car... I won't be updating the other one from now on.

[ricebridge]

Originally Posted by T-Cut

There must be an inlet connection since there was some heat being produced around your feet. Your other (updated) thread sends us here for an explanation.

Yes indeed. Probably the whole system got heated, including the almost-closed loop (it was connected to the rest of the system via an extra T coupling), and so it eventually spilled over into the coupé. But there was no circulation and certainly no heat conveyed directly from inside the engine.

I'd draw a diagram if I hadn't already started dismantling the system in order to put it back together the correct way. Right now, the hoses are simply dangling in mid-air.