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Heating issue and coolant loss


Glover
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The car has always had a coolant loss since before I had it but lately I've been getting either no heat inside the car or heat and then it stops and goes cold.

 

Tried bleeding any airlocks becuase when the alternator was changed they said it lost some coolant from taking the pipe off.

 

This morning I had heat but not as hot as usual and the engine looks like this, looks like its from the radiator cap, are they known for causing these issues?? Or if not the rad cap, anyone else had the same issue.

 

Cheers image

 

 

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N/A's have an issue with a core plug in the water pump backing plate corroding and leaking. Plus the pumps themselves can have shaft gland seal failure and water drips out the bottom and the fan sprays it about. Have a garage pressure test it, and fit a new cap as a service item.
I'll have a look at that then!

 

Filled it up this morning with coolant because it was low and I saw a little steam from under the bonnet when I was driving for a few minutes! Got to work and it's used a lot of coolant! It looks like it's come from the radiator cap so I've got one on the way to try first and then eliminate that!

 

 

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New cap coming this weekend. Hopefully this fixes it.

 

Had to top up the radiator with about 2.5 litres of coolant.

 

Found out it was steaming out of the overflow hose and I'm confused as to why the cap would be doing this? And why my temperature gauge isn't moving from where it normally does?

if it isn't the cap, am I looking at the thermostat next or does this have the symptoms of a BHG?

 

Cheers

 

 

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The system as it heats builds pressure and the coolant is pushed out the hose in the filler neck into an expansion tank, when it cools its drawn back into the radiator.

 

If the rad cap seal has failed then the system wont hold pressure, or very little

 

Does the small hose go to a separate tank that is half full approx of coolant when its

cold ?

Edited by Dnk (see edit history)
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Here's another quick tip. I have several N/A head gaskets that I have changed out and most appear to be fine until you drill out the interleave rivets and split the layers, when you then find a split in an interleave shim..... For whatever reason, possibly the infamous core plug leakage in the back of the water pump housing (caused by erosion by water cavitation) causing over heating, the N/A's seem far more prone to head gasket issues then the GTE 2JZ's.

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The OE cap has the one way valve outlined in red held by a plastic rivet. It hardens and breaks and the valve disc disappears into the rad. It then produces the symptoms you describe
My cap seems to look a little shorter inside that this one, Im thinking the spring may have gone. Thanks for the replies, I'll keep this up to date once I've changed the cap for future reference incase anyone has the same symptoms! Hoping it isn't the HG.

 

The temperature gauge never moved though so I'm guessing the engine isn't overheating? Or will it still be overheating and its just not registering on the thermostat?

 

Cheers

 

 

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If the coolant in the head and block is allowed to drop seriously low (and the figures for how much water needed adding suggests you may be in that region at times) then the temp sensor is not surrounded by coolant and is reacting solely to the temp of the casting it's within. This, due to thermal mass, is slow to respond whereas the head combustion and valve areas are perhaps by now blazing hot. Water temp gauge readings can be deceptive with a low coolant level. I'd get a new cap on and have the system pressure tested. Hell, a Chinese Ebay pressure test kit is cheap enough, assuming it has the right adaptor for the rad neck, to buy and DIY it.

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If the coolant in the head and block is allowed to drop seriously low (and the figures for how much water needed adding suggests you may be in that region at times) then the temp sensor is not surrounded by coolant and is reacting solely to the temp of the casting it's within. This, due to thermal mass, is slow to respond whereas the head combustion and valve areas are perhaps by now blazing hot. Water temp gauge readings can be deceptive with a low coolant level. I'd get a new cap on and have the system pressure tested. Hell, a Chinese Ebay pressure test kit is cheap enough, assuming it has the right adaptor for the rad neck, to buy and DIY it.
Would make more sense then! Yeah I think I'll get it to the garage for the pressure testing after if the cap doesn't sort it. What sort of ranges am I looking at keeping it between?

 

 

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New cap fitted (old one looked terrible and was loose it seemed, like it wasnt sealing right)

Still getting steam from coolant overflow hose after getting to temp and driving round the block.

 

The temp gauge in the car seemed to be higher than it normally would (not by much) and it seemed to be a lot more smokey on start up and lasted longer.

 

Possible BHG or look for maybe a leak in a hose or the radiator ?

 

What type of range am i looking at if it get it pressure tested ?

 

Cheers

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New cap fitted (old one looked terrible and was loose it seemed, like it wasnt sealing right)

Still getting steam from coolant overflow hose after getting to temp and driving round the block.

 

The temp gauge in the car seemed to be higher than it normally would (not by much) and it seemed to be a lot more smokey on start up and lasted longer.

 

Possible BHG or look for maybe a leak in a hose or the radiator ?

 

What type of range am i looking at if it get it pressure tested ?

 

Cheers

 

The garage that does the test should be able to tell you if it passes or not. Don't know what pressure they pump it up to, but unless you're doing the test yourself, it doesn't matter.

 

Chris: I have an early NA, no symptoms of coolant loss but should I be looking at getting the core plug changed as a precaution?

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Page C0-18 http://www.mkivsupra.net/vbb/content.php?60-Cooling-System

 

 

 

Have you topped the cooling system up since fitting the new cap ? is the expansion tank approx half full

when cold ?

 

If the Head gasket is blown in such a way to cause steam out the exhaust or up through the rad get a simple sniff test done as it should show there is exhaust gas's in the coolant, very easy to do

Edited by Dnk (see edit history)
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Page C0-18 http://www.mkivsupra.net/vbb/content.php?60-Cooling-System

 

 

 

Have you topped the cooling system up since fitting the new cap ? is the expansion tank approx half full

when cold ?

 

If the Head gasket is blown in such a way to cause steam out the exhaust or up through the rad get a simple sniff test done as it should show there is exhaust gas's in the coolant, very easy to do

 

Yeah I’ve topped it up and the tank is half full. Yeah I’ll have a look at doing that to test it. Think it may be time to take it off the road and plan to get all the little jobs done as well !

 

 

 

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