Cold V8 - lack of heat

M

Madalicesdad

New Member
In the recent cold weather my 1976 3500 auto has been like a fridge. On the daily drive to work (9 miles of A roads, minor roads and traffic jams) the temp gauge fails to get above 70degc. I've blanked part of the rad with a board, but this makes little difference.
When it does get warm (eg the journey home), the gauge shows a constant 85degc (the thermostat temperature), so I'm pretty sure the gauge is not at fault and the stat is working.
The heater has always been useless, even with a new matrix fitted two winters ago, but the radiator hoses etc feel cool so i doubt it's the heater at fault. There is a leak in the rad but I always keep it topped up.
I'll change the stat this weekend in case it is sticking open, but any help or suggestions would be greatly appreciated, especially by my 13 month old daughter who has to suffer the cold on her way to the nursery!

Mike
 
I would suggest the stat is stuck open, simple and cheep to change, then see how it goes. Does the temperature drop on the motorway at speed ?, if so its almost certainly stat stuck.

What often happens is that the stat opens and closes but doesn't fully close, so you get enough flow to stop the engine warming up quickly.

Richard :)
 
I have to agree with the webmaster - when I got my P6 (also a V8) it took ages until a lukewarm wind originated from the heater. Took out the 'stat, and it was stuck open by a minimal amount - just 1mm or so, but that was enough to have the water circulating. Another possible scenario that I've had with a few other old cars is that the thermostat opens way below it's specified temperature, thus again allowing the water to circulate before it should.

As the non-AC Auto V8s have fixed fans they'll overcool the engine if you thermostat is stuck open or opening too soon, so I'd change it - it's not like it's a hard job :)

HTH,

FC
 
Engine temperature at steady 60/70mph is a constant 80-85deg. I've since checked the stat, it's not stuck even slightly open and opens at about the right temp but I'll change it anyway. If this doesn't cure it (the problem has been happening since I first had the car and this is the 5th winter with it), is it something I have to accept or is there something else I can do? Flatcat - When you'd changed the stat, did the "lukewarm wind" get much hotter?
The flow to the heater is minimal, could this be a blockage in the engine galleries? Can the pipes be re-routed?
Would fitting a hotter stat (winter use only) improve things without detrement elsewhere?

MikeP
 
One more thing, check the heater controls are adjusted properly, make sure that when you pull the control for hot, its actually opening the valve properly.

Other than that, it could be a blockage in the pipes, have you always kept the anti-freeze strong enough ?, alloy heads/blocks corrode and flake badly if antifreeze is too weak or non existent.

Hope this helps

Richard
 
hi,
as the webmaster said, it is usually through lack of anti-freeze. what tends to happen is the heater matrix furs up inside causing a lack of hot water in it. either strip it and re-core it or use a 4cyl heater box, they don't get furred up being they use a steel block engine.

ian
 
The anti freeze is weak (due for change this weekend) but the heater matrix is less than two years old (new, not reconditioned), but didn't give any noticable heat when new! Blocked engine galleries may be part of the problem, but the main problem seems to be the engine doesn't get hot.
I fitted an 88deg winter stat last night, after 20-25mins driving this morning, the temp was still well below 80deg. The hoses to/from the heater box get warm (not hot) and the top hose stays cold suggesting that the stat is sealing properly.
Maybe a pipe has been incorrectly fitted in the past? Does anyone have a diagram showing how the water should flow around the system?
Or, maybe this is as good as it gets?

Mike
:(
 
Mike,
We must be missing something here. The V8 engine produces massive amounts of heat that the cooling system can only just cope with when everthing is working well. The engine MUST be getting hot and it has to transfer this to the cooling water (or sieze solid!) Are your top and bottom radiator hoses getting hot? I cannot believe that your new(ish) heater matrix is furred up but the only V8 car I've had with a poor heater was cured by disconnecting both heater box hoses, draining the water and re-filling with a kettle of boiling water and a couple of kettle de-furring tablets - Leave for 10 minutes and flush out with a hose pipe. refill cooling system with antifreze and water and voila - Perfect heater operation.
Hope this works for you, regards, John.
 
The engine does get hot (eventually), but having looked at the system this weekend, I think the problem is the lack of flow to the heater - barely a dribble comes out of the outlet hose.
Looking at various diagrams of the engine, the coolant into the heater seems to come from a gallery in the inlet manfold. Can this get blocked?
I'll flush the matrix as you suggest and check for other blockages and try again.

Mike
 
Last night, I back flushed the heater with a hose pipe and out of the inlet hose came a lump of blueish crud, about 10mm long/6mm across. Quite a big lump compared to the size of the pipe!
Water flow through the heater improved, and when stationary, the air gets above lukewarm and there is a noticable difference in temp between inlet and outlet hoses.
Unfortunately, when on the move it's not so good suggesting the heater doesn't seal properly and cold air is getting in. It looks like I'm going to have to take it out and have a look.
Thanks for all the help and suggestions.

Mike
 
One thing I have done to help during this weather is to remove the static fan.

Mine has a kenlowe fitted which has'nt kicked in yet. Obviously it needed accurate adjustment.

The car gets nice and warm and should actually use less fuel due to having less resistance and operating at a better temp. It is believed that bhp is improved too!!??

John.
 
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