Heater Matrix

[Dan W]

Hello (again), my cabin heaters are blowing lukewarm, but heat up under revving. Considered water pump issue but rear heater blows hot at idle.
New thermostat fitted recently as well.
So I'm thinking it could be gunk in matrix. I'll post some pictures up when I get home of the pipes that I think supply the matrix so I can double check I'm sticking my hose in the right hole

 

[Chris]

I've got a spare one if you get stuck.

Chris

 

[IRLGW]

mine does exactly the same thing...have tried numerous cans of rad flush but this only works for a few days. You can disconnect the heater flow and return pipes and try flushing just that part of the system which means that you don't have to remove the thermostat. when you flush the whole system the thermo closes again once you add the cold water unless you can flush from a very hot tap! Not sure what year or model your truck is but if you happen to be a 12v manual like me you may want to swop the heater matrix for an aircon one...

 

[Dan W]

Hi thanks for the replies, and thanks for the offer of a spare (I will at sone point arrange to pay you a visit Chris, I want to get all the rusty bits sorted first so it's presentable).
I have a 96 FZJ80 with aircon if it helps? Now I've been having a think on two points (this is normally very dangerous).
First off I dont really know what the inside of a heater matrix looks like, but if it's a hollow tube then is it possible for me to feed a drain*cleaner attached to a pressure washer through it or is this either impossible or could it damage it?
The other thing I'm thinking is, this started after doing a rad flush and coolant change soooo it's possible all the stuff I dislodged has ended up in there. I had the hosepipe up the thermostat housing, rear heater pipes and radiator, this was the only part I didn't do.
So is it possible to fit a coolant filter? I thought I'd have my dragons den moment when I thought of it, but it turns out that coolant filters are already a 'thing'. However they seem hard to come by, mainly off industrial vehicles.
Soooo, what would you guys think to just fitting a diesel fuel filter from a Hilux or something as a coolant filter? Is there something fundamental I'm not seeing with this plan?
Thanks for listening to my ramblings

 

[Dan W]

Although thinking about it, maybe a diesel filter won't work with water. Hmmmm.....

 

[Chris]

Dan, the inside of the heater matrix under the seat is a proper matrix - like a mini engine radiator with fins, grilles etc. No route through with a bog brush. Are you going to 4x4 show on Sunday?
Presentable? FFS, have you seen MINE?

Chris

 

[Dan W]

Hi, I dont think I'm going on Sunday, it would appear I'm booked in for an in-law appointment.
Well I flushed both front and rear matrixes (or are they called cores, I dunno?), and it didn't have much effect, so I thought if the front is blocked then all the water would have gone to tear. So I blocked the rear heater hoses and tried again.
It fetched out some gunk (top tip, a large pond pump is excellent for this task) but it still had no effect on more heat in the cabin.
So been thinking about it, when I reinstated the rear heater, I replaced the corroded pipes with rubber hoses that have a larger internal diameter than the metal ones they've replaced. So maybe the coolant is taking the easy route, through the rear heater instead of the front.
I'll install a valve in the rear pipes to slow water flow down and see if that works.

 

[Dave]

Have you checked the hot water valve on the bulkhead, and the flaps on the heater box.

 

[Dan W]

Yup they're all good thankyou. Before I try the valve thing I'm going to find a steep hill to park up and see if that can get any air out.

 

[Roy Duffy]

I don’t know much about these things, but you could try blanking off the under seat heater pipes. Then you would be getting all your flow through your main matrix, and that may point to the replacement pipes being to large a diamater. Im just about to blank off my underseat heater as i have rusty pipes too...