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Strange Heater Problem

R

reynolds_p1

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Location
Midlands
Car
Accord 1.8
Hi All,

Wondering if anyone can help with a tricky problem...

I've just bought a 1999 Accord 1.8 Exec. I have a problem with the heater... its not heating!

Even when the engine is fully up to temp the blowers are blowing cold. This might seem straightforward, but thats what i thought!

I've drained, flushed and refilled the system - no difference. The heater control valve moves as you'd expect when the temperature knob is turned. When flushing the system water flows through the matrix and there are no leaks i can see in the system. Its been to the garage and they said the water pump is working (as i'd thought as the car does not overheat) and they replaced the thermostat, this didn't make any difference.

Feeling the pipes the pipe to the matrix seems hot, but the pipe from the matrix is pretty cold in comparison. The flushing did require a fair bit of pressure to pass water through the matrix (hose popped off a couple of times!).

Have been put and done approx 10 miles in the car and let it run for a while and the system does not seem to build any pressure - no idea why this would be? surely it should pressurise? My guess is that there is not enough pressure to move the coolant through the matrix, but im scratching my head a bit now...

Any one got any ideas what could be causing this?

Cheers in advance for any help!

Adam
 
Welcome Adam, sounds pretty obvious to me your matrix is either goosed or there is a blocked pipe somewhere in/around the matrix system.

If it's not obvious from the bulkhead area, time to whip the dash out i'm afraid.
 
F6HAD said:
Welcome Adam, sounds pretty obvious to me your matrix is either goosed or there is a blocked pipe somewhere in/around the matrix system.

If it's not obvious from the bulkhead area, time to whip the dash out i'm afraid.
Click to expand...

Cheers, its not blocked - I can get water flowing through it when flushing the system. Had the dash off and ben into the matrix housing - cannot see any leaks from the matrix or anything to suggest that its knackered.
 
Have you checked if the pipes going through and coming out of the matrix actually get warm (engine side)
 
Shabz said:
Have you checked if the pipes going through and coming out of the matrix actually get warm (engine side)
Click to expand...


Yes, pipe going in gets warm, pipe coming out doesn't. BUT water flows through the matrix when connected to the hosepipe.

Any ideas why the system would not pressurise?
 
Then I suspect your water pump fins are knackered matey.
 
Not necessarily as the radiator fan may be generating enough cool air to keep the engine cool and the weather isn't terribly hot right now either. Similar thing happened on my mums old Micra - the belt driving the water pump had snapped, car never overheated but temp would rise above halfway then go down again. Every time the fan kicked in, it would cool it down again.

It could be the pump is working but a couple of fins have deteriorated and not building enough pressure...

when was the belt last done and what mileage is the car on?
 
probs already sorted now, but had the heaters go on my dads 6th gen the other day, what it was was the heat cable had come off, meaning the valve defaults to stuck on cold.

This is mostly what has happened to yours.
 
Ah there you go then!
 
93 accord said:
probs already sorted now, but had the heaters go on my dads 6th gen the other day, what it was was the heat cable had come off, meaning the valve defaults to stuck on cold.

This is mostly what has happened to yours.
Click to expand...

Agreed with Marcus on this, sounds like the matrix valve is shut to cold and blocking the water flow. I would check that before replacing water pump etc.

You mentioned that you've had the dash off, did you notice any problem with the motor that runs it or is it manual operation?
 
One further thought would be to run the engine and then remove the heater to engine return pipe, to ***ess water flow from the heater matrix.
Also a useful means of bleeding difficult heater matrices
 
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