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Heater Problem hot then cold then hot etc!!
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Old 20 Jan 2009, 03:23 PM   #1 (permalink)
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Heater Problem hot then cold then hot etc!!

Hi all Ive a Sti V2 1995 Classic. The heater when turned on blows cold then sometimes goes hot then back to cold again. Does this sound like the thermostat sticking or any ideas what it is please.
Thanks all
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Old 20 Jan 2009, 05:41 PM   #2 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Thermostat/air lock maybe, have ya checked your coolant level? they`re sods sometimes to get rid of airlocks in scoobys.
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Old 20 Jan 2009, 05:58 PM   #3 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Hi just checked water level and all is ok there.

Whats the best way of checking rad other then pressing all hoses, and if blocked whats needed a flush??? or shall i run engine with cap off for about 10 mins on drive.

It was in prosport a few months ago @ Manchester and everything was off the car to enable them to replace oil seals etc...

So should this be happening ive not really done a great deal of miles since then...

Thanks again
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Old 20 Jan 2009, 06:25 PM   #4 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Could be just an airlock if they`ve drained system at all.

When ya say everything was off the car-To what extent"everything"


When i refill mine when i change the coolant top up through header tank itself then squeeze top an bottom rad hoses aswell as other water hoses untill i cant see no bubbles in header tank itself when i do it(may take a while)then leave the cap off(out the way)and start the engine,chances are after a few mins will drop slightly though wont be long untill it try`s to overflow if ya leave it,top up put cap on an let tick over with heater on hot.

Let car get up to temp check if heater feels warm as it should turn car off and check coolant levels daily as it settles for 2 or 3 days.

If the heads have been off though could be head gasket issues, is your temp gauge constant when your heaters blowing hot/cold?
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Old 20 Jan 2009, 07:34 PM   #5 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Hi rad and most of front end was off to enable access to replace the oil seals apparently.

As for the temp reading - its always constant were it should be normally.

I will try tomorrow refilling system and running with cap off for a few mins.

Ill post what happens.

Thanks again
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Old 21 Jan 2009, 06:44 PM   #6 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Ok. Filled the headertank and it WAS low.

Took it for a spin - the heater got hot, stayed hot then the engine started to steam like it was overheating. There was a bit of water splashed to the left of the headertank.

I left it for a while and then took it out again. Looks like it may have just been filled up to much by me.

Ill keep my eye on it for a few days and hopefully it'll be ok.

Thanks for all replies
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Old 22 Jan 2009, 09:57 AM   #7 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Bummer!!!

Just been out in the car and I checked the water level first.

The heater is stone cold again..???????????????


Anyone got any ideas what to do next????

The top hose is hot - the bottom was warm

The temp gauge is on normal temp!!!!!



Thanks again
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Old 22 Jan 2009, 10:37 AM   #8 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Did the fans not cut in then at all and what was the gauge reading when there were steam everywhere in the red or normal-just trying to guess as to wether its a fan switch problem or the more likely(maybe anyway)leak from either header tank or somewhere close thats causing an airlock possibly.

You cant actually fill the header tank itself up too much really as it should run at full permanently(header tank=metal one with rad cap-not plastic top up one nr battery for anyone reading this)


Hard to diagnose anything when the cars not in front of you-sorry mate im trying

If the car did overheat though an theres no leaks/air locks would look at thermostat next however ive never had a problem with a stat on any car ive owned and the intermittent hot/cold heater makes me think water is flowing round ok-gonna text a mate who`s a mechanic to see what he thinks

i`ll be back.
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Old 22 Jan 2009, 10:51 AM   #9 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Mate says airlock If he`s wrong let me know so i can never let him forget it !!
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Old 22 Jan 2009, 11:31 AM   #10 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

HI no the fans didnt cut in as it was running at normal no were near the red.

Ill try to fill the header tank up again and leave to run for a while with no cap on again to see if air lock disappears.

If thermostat was knackered would the temp gauge read either top or bottom not normal.??

Will this get rid of air lock or is it best to flush system and start again.

Cheers
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Old 22 Jan 2009, 12:48 PM   #11 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

Been out to the scoob again. Left it running for 10-15mins toppped up the header tank.

Verdict - mmmmmmmm.!! Top hose red hot bottom hose cold but when you squeeze both bottom and top hoses water comes up out header.

Fans not kickin in either!!!!!!!!

Sounds not to good........
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Old 24 Jan 2009, 03:20 PM   #12 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

1. REPLACEMENT OF COOLANT
WARNING:
Never replace coolant when HOT always wait till engine COLD
The radiator is of the pressurized type. Do not
attempt to open the radiator cap immediately
after the engine has been stopped.
1) Lift up the vehicle.
2) Remove the under cover.
3) Place a container under drain pipe.
4) Loosen and remove the drain plug to drain engine
coolant into the container.
5) For quick draining, open the radiator cap.
CAUTION:
Be careful not to spill coolant on the floor.
6) Drain the coolant from reservoir tank.
7) Tighten the radiator drain screw securely after
draining coolant.
8) Slowly pour the prepared coolant from radiator
filler port to neck of filler, then pour into the reservoir
tank up to “FULL” level.
Coolant capacity (fill up to “FULL” level)
Non-turbo AT model:
Approx. 6.9 LITRES (7.3 US qt, 6.1 Imp qt)
Non-turbo MT model:
Approx. 7.0 LITRES (7.4 US qf, 6.2 Imp qt)
Turbo AT model:
Approx. 7.6 LITRES (8.0 US qt, 6.7 Imp qt)
Turbo MT model:
Approx. 7.7 LITRES (8.1 US qt, 6.8 Imp qt)
NOTE:
The SUBARU Genuine Coolant containing antifreeze
and anti-rust agents is especially made for
SUBARU engine, which has an aluminum crankcase.
Always use SUBARU Genuine Coolant,
since other coolant may cause corrosion.
9) Securely install the radiator cap.
10) Run engine for more than five minutes at 2,000
to 3,000 rpm. (Run engine until radiator becomes
hot in order to purge air trapped in cooling system.)
11) Stop the engine and wait until coolant temperature
lowers. Then open the radiator cap to check
coolant level and add coolant up to radiator filler
neck. Next, add coolant into reservoir tank up to
“FULL” level.
12) After adding coolant, securely the install radiator
and reservoir tank caps.
12.Check for leaks.
Try that way that should do it its out off a manual done mine this way and thank god no problems
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Old 26 Jan 2009, 07:41 PM   #13 (permalink)
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Re: Heater Problem hot then cold then hot etc!!

hi if the top hose hot bottom hose cold have tried to check how warm the rad is if cold at the bottom may have a part blockage can happen if rad removed and it drys out to a certain extent then the silt in it goes hard you could try reverse flushing it ie take the bottom hose off and top and connect a hose to the bottom or try a rad flush treatment but dont leave it in for days could some times damage the water pump seal just put it in and try running for half hr
also have a simaler problem on mine heater very good on full heat but if set to halfway on heat starts to blow cold suspect heater valve or ducting but overheating
all the best but suspect you have a air lock some were
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