Renault Laguna I - Phase 1 - Heating and Cooling - Possible fix for cold heater - Page 15 - Renault Forums :: Independent Renault forum

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post #71 of 115 (permalink) Old 1st November 2008
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Unhappy laguna heater matrix

hi, I was so impressed with your ideas about clearing a heater matrix, I with a blocked one , had to have a go . I first put the hose pipe through, this got rid of some brown sludge. I then did excactly what you said about the acid cleaner. I did this about 5 times until the flow was running clear. Now in the very beginning I was having one hot pipe and one cold pipe behind the glovebox. Now after doing all this work I am having 2 cold pipes?? I simply cannot get the pipes to get hot at all, therefore blowing cold air. I wonder if you have any ideas? There is hot flow in the header pipes but very very slow (is it suppossed to be fast) The hot water just doesnt seem to be pushing itself through the matrix. I have opened the air valve but only hot water comes out. have you any ideas . car stuck on drive at the moment.
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post #72 of 115 (permalink) Old 1st November 2008
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Could be you still have an air-lock. Renaults are notorious for it I'm afraid. Try running the engine with the coolant cap removed and keep bleeding. Also have a look for a bleeder on the radiator - usually around the top corners. Sometimes gently squeezing the main hoses can help expel any air.

It usualy takes numerous attempts though
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post #73 of 115 (permalink) Old 1st November 2008
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Sounds like you have an airlock in the pipe. Open both bleed valves (1 top on rad, 1 on the water pipe that goes to the heater matrix). As you topup the cooling system water will first come out of the bleed valve on the rad, when you get water with no air bubbles coming out close the valve. Keep toping up the system and do the same with the other valve. This should get all the air out of the cooling system. Hope this helps
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post #74 of 115 (permalink) Old 1st November 2008 Thread Starter
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If the heater core is indeed running freely with a garden hose attached to one pipe then logically it can't be that.

However...... I did find that new bits of gunk did dislodge & re-block the core fairly frequently at first...... a sludged-up system will have plenty of that ' goo ' elsewhere in the circuit.

Take a few minutes to double check the core IS still flowing.

If so...... the problem MUST be the flow FROM the engine OR the return pipe.

As someone else said above, an airlock WILL stop the flow, but so will a cold or stuck thermostat.

So what do you do?

a) re-check heater flow
b) check water flow from the engine ( heater pipes off) - is there any?
c) if 'b' OK, then check return pipe to engine is clear (hose?)
d) make sure the car is up to temp & stat open
e) Re-bleed air valve - ensure it IS actually clear with a bit of thin wire.
f) if necessary, temporarily 'crack' a hose joint or two to get air locks out.
g) Have known a couple of cars to have such badly worn / corroded water pump impeller vanes that there is almost no 'push' in the system..... i.e. (b) is there a good flow under some force from the output pipe? If a 'dribble' but pipe is clear - suspect stat or pump.

Hope this helps

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post #75 of 115 (permalink) Old 19th December 2008
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Im doing this on a fortnightly basis now. Ive got it down to a tee although rad flush tends to loosen the crud so much it blocks the system and the car overheats.

I can even do a "flush" in the motorway services now using the water hose to fill your washer bottle.

Was driving to Holyhead and IO started to get cold air, the expected happened and the system clogged up meaning the car overheated almost immediatley.

I pulled into the shell garage, unplugged the right hand hose which is easier to handle. (I wear strong grippa glves now) and flushed the system, refilled, topped up with anti freeze.

I'm going to have to do a complete matrix change at some point but dont know whats involved.
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cold , cooling , fix , heater , heating , laguna , phase , renault

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