How do I unblock a laguna blocked heater matrix?

I have a 1997 Renault Laguna 97rt. The heater matrix seems to be blocked. Bottom pipe into heater matrix is scolding hot but top pipe coming out of unit is cold. Does anyone know how to fix this problem? Would a coolent flush work?
Sean Hall, November 2004


done
hi i have a simmilar problem on my nissan almera. system has been flushed many times. have reversed the heater pipes. this seems to be working. also have a flushing agent in as well. im starting to get warm air in the car now. so fingers crossed. pete

peter, December 2010
I have a renault lagina 1.8RN with the same prob (very common), I did the same as Alison but it was being stuban so in my annoyance (and unwilling to give any more money to renault) I brought some powerful drain cleaner (made sure it was O.K for Metals) and sat the matrix upright in the sink and kept pouring some in let it soak over night then used the pipe from the shower (for pressure) to flush it, took a few times but its the cleanest it ever been.

ste, February 2005
Have just removed my heater matrix from my renault 2.2rttd It was blocked solid. It took a lot of time and patience but With warm water running out of kitchen tap shaking it and emptying Many many times its slowly freed. Once it was starting to work mixed a solution of soda crystals and boiling water poured in and left to soak for ten minutes then flushed and shook again several times Did soda crystals again left for 30. mins and flushed again. Its taken about two hours playing and flushing but it works now and total cost nothing half a bag of soda crystals and a lot of patience! Good luck.

Alison, January 2005
I have the same problem, and it is a common problem. I have tried using a special flushing agent with no success. The cost of a new matrix is £60.00 from Europarts. I have been quoted £250.00 labour from a garage to do it. I have changed a matrix before on a Golf so I might do it myself (if the dash does not need to be removed). There is no way to flush it out as the stuff thats in there has baked solid.

Dominic, November 2004
link Click here to see other fixes for Renault Laguna.