L400 heater core repair/removal

thelazygreenfox
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Joined: Tue Jun 08, 2010 7:21 am
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Vehicle: 99 white Hi roof gas Chamonix
Location: Coquitlam B.C.
Location: coquitlam canada

L400 heater core repair/removal

Postby thelazygreenfox » Sun Dec 15, 2013 2:17 pm

1.-If it was plugged then backflush the heater core from under the hood in case it can be fixed w/o dismantling the dash. Remove the heater hoses and backflush the core several times. Try pickling with phosphoric acid or bleach and low pressure water flow. If the backflush water cleans up reconnect the hoses, refill the coolant, bleed the air out and turn on the heat. Happy? Have a beer!

2.-If not take the battery terminals off and remove your front seats. The whole job is easier and there's room to store all the bits and pieces onboard.

3.-With a flat screwdriver pop off the back of the 3 instrument pod, this will give you access to the screws that hold the pod on as well as the ones that hold the top part of the centre console on.

4.-Pop open the drinks tray holder, either side are gold screws, take these out and the drinks tray and the centre console/clock should come out. Disconnect the wiring after removal.

5.- Remove your cd player and ash tray along with the wiring behind.

The heater control unit is HCU and the air box/ heater core is AB.

6.- Remove your glove box. This gives access to the HCU push/pull cable connectors and one of the nuts on the AB. (Undo the other 3 nuts holding the AB to the firewall after you remove the dash top side vent connectors and lift the dash for easier access.)

7.-.pop the front HCU cable out of it’s AB retainer on the AB and remove the round end from the post. The rear cable clip is held on the white AB and needs pried up and off. Lift off the rear cable connector round end (near the firewall) and remove the black HCU.

8.-Remove the front plastic dash covers as needed for access to components behind it. Pop those little vents that demist the small side windows, they do take a fair bit of force to get off, undo the screws that hold on the side vent duct and pull them out.

9.- On the dash right side side remove the black ECU screws, then the bolts that retain it to the bracket. Let it hang. Remove the white duct section on the left side of the AB. The AB will not come out without these two removed.

10.-Time to get under the hood. There’s 4 pointed bolts on the upper firewall holding the whole dash in. They may need to be removed to lift the dash up.
Lower the inlet air vent and remove intercooler parts as needed then remove the 4 nuts on the upper firewall.



11.- Your dash speakers may need to be removed.

12.-With all that done the dash should lift. Gently lift the dash and brace it as high as possible woithout breaking anything. Pull up the large wiring cable above the round metal tube section. If the dash won’t lift easily more parts may need to be removed.

13.-Remove the last 3 bolts and the AB from under the dash and undo the heater core screws on the top of the AB. Repair or replace the heater core as needed and replace everything in the reverse order.

14.-Refill the cooling system with antifreeze/water, bleed the air at the vent under the hood and test drive. Check for leaks at this point. Have a beer and pat yourself on the back.

15.- Ocassionally check for leaks as clamps tend to loosen up after the job is completed.

This is just a guideline. Your application may be different and need more parts removed to repair/replace the heater core.

Some of these pics show the entire dash removed. They are just to show perspective and not to imply the dash need be removed.
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