I recently picked up a 1997 LS400 and have been putting it back together for my son. Last week we had our first snow fall and he had no heat and no way to defrost the wind shield.
After checking everything out I decided to back flush the heater core and the results were astonishing. So since the principle and items needed are the same for our trucks and other cars I thought I'd post up what I bought and how I did it.
The general idea is to plumb a garden hose in the reverse direction and run water through it from the house.
Attached is a scan of the three pieces I bought from Home depot to transition from the garden hose to our 5/8" heater hose and then from our heater hose to a 5/8" clear tubing.
The Garden hose would plumb into the return line of the system where the hose meets the hard line that runs over the top of the exhaust manifolds. The clear line would plumb into the supply side after the heater valve.
Initially I turned on the water supply slowly and gradually turned it open watching how the water ran out the clear hose to try and gauge how restricted the core was. I did see several large flakes of material and once the water was clear I fist bumped the housing and my son said clouds of stuff was flowing out at that point. Once the water flowed clear even while bumping the housing I turned off the water.
Now you can remove the garden hose and place a funnel in the hose and add anti freeze back in until you see that running out of the clear hose. Now you can put everything back together and test the system for leaks and heat output.
On our trucks you can flush the front and rear cores interdependently by clamping off one of the hoses at a time at the garden hose end.
Whole process was less than half an hour.
Sorry for no setup picks but I was doing this on a LS400. Maybe someone can post up picks should they try this and possibly post before and after vent temp readings.
From this experience I think the major issue was the flakes that I saw being flushed out and not some clog that might resemble something you would find in a drain. Our cores like most of them are divided in half so the coolant flows down one side and and then double backs on the other side leaving both inlet and outlet on the same end next to each other. So the core cross section at the inlet is probably about 2" square and a few large pieces of debris can really reduce the coolant flow which would impact how soon the heat comes on as well as it's overall temperature.
After checking everything out I decided to back flush the heater core and the results were astonishing. So since the principle and items needed are the same for our trucks and other cars I thought I'd post up what I bought and how I did it.
The general idea is to plumb a garden hose in the reverse direction and run water through it from the house.
Attached is a scan of the three pieces I bought from Home depot to transition from the garden hose to our 5/8" heater hose and then from our heater hose to a 5/8" clear tubing.
The Garden hose would plumb into the return line of the system where the hose meets the hard line that runs over the top of the exhaust manifolds. The clear line would plumb into the supply side after the heater valve.
Initially I turned on the water supply slowly and gradually turned it open watching how the water ran out the clear hose to try and gauge how restricted the core was. I did see several large flakes of material and once the water was clear I fist bumped the housing and my son said clouds of stuff was flowing out at that point. Once the water flowed clear even while bumping the housing I turned off the water.
Now you can remove the garden hose and place a funnel in the hose and add anti freeze back in until you see that running out of the clear hose. Now you can put everything back together and test the system for leaks and heat output.
On our trucks you can flush the front and rear cores interdependently by clamping off one of the hoses at a time at the garden hose end.
Whole process was less than half an hour.
Sorry for no setup picks but I was doing this on a LS400. Maybe someone can post up picks should they try this and possibly post before and after vent temp readings.
From this experience I think the major issue was the flakes that I saw being flushed out and not some clog that might resemble something you would find in a drain. Our cores like most of them are divided in half so the coolant flows down one side and and then double backs on the other side leaving both inlet and outlet on the same end next to each other. So the core cross section at the inlet is probably about 2" square and a few large pieces of debris can really reduce the coolant flow which would impact how soon the heat comes on as well as it's overall temperature.
