Well well- back again to this problem. Heater core was the culprit
last time - replaced 2 years ago.
This modle van has the dual heater core setup.
Should i do a system clean with a prestone coolant system cleaner?
HOw should I go about removing the very possible obstruction? Reverse
flushing the system, and where would I tyr to force water through?
Would you suggest using a T-in line kit for back flushing, or would the valves for the rear heater core obstruct back flushing?
I HAVE to get this right before cold weather...my son has a tought problem
with Rheumatoid Arthritis, and he is very susceptible to cold drafts...
Your guys experience with this modle is GREATLY apppreciated....KEV

Bought prestone system cleaner with main ingredient of sodium citrate(mild alkaline). Drained radiator and added sytme cleaner. Drove vehicle for at least an hour-cold heater core. Added 2nd prestone cleaner and drove for a total
of about 6-7 more hours of several days. Heat fully returned. Flushed system with opne petcock continually running vehicle. Drained and added almost 2 gallons of anti-freeze.
This vehicle probably had never had a systme clean like this. Sodium citrate is a very mild alkaline solution, and probably neutralized acid buildup from the old anti-freeze and crud buildup in the system....working very well, but 70 farenheit outside......KEV

My intuition was working overtime when I did the long system clean, and
after the heat seemed to be working strong, the water pump started to leak. 117K miles not too bad for a water pump. A solid 3+ hours to install
it; factory water pump gasket real fun to remove with a razor blade.

I'm replacing a water pump on my 95 3800 now, Good info on the flush I wanted to flush mine first but the old WP didn't agree. Did you back-flush? Where did you access the system? I bought a flush kit but havn't opened it.....I need more info first.

I did not back flush the system. I do not like the possibility of plugging the system with the dual heater cores. Again, I used the Prestone system clean, which is a mild alkalizing
agent, and eneded up using 2 larger containers. The key is to drive the vehilce for several hours. I ws concerned about loss of lubrication for the water pump, and alas, I ended up rreplacing it. At 120K miles, due for one anyway. Better now than in early February (near Chicago).........good luck....I hope my heat works when it is cold...KEV