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1995 454 that only provides heat when idling.
I get 148 degrees out of the heat vent when idling then drops to 70 degrees when driven a few miles or with engine rev’d for a few minutes
The problem started about 5 years ago. Have put on 20,000 miles since the problem started. The engine has never overheated and the temp gage runs consistently around 210.
The engine runs like a champ – it just doesn’t heat!
Here’s what I’ve done over the past 6 years and have run out of ideas:
1.The coolant supply line comes from the back of the block - goes to the bottom connection of heater core.
2.The coolant return line is on the top connection of the heater core and connected to the top of the radiator.
3.Checked/replaced thermostat and radiator cap
4.Checked/replaced heater control valve to make sure it's working
5.Checked for correct vacuum pressure to the control valve
6.Checked the outside of heater core box to make sure it's sealed completely to fire wall.
7.Checked the blend air door in the heater control box to see that it's moving and not disconnected inside
8.Checked the nipple coming out of the engine for blockage
9.Replaced supply and return hoses
10.Checked for a possible air lock in the heater core by bleeding the return line
11.Installed clear tube in supply line – small bubbles at idle – all foam at higher RPMs
12.Coolant block tester – indicated low level of CO2 in coolant
13.Magnafluxed heads – no cracks, some warping - planned heads and replaced
14. Replaced - water pump and heater core
15.Still have small bubbles at idle and turns to foam at higher RPMs
16. Replaced hoses
17. Rechecked vacume lines
18. Replaced heater core
What in the world could this be?
* small hole in the block?
* blockage in one of the waterjackets?
* still a crack in one of the heads?
I'm running out of ideas - help |
RV and bus conversion info since 1996.
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