Spark Plugs in Heater Hoses ! Strange but true!

Jayramble

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Supporting Member
Joined
Apr 3, 2021
Messages
42
Location
Dubai, UAE
My head is still spinning as I was investigating how bad my heater was blocked as no heat was coming from the unit when turned on and when feeling the heater hoses at the water pump / engine end they were hot but not at the heater core connection - I assumed that the heater core was blocked and considered removing the whole dash to replace. Yes the actuator works - as I pulled it apart and fixed - another story!

Then following others advice I removed the heater hoses to check the back pressure - but last time I removed the hoses at the water pump end as it was easier I thought and had no flow. No flow until tonight (my time, now it si 02:46 am as I had to finish) when I removed both heater hoses (at the firewall/heater core end) and discovered to my shock that each hose was plugged shut with a spark plug! Explains the lack of flow and I can't make this up.

We tested the heater core by pushing water in both directions and no obvious leaks in the cabin - we checked under each side and pulled back the carpet for some time and will check again in the morning.

Upon reflection I assume a previous owner did this to stop the transfer of heat into the cabin and make the AC work easier - Dubai summers get to 50 degrees C (122 F). And I discovered other oddities over the past two years including all HVAC vacuum actuators wired closed except the face vents - not sure why!

In a range of old Jeeps (TJs and XJs), I have seen the heater bypassed when the heater cores fail but that is usually just looping the heater hoses connections at the water pump.

Has anyone heard of a similar blockages in heater hoses?

Feedback welcome...
 
  • Wow
Reactions: MikeE024
Not very smart of them since the heater core is where coolant flows until the thermostat opens. If they knew what they were doing they would have just bypassed it.

I think you're probably right. It's pretty common for these things to blow a little warm air to the floor vents even when AC is on, so maybe they were trying to eliminate every bit that they could.