Heater Problem

[Javi_dsm]

Hey guys I need some veteran help, because I'm so confused.

So I have a 1998 eclipse gs with a 420a motor (first car/dsm), and quite frankly I don't understand the heater system.

When I bought the car it had it's issues and slowly I've been fixing every major issue. But one thing I don't and about to give up on is my heater.

When I first got it, it only blew cold air. So then on I have replaced Hoses, Radiator, flushed the system (twice), thermostat (on my third one currently), water pump and at last I finally got minimal heat.

The catch is, the car seems as if it is going to overheat by spiking up (reading from the gauge) but cools down. And every thermostat (I started using fail safe) I have put in has blow. I put one in yesterday, come one day later and it's already blown.

Im so confused on why my thermostat keeps blowing and preventing me from having a consist heater.

 

[briansmith]

Do not use fail safe t stats. They hang open what happens is the block is steel. When the car is at op temp and u turn it off the water pump stops. The steel holds so much heat that the water temp in the block actually increases from lack of circulation. These opens the t stat fully and locks it. Now the stat is stuck open and u can't get heat because of the constant circulation. Found this out the hard way on a old 350 small block. Use a standard tstat and let us kno how it turns out. Also when bleeding the system start the car with heat on max and bleed. If not some cars have a hot water valve. This traps air in the heater core. The valve must be open to bleed air from the system fully. Hope this helps

 

[DSM1G90]

420A motors have the dreaded vertical mount T-stat, in which this major design flaw started with the 2.2L of the "K-Car" era for Chrysler that began way back in 1981.

What happens with a vertical mounted T-stat is that the coolant level is below the T-stat and when the coolant gets hot, it creates "air-lock" - high air pressure behind the T-stat to prevent coolant from rising to meet the back side of the T-stat and causing the coolant to over heat.

And, when the hot air created by coolant heat gets hot enough to open up the T-stat is when the system temps goes to normal, but meanwhile, your system is in the danger zone of overheating.

A trick that I learned during the "K-car" era was to take the T-stat, and drill a very small .050" hole in the T-stat flange and have the hole at the 12:00 position on install. This hole prevents the "air-lock" to happen behind the T-stat and never have any more issues. Plus, this hole aids in the 'burping' of the system.

I've done this trick many times, even with horizontal mounted T-stats that didn't have the jiggle valve..

I've done this trick even to my Ply turbo - NEVER have any overheating issues...and I use the factory 195 degree T-stat.

Never, never have any problems of cooling after doing this small mod.

-DSM