Nice tidbit for those with barely any heat

[neanderpaul]

NeanderPaul, oh holy one, is there anything you DON'T know about Festivas??

Lol! I haven't learned anything new in a few years. BUT, it's been 23 years for me. I have no excuse.

[dalebwilson]

Been watching my 93GL temp needle not move off the bottom for the past month along with minimal heat inside. Today I pulled the T-Stat and found out why. What's wrong with this picture?

[william]

Stuck open . Get a tstat for a 93 mazda miata there the 2 stage ones. But to be quite honest I didn't see much if any improvement over my old single.

[dalebwilson]

Stuck open . Get a tstat for a 93 mazda miata there the 2 stage ones. But to be quite honest I didn't see much if any improvement over my old single.

Exactly!

[toecar]

Here's some school on thermostats;

http://www.are.com.au/feat/techt/thermostat.htm

[toecar]

That appears to be a "Safety" thermostat.
It is designed to "lock open" at (very) high temperature.
Sensing a mechanical failure, like high temp due to head gasket failure, the thermostat will not cool down and close, creating another very high temperature condition.
These "lock" open and must be replaced in this condition.
Look for a mechanical failure causing a very high heat condition that caused this thermostat to lock open.

[toecar]

That F201-15-171A has been superseded by 8AK1-15-171-9U.

[toecar]

800px-Double_valve_automotive_thermostat.jpg
Is THIS the image of the "Two Stage" thermostat that belongs in a '93 Festiva?

[micro_trucktiva]

No this is

[ryanprins13]

So, i read this whole thread (quite amusing at times) and i have a couple questions. One person mentioned checking the valve that controls flow of coolant into*the heater core. I have a civic that has one of those so i have an idea what they look like but i have not been able to find one on the festiva. It seems as if coolant is always flowing through the heater core in the B3 correct?

Another suggestion was to check the bypass circuts. I had a look at what mine are. Looks like theres a small hose going from by the block side of the thermostat down to the metal hose going from the heater core to water pump. Is that what is meant by bypass curcit? Is it correct that when the thermostat is closed this is what the coolant flows through to complete the loop? If thats the case that could be why these cars have low heat as that is quite a small hose.*

Third question is about the idle speed control-bypass air valve. (Bolted to the transmission side of the engine on the intake manifold.) It has coolant hoses attached to it and from what i understand the coolant temperature controls the valve which lets air bypass the throttle valve when cold. So has anyone had one of these off? Is there a valve on the coolant part of it or does coolant always flow straight through? Can this or the heated throttle body get plugged and somehow reduce heat output in the heater core?

When i first bought my car it had heat, now it doesnt. Since the heat quit i have replaced the thermostat twice, water pump, rad cap and heater core. Also many flushes. None of that helped. Its not the thrmermostat because even in -40c my temp guage goes to half. Temp gun on engine confirms that. All appropriet hoses get hot. One person on here said that replacing their radiator fixed the heat issue, so i will try that, but i doubt it will work since in -35c at 100km/hr the coolant isnt going through the rad anyway. I have lots of heat coming out the vents at +30c ambient, or even +10 its plenty. From +8c to -10c ambient it goes from hot to the cold side of lukewarm. Even after all those replacements. I bought an entire heater assembly to put in in case there is something wrong with my box but the heater core it came with is all rusted up and i dont really want to risk something not going back togeather right by splitting it and putting my new heater core in. If the heater box is the only thing you guys think could be wrong would trying acid rinses on the heater core thats in it clean it out enough that i wouldnt have to remove it?

So any any helpfulness would be helpful, thanks!


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[ryanprins13]

oh, the other weird thing is that when its cold out it blows colder on the 3rd fan speed than on the second speed. its on a 1993 stock festiva

[bravekozak]

ryan, I know it's not the thermostat. People waste their money on two stage thermostats when a single stage will do just fine. You may have twenty years of dirt buidup in the fins of your heater core if you do not have an A/C evaporator to block windblown dirt, leaves & debris. Search for a thread on cabin filters.

That little bypass hose is there just in case the thermostat doesn't open when the engine reaches operating temperature.

You are correct. Coolant is always flowing through the heater core all the time. That is why I disconnected my heater core since I only use it for summer driving only.

[ryanprins13]

Thanks! Ok, i replaced the heater core with a brand new one so its not that.


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[bravekozak]

Make sure the foam seal on the main plenum baffle doesn't let any cold air in.

[bravekozak]

The only other thing I can think of is that the coolant must flow through both holes out of the cylinder head and through the intake manifold before exiting to the heater core hose. One or both of those holes could be plugged.
I noticed on the B5 gasket from Australia that it was blocked off on the first coolant port (closest to the water pump). All of the coolant was forced to exit at the farthest port.
I guess you could remove the heater hose and poke a wire through the intake manifold to the cylinder head interface and ream it out to make sure it isn't blocked.