autox19

so I posted this issue in a different forum. as different forums have different people, minds, thoughts etc, I thought I would post this here. This is what I have. a JDM B16a in a Fiat X1/9 (mid engine) I had big issues with it over heating from day 1. Wanted to make sure it is known it was never cooling properly before so i cant go with the "what changed" scenario. What happens. it runs up to 213 or so before I chicken out and shut it down. when I do this, the radiator is cold. what I have done. Head gasket, water pump, stant super stat thermostat. what I currently have is in this diagram. (heater has been bypassed, might come later, but right now it is not in the equation. )


Odie

DumpdEJ6

You need the thermostat to be on the hot side, from what I can see, it's on the cold side. If it's on the cold side of the radiator, it won't open up, allowing the hot coolant to flow through the radiator. The thermostat is designed to open up and allow coolant to flow through the radiator, but from your diagram it looks as if it's located AFTER the radiator, so hot coolant is never actually getting to it. You need it to be on the hot side, between the engine and the radiator.

autox19

From the looks of the water pump, the thermostat goes to a return tube to that goes to the center of the waterpump then to the engine. I thought the coolant runs from the engine/head, to the radiator and back to the return going to the water pump. I havent seen a system that goes from the pump, to the radiator then back to the engine.

Odie

autox19

looking at the thermostat housing, it looks like the return from either the bypass (form the intake) or the heater circuit dumps straight on the hot side of the thermostat. (where the wax plug is)

Odie

DumpdEJ6

It's possible it gets some hot coolant from the bypass, but obviously it's not enough for it to open. The thermostat should get coolant directly from the engine, then allow it to flow through to the radiator, and then into the water pump, which continues to circulate it.

autox19

So how do I go about reversing it? I can't move the thermostat because it is where Honda put it. I can't reverse the flow of coolant because it is how Honda built it. Looking at images on Google, the hose from the bottom of the radiator goes to the back of the thermostat.

Odie

DumpdEJ6

I think your diagram may be off somewhat then, I thought you had a relocated thermostat or something. It's possible that I don't have the correct flow path in mind. If it's as honda designed it, then I'm hard-pressed to find any issues with it and with everything you've replaced...

autox19

It was a quick in Visio. Basically. Goes from head to top of radiator, from bottom of radiator to thermostat to water pump. Heater out of head (smaller tube) to top of expansion tank. From bottom of expansion tank to right behind the thermostat (stock heater return). And the bypass that comes from intake to behind the heater return

thanks for your help!

odie

autox19

although, it did get me thinking, I have seen some diagrams that have the heater dumping onto the thermostat and some that have the bypass. I have the heater. I am now thinking it should be the bypass as it would have no way of artificially cooling down from the heater core. Even though I dont have the heater hooked up, it is possible my stainless expansion tank is lowering the temp enough that is wont fully open the thermostat.


Odie

JRCivic1

I would try looping the heater in/out and take the expansion tank out of the equation for the time being... and swap the thermostat with a genuine Honda one and try again. If it still gets hot then, you have one of two issues: The radiator itself is not getting enough air through it or the engine is damaged. Make sure the intake/cylinder head bypass hose is on the correct port of the thermostat housing... you want that circuit to close when the thermostat opens up.

autox19

Thanks for the info! I will swap the heater return and the bypass so the bypass is closer to the thermostat. Also will order a honda thermostat. would make sense if part of the thermostats job is to close off the bypass that I am not getting enough pressure through the main (radiator) circuit. and even though Stant makes good products, it might not be set up to close off the bypass correctly. right now Flow is my biggest issue. the radiator stays cold even with I am above 205. it is a new system, from the hoses, to the pipes along the bottom to the radiator itself is new. Purging air is also not fun, as it is tricky even with the stock fiat engine. Between the 2 purge valves I think I am set on that though.

Will let you know once the thermostat comes in.

Odie

Black R

autox19

I have the bypass circuit circuit, so I am good on that. good to know I am not the only one that looked at a wrong diagram! ordered the thermostat. from googling it looks like part Honda 19301-PAA-306 for a 1994 del sol vtec will work.

Odie.

autox19

Thank you all!!! I have cooling!!!! ok, it was only in the garage as i have a few other things to do before I can drive it down the road. but... I replaced the thermo with a oem honda, I swapped the heater return with the bypass. and once it hit 190, it bounced between 192 and 186 with the radiator warm!!! I do have to do another coolant purge, as I have a leak at the thermostat. obla di obla da. Also posting an idle issue in another thread.

Odie

TheShodan

iTrader: (14)

Nice solution! If you can show photos of what you did on the heater bypass, or if, that would be helpful to the community ( you can even upload them directly here without the need of a third party link.) I can make this a "sticky" as part of a new section for Bseries-swapped minis. It's becoming much more common now.