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dumb-ass thermostat problem.

arse_sidewards

arse_sidewards

Contrary to everything
Joined
May 19, 2020
Member Number
71
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7,813
Vehicle in question is the Aerostar. The cooling system is literally identical to a 3.0 Ranger, standard V engine with coolant ports in the manifold at the front of the heads and a thermostat mounted in the manifold and temp sensor/heater core outlet below and forward of the thermostat.

Over the past couple months it was having a temp spike on warm up from cold. This would only happen after sitting several hours. Basically before work and after work.

Last week the temp spike was getting out of the "normal" range on the gauge so I figured the thermostat was opening too slowly so I swapped it out.

New thermostat does the exact same thing.

Ok, whatever, maybe there's an air bubble (I am pretty sure my intake gasket is seeping coolant into the intake on cool-down) somehow that isn't getting sucked out the heater core circuit I'll drill a tiny hole in the thermostat and see if that fixes it.

One 1/4" hole later and it won't warm up. This makes no sense since the same thermostat made it run the correct temperature after the temp spike ran its course.

Ok, maybe the new thermostat is broken because of the temp spike.

I go get a used thermostat from the parts inventory, confirm it working as it should in boiling water, drill a 3/16 hole in it, same behavior.

WTF? Should I throw another new thermostat at it? It's not like they're expensive.
 
Engine fan working properly? Any chance the spike is happening cause the fan is late to kick in before driving temp back down?
 
Toreadorranger said:
Engine fan working properly? Any chance the spike is happening cause the fan is late to kick in before driving temp back down?
Click to expand...
Yes. That also wouldn't explain why it doesn't warm up at all now. If the fan was the issue a 3/16 hole in the thermostat shouldn't have changed anything.
 
arse_sidewards said:
Yes. That also wouldn't explain why it doesn't warm up at all now. If the fan was the issue a 3/16 hole in the thermostat shouldn't have changed anything.
Click to expand...
true, I glossed over the now it doenst warm up at all bit.

Id toss in another thermostat and see if your back to just the temp spike problem. At least rule out the drilled hole as part of the current problem.

The temp spike problem started just out of the blue?
 
Toreadorranger said:
true, I glossed over the now it doenst warm up at all bit.

Id toss in another thermostat and see if your back to just the temp spike problem. At least rule out the drilled hole as part of the current problem.

The temp spike problem started just out of the blue?
Click to expand...
Temp spike problem came on slowly over the past month. It'd get to the high end of normal and then go down to the low end and then center and stay worm and act normal from there on out until I let it sit and fully cool down to ambient temp. I didn't bother addressing it until it starting spiking into an area of the gauge that made me uncomfortable because until then it wasn't a problem.
 
I would think that the intake gasket has something to do with it but there's no way that can explain the "not warming up" problem.


Does mildly overheating a thermostat result in them opening at too low of a temp afterwards? That doesn't make any sense.
 
bdkw1 said:
Clogged bypass hose.
Click to expand...
I thought that might be it but why no warm up with a tiny hole in the thermostat? Maybe I'm just destroying them overheating.

I'll try a new thremostat and looped heater hose some weeknight this week.
 
Hole letting enough water through to open the t-stat.
 
arse_sidewards said:
Vehicle in question is the Aerostar. The cooling system is literally identical to a 3.0 Ranger, standard V engine with coolant ports in the manifold at the front of the heads and a thermostat mounted in the manifold and temp sensor/heater core outlet below and forward of the thermostat.

Over the past couple months it was having a temp spike on warm up from cold. This would only happen after sitting several hours. Basically before work and after work.

Last week the temp spike was getting out of the "normal" range on the gauge so I figured the thermostat was opening too slowly so I swapped it out.

New thermostat does the exact same thing.

Ok, whatever, maybe there's an air bubble (I am pretty sure my intake gasket is seeping coolant into the intake on cool-down) somehow that isn't getting sucked out the heater core circuit I'll drill a tiny hole in the thermostat and see if that fixes it.

One 1/4" hole later and it won't warm up. This makes no sense since the same thermostat made it run the correct temperature after the temp spike ran its course.

Ok, maybe the new thermostat is broken because of the temp spike.

I go get a used thermostat from the parts inventory, confirm it working as it should in boiling water, drill a 3/16 hole in it, same behavior.

WTF? Should I throw another new thermostat at it? It's not like they're expensive.
Click to expand...
Did this on my sons nissan, 1/4" hole is too large, it needs just a pin hole, Might be too much flow to warm up.
don't know about the rest.
but the Nissan was brutal about air bubbles, It actually had a bleed screw, but a pin hole in the thermostat solved it.
Toyotas have the Jiggle valve serves the same purpose.
 
I would put a block tester on it and check for combustion gasses in the cooling system. 1/8" hole or none at all on the thermostat, they get fucky with anything more than that.
 
I'm gonna try a new thermostat with a 1/8 hole and looped heater core hoses some weeknight this week.

SLOWPOKE693 said:
You are pushing exhaust gas past the headgasket and into the cooling system.... you are not mixing coolant and oil.
Click to expand...
Yes, and I'm free of weird coolant pressurization, nasty coolant and all the other side effects of a blown HG.

This isn't my first rodeo. 99x/100 a blown HG on a 3.0 will dump coolant into oil before there are any other symptoms. I'm pretty sure it's not the head gasket.
 
Why would you put a hole in it? The cooling system has worked all it's life without one and suddenly the proper fix to your problem is adding a hole to the thermostat? :lmao:

Read my above statement slowly so it sinks in...
 
Did you check to make sure the coolant is circulating? What do the upper and lower hoses feel like once it warms up? Have you confirmed that the fins on the water pump impeller are not rotted off?
 
Looping the heater hose is a bad idea, that just let's hot water do laps through the engine without ever seeing the radiator.
 
SLOWPOKE693 said:
Why would you put a hole in it? The cooling system has worked all it's life without one and suddenly the proper fix to your problem is adding a hole to the thermostat? :lmao:

Read my above statement slowly so it sinks in...
Click to expand...
:shaking:

Jesus fucking christ you are dumb.

I own four Subarus. I think I know what the symptoms of combustion gasses leaking into the coolant look like.

I drilled a hole in the thermostat because temp spiking, regardless of source, indicates air pockets and/or poor initial circulation, both of which are mitigated by drilling a hole in the thermostat.

bdkw1 said:
Looping the heater hose is a bad idea, that just let's hot water do laps through the engine without ever seeing the radiator.
Click to expand...
You mean like it does every time you warm the engine up without blasting air over the heater core?
 
arse_sidewards said:
:shaking:

Jesus fucking christ you are dumb.

I own four Subarus. I think I know what the symptoms of combustion gasses leaking into the coolant look like.

I drilled a hole in the thermostat because temp spiking, regardless of source, indicates air pockets and/or poor initial circulation, both of which are mitigated by drilling a hole in the thermostat.


You mean like it does every time you warm the engine up without blasting air over the heater core?
Click to expand...

You own 4 Suburaus and an Aerostar yet I'm the dumb one... :lmao:


You have this figured out, why post a thread about it if drilling a hole in the thermostat is the end all be all magical fix to the issue? Put the fuckung thermostat in straight out of the package, without drilling a fucking hole in it, and figure out the real fucking problem.
 
SLOWPOKE693 said:
Put the fuckung thermostat in straight out of the package, without drilling a fucking hole in it, and figure out the real fucking problem.
Click to expand...
I did that. Same temp spike so I figured out exactly nothing. So I'll try looping the lines with a new thermostat tomorrow.

SLOWPOKE693 said:
You own 4 Suburaus and an Aerostar yet I'm the dumb one... :lmao:
Click to expand...
Says the dumbass that plays with SxSs. Such a shame you haven't died crashing one yet.
 
arse_sidewards said:
Says the dumbass that plays with SxSs. Such a shame you haven't died crashing one yet.
Click to expand...
Dude what the hell is wrong with you?

Don't fucking wish death on someone over trying to help you on the internet, you can fuck the right off with that shit.

Life is fucking short asshole
 
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