Overheating

Randy Baeth

Registered
I have a 4.6L DOHC out of a 94 MK VIII installed in my 66 Mustang. I'm using the Lincoln radiator (new) and electric fan- new motor. Also has a new water pump The engine has aprox 60,000 miles. It's always run around 210 degrees and I'd like to cool it a bit. I installed a 180 thermostat along with a new temp sensor. Now it runs up to 220-230 on top but only around 170 at the hoses coming out of the thermostat housing, The radiator stays cool.
It's at a shop now and we're all scratching our heads looking for the problem.

Thoughts ??
 

billcu

Head Moderator
Staff member
I thought there was a problem with using some aftermarket thermostats. Something about they restricted the flow more than the original thermostat.
 

Randy Baeth

Registered
It's hard to find a decent brand anymore. O'Reilly's, Autozone, ect. Everything comes from overseas. We're going to drill a hole in the new one (after checking to see if it actually opens at the stated temp.
Your Lincolns are beautiful. My engine came out of a wrecked 94'
 

Randy Baeth

Registered
Thank you ! We ended up taking the guts out of the new 180 and that helped a lot. Runs up to 200 or so and then the fan kicks on and back down to 185. Took the car to Goodguys yesterday and it ran fine. If I could figure out how to add a picture - you could see how the engine looks in a 66 Mustang
 

driller

El Presidente
Staff member
As an FYI...

The Mark VIII incorporates a coolant bypass system which basically circulates coolant via the bypass hose from the coolant crossover to the thermostat housing when the t-stat is closed which prevents flow from the radiator. This allows coolant flow through the engine during engine warmup.

As the engine coolant warms up, the thermostat opens and allows flow from the radiator but also simultaneously closes the bypass circuit. An improper t-stat does not properly block the bypass when the t-stat opens creating a "short circuit" of coolant that does not pass through the radiator. Since the coolant flow through the radiator is compromised from the flow via the bypass, the operating temperatures will be higher than desired.

cooling.jpg
 

Randy Baeth

Registered
Ok, one of the issues I have is that while the engine is out of the MK VIII, it's in a 66 Mustang. And we plumbed it differently. My radiator cap is in the hose between #9 & #10, and my overflow tank ia also on the left with the hose coming off the radiator cap connector. I cannot figure out how to attach photos but if you could provide your email - I could send pictures of how mine is set up. Most of the initial build was over 10 years ago so I'm a bit fuzzy on the details. The shop took the guts out of the thermostat I bought and it seems to be working ok. Runs up to 190-200 and when the fan comes on, drops back to 180-185. Only driven maybe 25 miles but much better although the temp fluctuates all the time.
 

driller

El Presidente
Staff member
Randy, I send my email address on your profile. Click on your avatar and go to your profile posts. ;)
 

driller

El Presidente
Staff member
Randy sent me pics of his setup to post...

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20220726_163158_resized.jpg

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The following is a copy/paste of my reply...

"I’ve seen similar setups in engine swaps with the radiator fill cap inline like you have it. I’ve also seen inline t-stat housings with and without a fill cap function fine where you have your fill cap. Those that use the inline t-stat/fill cap simply do away with the oem t-stat housing and have the lower radiator hose direct to the oil filter adapter housing with a small branch off it to the coolant reservoir. Then they either block off the bypass line at the coolant crossover or do away with the coolant crossover and use AN lines to a Y fitting at the inline t-stat housing.

Regardless, the same holds true as I described with using the bypass type t-stat housing. When the t-stat opens to allow flow from the radiator, it closes the bypass hose inlet from the crossover pipe. That’s why the t-stat has that large disc on the end of it. When the t-stat is closed (cold) - the disc is away from the bypass opening and coolant flows through the t-stat housing from the bypass hose from the coolant crossover to the engine through the oil filter adapter housing. When the t-stat opens (hot) - the disc moves to choke off the bypass opening blocking flow from the coolant crossover which of course now means coolant flows through the radiator then through the t-stat housing to the engine.

Think of it as a temperature operated 3-way valve. If the bypass is not closed when the t-stat is fully open you have a short circuit of coolant flow from the crossover pipe through the t-stat housing along with the flow from the radiator. This takes away from the radiator flow and hence the higher operating temps.

From what I see when you get the proper t-stat you should be fine. "

Hopefully the Reische thermostat will allieviate the symptoms. :)
 

driller

El Presidente
Staff member
I searched forever for this pic...

untitled.jpg

What I wanted to point out was the orientation of the thermostat and the arrangement of the O-ring seal in relation to the thermostat and housing. If you remove the entire assembly by disconnecting the hoses, replacing the thermostat is easy.

You can do it leaving all or most of the hoses connected but it becomes a PITA getting the thermostat and O-ring installed while bolting the housing back together.

It appears to me you have a LOT more room for freedom of movement around the thermostat housing in the Mustang engine bay, so it may not be such a challenge. ;)
 
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