Thermostat?

[Zac7803 24]

Looking at replacing the thermostat on an 85 720. All the replacements seem to come with no gasket. From what I have read I need the 180F. I assume it would be a good idea to replace the old gasket with a new one correct? Also is there a brand I should replace with?

[datzenmike 39,683]

Go by price. Anything $8 and up US should be alright. Do NOT get $1.99 WallMart parts. They fail, you over heat and warp head blow gasket.

 

Go to dollar store and get a hand held hole punch. Get two, one round and one with a straight edge like a diamond. Trace out the thermostat cover, use a drinking glass for the center hole or whatever fits. Buy gasket material or if like me a Cheerios box.

 

 

 

 

My thermostat housing is gasket material but the thermostat cover, oil pump and water pump are all cereal box. Been on for years.

 

Buy the hole punch and never have to drive into town for another gasket. 'Course if you are a GM owner you could just slather RTV all over it like toothpaste and then wonder why the rad is plugged.

 

Pulled this blue RTV worm out od a Datsun head.

 

 

[Zac7803 24]

Dang mike I would not have taken you as a cereal box gasket maker, I like it. The gaskets are pretty cheap I think I will splurge. So do I need the round o-ring as well as the gasket?

[datzenmike 39,683]

They are cheap but in the time to drive into town you can make one... if you are in a pinch and have the tools. Looks like the gasket lower left 27153.

 

Take a good look at the mating surface for pitting from corrosion. Sand paper on table and rub it away.

 

 

The first thing I did in auto shop was make a gasket from a paper towel. I was so disappointed. I thought we would be tearing down 426 hemis.

[Zac7803 24]

Ok sounds good thanks Mike. I really appreciate your knowledge and prompt responses!

[datzenmike 39,683]

I want you out there enjoying your truck

[KELMO 2,424]

If you have no luck with the aftermarket, send me a PM. It is possible that I have the correct gasket around here somewhere.

[banzai510(hainz) 4,895]

a part store should have a gasket

you sure its BAD?

 

Only say that as after 30 years bolts start busting then you  need a housing and then a sender and Hex nut to holt it in then turns into a night mare.

Other times its just fine. I alwasy have a bottle of antiseize and smear on the bolts to keep from rusting and on the threads for next time

[Zac7803 24]

57 minutes ago, banzai510(hainz) said:

a part store should have a gasket

you sure its BAD?

 

Only say that as after 30 years bolts start busting then you  need a housing and then a sender and Hex nut to holt it in then turns into a night mare.

Other times its just fine. I alwasy have a bottle of antiseize and smear on the bolts to keep from rusting and on the threads for next time

No I am not sure its bad. I haven't driven it a lot, mainly around the block a few times. The temp seems to stay put, but when feeling the lower radiator hose its pretty cold. My neighbor has me partially convinced it may be bad. I guess I am just trying to prevent major catastrophe down the road.

Edited February 12 by Zac7803

[MikeRL411 3,440]

18 hours ago, Zac7803 said:

Looking at replacing the thermostat on an 85 720. All the replacements seem to come with no gasket. From what I have read I need the 180F. I assume it would be a good idea to replace the old gasket with a new one correct? Also is there a brand I should replace with?

 

In my  experience after market thermostat gaskets are too narrow for Datsun products,  Gaskets for Chrystler products are wider across the mating surface and seal much better.

[banzai510(hainz) 4,895]

well what is the temp after you drive around awhile?

If its real cold then the state is open all the time. Your Heater will be cool also.

 

but if your in the normal range of the temp gauge then the state is closed and the radiator is doing its job and the lower hose should be cooler.

[datzenmike 39,683]

A 180F thermostat will warm up to (about 15 min depending on the weather) and stay at or just a thin hair above the half way point in the marked 'run range'. It might go up a needle width if climbing a long hill and it may drop a needle width rolling long enough going down a long hill. But generally about the half way position. Where does yours run?

[Zac7803 24]

I would say mine runs right there (halfway) it climbed up above half and then settled back down to half or slightly below half. But like I said this is just around the block not even getting to 3rd gear. 

[banzai510(hainz) 4,895]

I guess you got to drive it it around and give us a better description.  like a 1/2 hour. and get up to speed and then idle in traffic.

 

I can warm up 15 mins and go around the block. and be fine also in my jeep

 

But its different if you just start up on a cold day and go around the block right away and its halfway is alot different

 

 

lIke I said does the heater get warm? also

 

 

really you know this truck better than anybody has it changed temp levels abnormally from say last month or is this cause the neighbor said something.

 

Datzenmike is a Z series expert on those motors. Im just guessing

[datzenmike 39,683]

The temp sender is right below the thermostat so half way on the gauge is what I call normal 180F. This is the water coming out. If later it climbs more than a needle width higher when doing work that would be a failure of the rad to do it's job. Over heating is not always the thermostat.

 

Heat transfer from the rad can be one of two things.

 

Air flow (or lack of)

Faulty clutch fan. Loss of friction oil causing too much slippage.

Loose fan belt, fan slipping

No fan shroud.

Rad fins damaged, missing or plugged with debris and bugs.

Fog lights, bush bar, license plate or spare tire mounted if front of rad blocking air

 

Coolant flow (or lack of)

Hard water scale blocking the internal rad tubes.

Leaking heater so both heater hoses joined by-passing hot water right back into hot engine

Soft lower rad hose collapses from pump suction at high speeds.

Loose fan belt, pump not turning enough

Low coolant level.

[scooter 320]

On 2/11/2021 at 4:18 PM, datzenmike said:

Go by price. Anything $8 and up US should be alright. Do NOT get $1.99 WallMart parts. They fail, you over heat and warp head blow gasket.

 

Go to dollar store and get a hand held hole punch. Get two, one round and one with a straight edge like a diamond. Trace out the thermostat cover, use a drinking glass for the center hole or whatever fits. Buy gasket material or if like me a Cheerios box.

 

 

 

 

My thermostat housing is gasket material but the thermostat cover, oil pump and water pump are all cereal box. Been on for years.

 

Buy the hole punch and never have to drive into town for another gasket. 'Course if you are a GM owner you could just slather RTV all over it like toothpaste and then wonder why the rad is plugged.

 

Pulled this blue RTV worm out od a Datsun head.

 

 

 

 

Good idea on the hole punch, I used razor blades but this would make for neat rounded corners. 

i prefer beer boxes myself for material.. 

[datzenmike 39,683]

I don't drink, so... Used to be a pressman at Mead Packaging. Beer cases had a water resistant agent added to the varnish coating (shine) on the outside and another printable 'Aqua-shield' on the inside so the box was more resistant to wet softening. A 24 is pretty heavy, even cans. My Cheerios thermostat housing gasket has been on for years.

 

I have another punch with a diamond shape. Nips into tight corners and will cut a straight line.