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Radiator replacement questions

2650 Views 16 Replies 9 Participants Last post by  Mike Diaz
1. i just got a CSF radiator off radiatorexpress. the plastic crap.. the install fits and all. but the old Cap doesn't fit the new radiator.. so i got one from autozone,the new cap fits but really tie, i have to force it.. should i keep that cap or order one that from CSF??.. the old cap has a spring in it. and the new one doesn't.. hope you guys understand my discription.. with or without the spring in the cap, can i still use it?

2. After i install the new radiator and everything back together. i want to use water to flush out the old coolens inside the system.. after 10minuts with the heat on Max.. the top hose is hot but the bottom hose is cold.. does that mean the thermastat needs replacement??.. but how can it go bad??.. it was working fine before(2 days ago).. i left the car over night with the bottom hose open.. can the thermastat go bad by just leaving the hose open out? without water(like a fish)?

3. i took off the Thermosensor.. and there's a small little black rubber(O-ring).. it broke.. where can i find that part??.. or do i need it??
thanks for reading my newbie questions..
1 - 17 of 17 Posts
i believe the top hose should be hot when the thermostat is working correctly
Autozone should have the sensor you need.

I would not take any chances w/ the thermo, replace it. My car takes almost 3 miles of driving to start to show an temp rise. Around 10 minutes the gauge will read normal temp. This condition only exists on cold mornings in my 250k coupe (yes it has a new HONDA thermostat). My sedan gets to operating temp rather quickly, but that engine only has around 50k.

I ran into the same situation with an aftermarket radiator. I had to use a nissan type radiator cap. It fit perfectly, just make sure you get the right pressure the cap was calibrated for.
Grant said:
i believe the top hose should be hot when the thermostat is working correctly
But the bottom Hose isn't HOT(same time as the upper hose).... so does that mean the thermostat is working correctly???...
That's wierd that your radiator didn't come with a cap, my CSF rad came with one.
ALnut said:
But the bottom Hose isn't HOT(same time as the upper hose).... so does that mean the thermostat is working correctly???...
I'm fairly sure the bottom hose should not be hot when the thermostat is working correctly-but I might be wrong.

Mike Diaz would be the one to answer this one definitively.
It shouldn't be nearly as hot as the top one. The bottom hose is cooler fluid going back into the engine. My all metal CSF worked/works fine with the stock radiator cap.
ALnut said:
1. i just got a CSF radiator off radiatorexpress. the plastic crap.. the install fits and all. but the old Cap doesn't fit the new radiator.. so i got one from autozone,the new cap fits but really tie, i have to force it.. should i keep that cap or order one that from CSF??.. the old cap has a spring in it. and the new one doesn't.. hope you guys understand my discription.. with or without the spring in the cap, can i still use it?
I bought a CSF all metal radiator and the OEM radiator cap did not fit either! Mine was metal top so I used a hammer and reformed the top of the radiator. Now it fits very snug.
I suspect a manufacturing defect.
Ballistic said:
I bought a CSF all metal radiator and the OEM radiator cap did not fit either! Mine was metal top so I used a hammer and reformed the top of the radiator. Now it fits very snug.
I suspect a manufacturing defect.
I've got one also. Can't use the OEM cap, but get a Nissan style cap (they are a different size) w/ the correct pressure rating and it will fit perfectly.
Dethred said:
It shouldn't be nearly as hot as the top one. The bottom hose is cooler fluid going back into the engine. My all metal CSF worked/works fine with the stock radiator cap.
but the problem is.. the bottom hose is NOT even warm or anything.. should i just leave it running for a longer time??.. like 30minuts??

i try taking the thermostat out for testing today. but it was such a pain in the ass. anyone else can give me another test of the thermostat without taking it out?? should i just drive to see if the heat needle jumps anywhere over half?? or could i get a BHG with a bad thermostat???

one more question.. i went to Honda to get a thermostat.. but the dud can't find it.. he said the numbers are different and crap.. can anyone give me the part number???. so that i can get it from HONDA..
Ballistic said:
I bought a CSF all metal radiator and the OEM radiator cap did not fit either! Mine was metal top so I used a hammer and reformed the top of the radiator. Now it fits very snug.
I suspect a manufacturing defect.
i got the CSF that's plastic on the top.. for 120bucks.. free shipping.. that wasn't worth it.. how much did you pay for your all metal??
ALnut said:
but the problem is.. the bottom hose is NOT even warm or anything.. should i just leave it running for a longer time??.. like 30minuts??

QUOTE]

whats happening is the coolant in the engine heats up. then the thermostat opens up allowing the hot coolant out of the engine to the radiator (top hose). hence the top hose is hot while the bottom one is cool. as the cooler coolant enters the engine the thermostat closes until it exceeds the thermostat rating and then it opens up again and lets that coolant out. this happens several times until all of the coolant is the same temp. when all of the coolant is the same temp (195 degrees i think).. then the coolant temp. is regulated by the thermostat and the fan
robbanks111 said:
ALnut said:
but the problem is.. the bottom hose is NOT even warm or anything.. should i just leave it running for a longer time??.. like 30minuts??

QUOTE]

whats happening is the coolant in the engine heats up. then the thermostat opens up allowing the hot coolant out of the engine to the radiator (top hose). hence the top hose is hot while the bottom one is cool. as the cooler coolant enters the engine the thermostat closes until it exceeds the thermostat rating and then it opens up again and lets that coolant out. this happens several times until all of the coolant is the same temp. when all of the coolant is the same temp (195 degrees i think).. then the coolant temp. is regulated by the thermostat and the fan
thanks for the explaination..
1). if the thermostat is bad.. and i drive it.. can i totally damage the car(like BHG)??

2). if i am to take out the thermostat.. can it be done without taking the throttle body, because the throttle cables are in the way..
and when putting it back in.. should RTV be used? and what's the part Number for a new thermastat if i am to buy it from Honda?. the HOnda guy told me he can't find it ... i got a 91 LS 4door.

thanks for all your help so far .. :bowdown:
ALnut said:
thanks for the explaination..
1). if the thermostat is bad.. and i drive it.. can i totally damage the car(like BHG)??

2). if i am to take out the thermostat.. can it be done without taking the throttle body, because the throttle cables are in the way..
and when putting it back in.. should RTV be used? and what's the part Number for a new thermastat if i am to buy it from Honda?. the HOnda guy told me he can't find it ... i got a 91 LS 4door.

thanks for all your help so far .. :bowdown:
1) your thermostat is probably not bad it is just recomended to change when you do your radiator. I'm sure there is a DIY somewhere.

after doing any work on your car you should always check for leaks and such. just drive it around the block a few times watching the temperature guage closly. then when you get home check for leaks.

2) I believe that the thermostat has a rubber gasket around it. so I would not recommend taking it off the stat, not sure how effective the seal would be since they are incorporated into each other.
No i don't think you need RTV and buy the stat from a Acura/Honda dealer.
ALnut said:
1. i just got a CSF radiator off radiatorexpress. the plastic crap.. the install fits and all. but the old Cap doesn't fit the new radiator.. so i got one from autozone,the new cap fits but really tie, i have to force it.. should i keep that cap or order one that from CSF??.. the old cap has a spring in it. and the new one doesn't.. hope you guys understand my discription.. with or without the spring in the cap, can i still use it?

2. After i install the new radiator and everything back together. i want to use water to flush out the old coolens inside the system.. after 10minuts with the heat on Max.. the top hose is hot but the bottom hose is cold.. does that mean the thermastat needs replacement??.. but how can it go bad??.. it was working fine before(2 days ago).. i left the car over night with the bottom hose open.. can the thermastat go bad by just leaving the hose open out? without water(like a fish)?

3. i took off the Thermosensor.. and there's a small little black rubber(O-ring).. it broke.. where can i find that part??.. or do i need it??
thanks for reading my newbie questions..
1. I had one of those radiators on my 91 Sedan. I replaced it twice (lifetime warranty) because of the poor quality. I had to take a piece of sandpaper and take off a small layer of plastic from around the radiator cap mount. Just sand it until your cap fits. The mold must have been a little too big when they manufactured the radiator.

2. If you bought a thermostat from AutoZone, and it's not working, it doesn't surprise me. I can't count on two hands that amount of bad thermostats I've bought from A-Z and other parts stores. OEM is the way to go. What you need to do is drive your car for about 10-15 minutes, and then carefully check your lower radiator hose to see if it's hot or cold. You should also check your heater hoses at the back of the engine and make sure coolant is cycling through there too. If all the hoses are hot, you're probably ok. If one of the heater hoses are cold, then you may have a clogged heater core (not a common problem). If the lower radiator hose is cold after your drive, I would venture to say that you either have a thermostat or water pump problem.

3. go to the dealer, it'll only be a few bucks.
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Mike Diaz said:
1. I had one of those radiators on my 91 Sedan. I replaced it twice (lifetime warranty) because of the poor quality. I had to take a piece of sandpaper and take off a small layer of plastic from around the radiator cap mount. Just sand it until your cap fits. The mold must have been a little too big when they manufactured the radiator.

2. If you bought a thermostat from AutoZone, and it's not working, it doesn't surprise me. I can't count on two hands that amount of bad thermostats I've bought from A-Z and other parts stores. OEM is the way to go. What you need to do is drive your car for about 10-15 minutes, and then carefully check your lower radiator hose to see if it's hot or cold. You should also check your heater hoses at the back of the engine and make sure coolant is cycling through there too. If all the hoses are hot, you're probably ok. If one of the heater hoses are cold, then you may have a clogged heater core (not a common problem). If the lower radiator hose is cold after your drive, I would venture to say that you either have a thermostat or water pump problem.

3. go to the dealer, it'll only be a few bucks.
i have this Warranty form to fill out.. did you install it yourself??. did you bring it to the shop to get all these Pressure test???.. and had to put in those PSI numbers...

For anyone buying a NEW radiator.. NEVER go with the plastic crap.. it looks cheap it feels cheap and it's not worth it.. put an extra 20 -30 bucks for a better one(anything that's NOT plastic)..
ALnut said:
i have this Warranty form to fill out.. did you install it yourself??. did you bring it to the shop to get all these Pressure test???.. and had to put in those PSI numbers...

For anyone buying a NEW radiator.. NEVER go with the plastic crap.. it looks cheap it feels cheap and it's not worth it.. put an extra 20 -30 bucks for a better one(anything that's NOT plastic)..
Modine all metal is definitely the way to go.

I install everything myself. I was installing it at the same time as the head gaskets, so the pressure test wasn't needed.
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