Thermostat replacement question

The service manual shows the complete removal of the thermo cover as well as the water passage housing under the thermostat replacement heading.

In the real world, can the thermostat be replaced by simply removing the thermo cover or does the whole shebang have to come off?

Thanks...

Hugh said:

In the real world, can the thermostat be replaced by simply removing the thermo cover or does the whole shebang have to come off?

Thanks...

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Yes, you can just remove the cover. You will remove two 10mm bolts and the electrical connectors for the temp sensor on the housing cover and TPS on the throttle body, after the air filter assembly is removed of course.

Have a BIG catchpan.


HTH,
LarryB

I was waiting for you to catch this thread.

No need to disconnect the coolant hose on the thermo cover right?

Thanks Larry!

Larry Bastanza said:

Yes, you can just remove the cover. You will remove two 10mm bolts and the electrical connectors for the temp sensor on the housing cover and TPS on the throttle body, after the air filter assembly is removed of course.

Have a BIG catchpan.


HTH,
LarryB

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How much coolant will fall out? I have a pan I use for my oil changes that holds something like 15 quarts of oil. Will that work?

Meeyatch1 said:

How much coolant will fall out? I have a pan I use for my oil changes that holds something like 15 quarts of oil. Will that work?

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Not sure how much comes out with the thermostat, but the ENTIRE cooling system holds less than 16 quarts, so guess you'd be OK. I would think you could drain from the rear engine plug and be OK for the thermostat, but not sure. A gallon or less came out of the rear engine drain when I did my coolant change.

Yes, you can, just removed the thermostat housing cover and uplug the attached sensor connectors. Not to much coolant will come out but be ready to catch as much as you can. Make sure and put the t-stat in the correct way. Also, be carefulll when tightening the 10mm bolts because they can strip easily. When I purchased my NSX the lower bolt was rusted and broken so I removed the entire water passage way. Not too bad but more time consuming. If you end up removing the water passage way for any reason be sure to order the three o-rings for the passage way when going back together.

Because I just did this for the first time myself, I can now answer the above questions:

Hugh said:

I was waiting for you to catch this thread.

No need to disconnect the coolant hose on the thermo cover right?

Thanks Larry!

Click to expand...

I didn't disconnect the hoses connected to the thermo cover.

Meeyatch1 said:

How much coolant will fall out? I have a pan I use for my oil changes that holds something like 15 quarts of oil. Will that work?

Click to expand...

In total I lost about a gallon of coolant.

I definitely do not recommend this but for multiple reasons I ended up draining my coolant (very slowly) through the bleeder bolt on the thermo cover. Elsewhere it is recommended that enough coolant is drained that no more coolant comes out through this bolt. Nope: one should drain more coolant than that. Upon removing the thermo cover I spilled some coolant and when I removed the thermostat, I spilled much more than that ~ completely defeating my reasons for trying to drain through the bleeder bolt. Anyways, after I had it back together I refilled with a gallon of coolant but had to get a bit more to get up to the proper level.

I need to do mine and am thinking of lifting the rear end of the car to reduce the coolant loss. As I type this, I am coming to a gut feeling that this won't help as it is a closed system and it's not like the coolant will just flow to the front. Hmm.

It probably won't help much with the coolant tank being the highest point of the system. You might open the bleeder on the thermostat housing until nothing comes out, but you will surely spill some coolant regardless when taking the tstat cover off. If you want to minimize spillage then you can use the two drains on the front/rear engine block too but you should prepare to do a thorough system bleed afterwards.

The thermostat is going to dump coolant regardless of how you lift the car. If the coolant was replaced recently then just drain the system into a clean bucket then just put the old coolant back in when you’re done and do a full system bleed. If it’s been a few years it’s probably best to just fully drain and replace the coolant. Also change all the hoses if they haven’t already been done.

Speedmaster said:

I need to do mine and am thinking of lifting the rear end of the car to reduce the coolant loss. As I type this, I am coming to a gut feeling that this won't help as it is a closed system and it's not like the coolant will just flow to the front. Hmm.

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As the other guys said, it's going to dump a lot even if you raise the rear. Probably best to drain the whole system and refill. You're going to have to do the full bleed procedure either way.

Honcho said:

As the other guys said, it's going to dump a lot even if you raise the rear. Probably best to drain the whole system and refill. You're going to have to do the full bleed procedure either way.

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I may just tap the housing with a mallet a-la starter motor tapping. You know, to dislodge whatever is holding that spring in place (open.) And if that doesn't work, i will do the job.