running cold ?

[Stupid_fast]

Been tuning in my 510 a bit and have been wondering about this for a while.

Its a cammed rebuilt L20b with 32/36 and new/5000mile fiero radiator, stock fan and an autometer short sweep temp gauge. When its warmed up, it shows about 150*, in traffic it sits right at 180*(saw 185 once on a hot day, never went over), on the freeway cruising 70mph it sits at 140-150*. But on a backroad, 3-6k rpm the temp drops way down, stays around 110-120 on the gauge. Is this normal? The oil pressure is the same as when its warmed up (30psi @ 1400rpm idle) and there is no change in how it runs, other than not wanting to idle after WOT(float setting needs work.)

 

It takes about 5-10 minute to fully warm up to where it feels good, I let it sit for about 1 minute before driving it.(so the carb will idle with that cam...)

 

Would it run better, or more efficeintly if it where warmer?

Is it normal for the water temp to dip so much?

 

The thermostat is new, I have tested 4 and they all are consistant on the stove test. they are 180* thermostats. Maybe I should get a 195* ?

[ggzilla]

180 is normal. But it depends on the thermostat.

 

Nissan sells three different thermostat the L20B:

* 170 degree for "tropical use"

* 180 degrees

* 190 degree for "cold zones" (so the heater is hotter)

 

If you get a 195 there will be no advantage. Engine oil is formulated to work best with a 180 thermostat. You could use a 195 and rejet the carburetor leaner for more fuel economy. But if you do that make sure the temp is stable and the air intake temp is stable (e.g. use factory air cleaner with heated air intake). That's what most american cars in the 1970s and 1980s did.

[I'm BLUE]

Temperature sender(s) and wires leading to them go bad or corroded over-time.

Wire in another gauge if in doubt of it.

 

4 t-stat's ? wow.

 

I haven't seen an Nissan T-stat go bad fast ... they are consistently good stuff.

[Z-train]

Get a loaner guage and confirm numbers.Something ain't right.If you car was here the guage would be saying that the cooling system was keeping the motor BELOW ambient air temp.

[datzenmike]

If ever in doubt throw the thermostat away and instal a new 180/185F one. (it's stamped into the bottom) They aren't worth the time and bother to test and are cheap (get a good $10 one) If the reading are the same you're fine. After market gauges and senders??? who knows how they are calibrated???... Borrow an IR heat gun and shoot the thermostat housing for a truer reading.

 

Big drops at speed would indicate to me that the thermostat is partly open at all times and over cools. It should restrict flow when over cool and open fully at idle and slow around town.

[Stupid_fast]

180 is normal. But it depends on the thermostat.

 

Nissan sells three different thermostat the L20B:

* 170 degree for "tropical use"

* 180 degrees

* 190 degree for "cold zones" (so the heater is hotter)

 

If you get a 195 there will be no advantage. Engine oil is formulated to work best with a 180 thermostat. You could use a 195 and rejet the carburetor leaner for more fuel economy. But if you do that make sure the temp is stable and the air intake temp is stable (e.g. use factory air cleaner with heated air intake). That's what most american cars in the 1970s and 1980s did.

Okay.

 

Temperature sender(s) and wires leading to them go bad or corroded over-time.

Wire in another gauge if in doubt of it.

 

4 t-stat's ? wow.

 

I haven't seen an Nissan T-stat go bad fast ... they are consistently good stuff.

The wires are new, I wired it myself and I'm fairly competent with wiring and electronics.

I put in the autometer gauge because the stock one does not work correctly.(always hot)

 

I thought the thermostats where bad, but they are all working exactly the same. Spares are good! lol.

 

I need to buy nissan ones, these are car-part store whatever off the shelf.

 

Get a loaner guage and confirm numbers.Something ain't right.If you car was here the guage would be saying that the cooling system was keeping the motor BELOW ambient air temp.

Okay I'll check it.

 

If ever in doubt throw the thermostat away and instal a new 180/185F one. (it's stamped into the bottom) They aren't worth the time and bother to test and are cheap (get a good $10 one) If the reading are the same you're fine. After market gauges and senders??? who knows how they are calibrated???... Borrow an IR heat gun and shoot the thermostat housing for a truer reading.

 

Big drops at speed would indicate to me that the thermostat is partly open at all times and over cools. It should restrict flow when over cool and open fully at idle and slow around town.

I tried four different ones... all the same result, and they all work consistantly on the stove.

 

I should buy nissan thermostats... Can I just go to a parts counter at a dealer to get these parts ?? Im use to ordering everything online.

 

 

 

Thanks for the replies, I will verify the temperatures and see if it really is running cool.

[ggzilla]

I think it's worth the time to check them. They are $10 or more at Nissan. Only takes a few minutes to test them and you can do it inside the house.

 

 

it shows about 150*, in traffic it sits right at 180*(saw 185 once on a hot day, never went over), on the freeway cruising 70mph it sits at 140-150*. But on a backroad, 3-6k rpm the temp drops way down, stays around 110-120 on the gauge. Is this normal?

It is fairly common.

 

Dropping to 110 is not supposed to happen as the thermostat should keep the temp up inside the engine. But there is a problem with L20B thermostat housings where the temp doesn't always read correct (even though the engine temp is correct). See http://datsun1200.com/modules/mediawiki/index.php?title=L-series_Engine_Swap#Thermostat_Housing

[I'm BLUE]

Never said you weren't competent man .. where did that come from :lol:haha ! :console: anyways..

I use autometer stuff as well , and sometimes they are a touch/bit off no matter what you do and will read like this forever.

What you're describing isn't a touch/bit.

 

Yup ,,, go to the Nissan parts slinging dealer ,,, parts counter ,,, order one up

Call them first. They will usually say if in stock and availability if not/order time.

Stant works "ok". I won't use Murry or Moto-rad. ( It's just a preference , not personal to anyone )

Nissan is good stuff.

 

I'd quad-druple check for any coolant leaks or air-pockets in the cooling system. Longer shot , but meh what else ?.

( I have no idea if worked on recently or what ? you know your car best )

 

ggzilla sounds like he;s got a good idea.

[datzenmike]

The thermostat is new, I have tested 4 and they all are consistant on the stove test. they are 180* thermostats. Maybe I should get a 195* ?

 

 

Good enough they are working. Forget what the temp gauge says.

[Laecaon]

Do you get heat out of the heater when the gauge is low?

 

I had a 165 in my car, (and a 3 row radiator), and in the winter the heater wouldnt even give anything above luke warm. As soon as I dropped in a 195, bam heat.

[datzenmike]

Jacob, he says that...

 

The thermostat is new, I have tested 4 and they all are consistant on the stove test. they are 180* thermostats. Maybe I should get a 195* ?

 

So 4 all pass the hot water temp test @180 F, so you have to assume they are working in the head. If the gauge says 110- 120 it has to be wrong.

[ggzilla]

So they pass the 180 test ... but do they pass the 120 test?

 

You have to watch the thermostat as the pot of water cools down. It should immediately start closing as it goes below 180. And be fully closed by 170. If it stays open too long your temps in the engine will drop after the radiator water cools down.

 

All that said, it's extremely unlikely all four would be bad in the same way.

[Z-train]

Awhile back i had four bad ones in a row.Three for the parts house and one from Nissan.QC on T-stats blows.

[Laecaon]

I did see that Mike, I was more or less implying, that if the heater is hot, the gauge is definitely wrong.

 

This would not be the first time I have seen an Autometer gauge work incorrectly.

 

At work I installed an Autometer EGT on a Diesel truck. Wouldnt read consistently. Warrantied the probe, and it still wouldnt give accurate readings. Then Warrantied the Gauge, and things were a lot more consistent, but still off at idle. So warrantied the Gauge again, and finally we got one that worked right.

 

 

Oh, and I think I like stant thermostats the best. Just personal good luck with them.