[Moby]

Lots of good suggestions, thanks for all the input! The A/C makes a huge difference in engine temp and how hard my fan works, I've never been able to get it over 200 without the A/C. And on the two occassions that it did get hot the A/C was cranked and the hills were big and long. I mean more than 15 minutes of intermittent steep hills where I'm way into the throttle, often full throttle or holding it in 3rd. The 2nd time I was loaded (wife, 75lbs dog and lots of cargo). So I was working the truck pretty darn hard. The temp climb happened over time so when I said the the temp was climbing like a rocket that probably wasn't accurate - it was a steady rise over time that was not stabilizing. Again, no regular problems during the past 1.5-2 years, including 100+ degree city driving in Sacramento, just these two incidents.

I think the most interesting suggestion is the t-stat not fully opening. This is the only part of the system that wasn't replaced during the rebuild. Also suspicious is the fact that it is an aftermarket 180 degree unit. I will likely go back to a stock 193 degree t-stat and see if that makes any difference. Of course I won't have a chance to test any changes until it gets hot next summer.

[Spook50]

Originally Posted by Moby

I think the most interesting suggestion is the t-stat not fully opening. This is the only part of the system that wasn't replaced during the rebuild. Also suspicious is the fact that it is an aftermarket 180 degree unit. I will likely go back to a stock 193 degree t-stat and see if that makes any difference. Of course I won't have a chance to test any changes until it gets hot next summer.

If you're using a Stant tstat, they naturally don't have as large an opening for coolant to flow through as a stock unit. The OEM tstats are HUGE compared to the Stant ones I see on the racks at the local parts stores.

[ntsqd]

Originally Posted by Moby

The "carb fan" is there to combat vapor lock in the EFI fuel rail.

Sort of off topic, but why are you getting vapor lock with EFI?

This should not be happening. Just like coolant, fuel's boiling point also goes up with pressure. That combined with the constant cycling of fuel through the system should eliminate any possibility of vapor lock.
If you are getting vapor lock with EFI then I would say that you are leaning out in those conditions, which would drive the engine's temperature up considerably.
Is the FPR on the opposite end of the 62's fuel rail from the supply end?

If you can operate consistently and reliably at 200 I'd say that's a good thing. The OE's didn't increase the operating temps of late models because they couldn't cool them lower, they increased to operating temps because there is more efficiency to be found there. So long as things like ring gaps don't close off and stuff doesn't melt, a higher operating temp isn't a bad thing.

[Moby]

Originally Posted by ntsqd

Sort of off topic, but why are you getting vapor lock with EFI?

This should not be happening. Just like coolant, fuel's boiling point also goes up with pressure. That combined with the constant cycling of fuel through the system should eliminate any possibility of vapor lock.
If you are getting vapor lock with EFI then I would say that you are leaning out in those conditions, which would drive the engine's temperature up considerably.
Is the FPR on the opposite end of the 62's fuel rail from the supply end?

If you can operate consistently and reliably at 200 I'd say that's a good thing. The OE's didn't increase the operating temps of late models because they couldn't cool them lower, they increased to operating temps because there is more efficiency to be found there. So long as things like ring gaps don't close off and stuff doesn't melt, a higher operating temp isn't a bad thing.

Interesting. I'm not having any problems, I was just saying that vapor lock is why that fan is there. My understanding was that underhood temp increases after shutdown and heat soaks the fuel rail. I could be wrong about the reasons but my understanding is that the fan is for vapor lock.

You're right, OE's raised the operating temp. Not sure about efficiency but emissions are better at higher operating temps. In most cases OEMs did this on engines with aluminum heads, which reject heat a lot better than iron heads. That isn't ideal for best power and it is common to swap 180 degree t-stats and lower the operating temperature for cooling fans on late model performance engines (very common on the LT/LS series of engines). However my goal was to reduce my pre-rebuilt engine's mild detonation tendency by attempting to keep the head/combustion chamber somewhat cooler (fortunately I don't have any detonation post rebuild, and I run a J&S Safeguard knocksensor to make sure it stays that way).

As a side note I know that I'm not running lean, I have an Innovate LM-1 wideband O2 in the front of my dual entry/dual exit cat (so it's like putting it in an x-pipe to see exhaust from both banks of cylinders)

[ntsqd]

When under typical EFI pressures the vapor point of fuel is enough higher that it won't boil off and become a gas (vapor). On hot shut-down the FPR and the check valve in the pump will hold the rail to the injection pressure of ~40 psi. One of the tell-tale signs of either the FPR or the pump starting to fail is when you Do start to see vapor-lock like problems on a hot re-start.

When you put in a lower temp t-stat you're not really putting the engine in a better power producing temp range. What's happening is that the ECU sees that the engine is not up to it's specified temp & increases the injector dwell. Essentially you're running in a partial 'choke' mode, which puts the engine into the range of the 12:1 power A/F ratio rather than the 14.7:1 stoich that it's programmed to run at.

Later ECU's are smart enough that they realize that something is not right and mark that sensor as suspect. Once they do that, they'll bring the injector dwell back down to the baseline fuel map, so you can only fool them for so long.

A carb may need that fan, I'd be really surprised if EFI does. Might try pulling it as those fender vents should help with reducing the underhood static pressure.

[Moby]

Originally Posted by ntsqd

When under typical EFI pressures the vapor point of fuel is enough higher that it won't boil off and become a gas (vapor). On hot shut-down the FPR and the check valve in the pump will hold the rail to the injection pressure of ~40 psi. One of the tell-tale signs of either the FPR or the pump starting to fail is when you Do start to see vapor-lock like problems on a hot re-start.

When you put in a lower temp t-stat you're not really putting the engine in a better power producing temp range. What's happening is that the ECU sees that the engine is not up to it's specified temp & increases the injector dwell. Essentially you're running in a partial 'choke' mode, which puts the engine into the range of the 12:1 power A/F ratio rather than the 14.7:1 stoich that it's programmed to run at.

Later ECU's are smart enough that they realize that something is not right and mark that sensor as suspect. Once they do that, they'll bring the injector dwell back down to the baseline fuel map, so you can only fool them for so long.

A carb may need that fan, I'd be really surprised if EFI does. Might try pulling it as those fender vents should help with reducing the underhood static pressure.

We're way off topic but since we're already here...

With a 180 degree t-stat and a Contour fan with a DCC controller set up for a 180 degree t-stat my truck normally runs around 190-194 with minimal fan effort (I have the same LED that spook is running and I have a Nordskog water temp gauge plumbed into my t-stat housing opposite the stock water temp sender). At this temp my wideband O2 has me running around 14.5-14.6 A/F ratio most of the time (at cruise, city or highway, it swings between 14.3 and 14.8 which is normal for a EFI system).

I could see what you're saying if you're running an 160 t-stat but not going from a 193 (stock) to 180. Eventually, yes, the ECU will see the engine as simply not warmed up. How it reacts to that is proprietary (well, may be spec'd in ODBCII). However I haven't seen any A/F ratios that are outside of expected parameters from cruise to WOT and from idle to 3700rpms and I have no reason not to trust what my wideband O2 is telling me.

At any rate I will likely go back to a stock OEM t-stat to see if it has any impact on my 2%-of-the-time cooling issue.

[Spook50]

Originally Posted by Moby

We're way off topic but since we're already here...

With a 180 degree t-stat and a Contour fan with a DCC controller set up for a 180 degree t-stat my truck normally runs around 190-194 with minimal fan effort (I have the same LED that spook is running and I have a Nordskog water temp gauge plumbed into my t-stat housing opposite the stock water temp sender). At this temp my wideband O2 has me running around 14.5-14.6 A/F ratio most of the time (at cruise, city or highway, it swings between 14.3 and 14.8 which is normal for a EFI system).

I could see what you're saying if you're running an 160 t-stat but not going from a 193 (stock) to 180. Eventually, yes, the ECU will see the engine as simply not warmed up. How it reacts to that is proprietary (well, may be spec'd in ODBCII). However I haven't seen any A/F ratios that are outside of expected parameters from cruise to WOT and from idle to 3700rpms and I have no reason not to trust what my wideband O2 is telling me.

At any rate I will likely go back to a stock OEM t-stat to see if it has any impact on my 2%-of-the-time cooling issue.

I keep expecting your av to give me the recipe for Bush's Baked Beans...

Even though your tstat is opening at a lower temperature, I'm still leaning towards there simply not being a large enough opening for enough coolant to travel through and sufficiently carry heat away from the engine. I'd say give the OEM tstat a go and see where that gets you.

[Moby]

Originally Posted by Spook50

I keep expecting your av to give me the recipe for Bush's Baked Beans...

Even though your tstat is opening at a lower temperature, I'm still leaning towards there simply not being a large enough opening for enough coolant to travel through and sufficiently carry heat away from the engine. I'd say give the OEM tstat a go and see where that gets you.

Very interesting about the size of the Stant. I think that mine is a Beck/Arney but now that I think back I do recall that it was smaller. I thought that it was due to the lower opening temp but now I'm very suspicious as well. I'm going to call CDan this week and get an OEM back in.

My dog will not give away recipes... he will eat them first just in case they have any nutrition value. Can't be too careful when it comes to food.

[ntsqd]

Not to be argumentative, but a small t-stat opening can have a significant advantage. There is coolant system pressure, and then there is block pressure. Block pressure comes from the pump working against a restriction and is even greater than the total system pressure. The positive outcome from that is that the coolant between the pump and the restriction is under an even higher pressure, making it that much harder to boil in localized hot spots. A smaller restriction would increase the block pressure. Depending on the pump's capability that may or may not affect total system flow.

That Toyota worked out a specific restriction size for a given pump would come as no surprise. I also think that the OE t-stat is a good call.

Depending on how smart the ECU is and what the programmed temperature tolerance is, going from a 193 to a 180 could have an effect. It would not be huge, but it might be noticeable by SOP.
I had heard that long term use of the wide bands was hard on them?