7 hours ago, thewanderlustking said:

It's been a while since I have had a Toyota RV, but I currently have two 3VZE 4Runners.  Let's start off with I live in Florida.  It's hot here is an understatement and it's a humid hot that doesn't ttransfer heat as well as a dry hot (cooling system wise).  These trucks never run the slightest bit hot, EVER.  Even when I blew the hradgaskets on Thing 1, it didn't get hot...   My trucks aren't overloaded like an RV, but they aren't running light/empty either.   So lets go down the rubber hole.

 

1)  Somebody else needs to add input here as this is RV specific and I forget the direction that needs to be taken...  The heavily loaded RV's either need to be run with overdrive off, or on.  I want to say its OFF...  Especially in hills. One way adds a crazy amount of heat into the system.  It is enough of a concern I added transmission temp gauge into my old Mini Cruiser, and now monitor that in my 4Runners.  This descries the core of your issue perfectly, hills vs flats.  

OD off is the consensus from what I've seen, and my experience supports this

7 hours ago, thewanderlustking said:

2)  Sure if you are not going to get AC working, you could remove the AC condenser.  I never would, but as a mechanic with shop access, I can also reasonably fix any AC issues my trucks have.   AC removed will drop the resale value of the truck.  Broken/installed is better than removed.  The transmission cooler and AC condenser shouldn't drop the efficiency of your radiator to the point of poor efficiency.  Saying you can't blow through them though, is concerning.  If they are clogged up with dirt/debris then you do at least need to get them cleaned out to get flow through them.  

 

DO NOT remove the transmission cooler.  These really need the extra transmission cooling.  

No intention of removing the trans cooler. I'm not worried about resale value so much as being able to travel in the mountainous West.

7 hours ago, thewanderlustking said:

 

3)  You can "recycle" your AC condenser electric fan, put it on a relay/switch for extra cooling...  But look at your primary fan clutch too.  These do eventually go bad.  

No such animal on my vehicle.

7 hours ago, thewanderlustking said:

 

4)  Check head gaskets...  

Head gaskets were done according to the receipts I have.

7 hours ago, thewanderlustking said:

 

You really need to do some diagnostics.  #1 is free, figure out which way to set the O/D switch.  #2, clean blocked condenser and transmission cooler.  Air should flow easily through them.  #3 check your fan clutch.  

fan clutch seems to be working normally.

7 hours ago, thewanderlustking said:

 

#4 and further Diag will require minimal tools.  Get a blocktestor kit, watch videos on how to use it.  Simple and cheap.  The expensive/nice kits are $125.  The cheap kit is like $30=50.  You have a 3VZE, you need to own this and know how to use it.  It takes 2-3 minutes to test it.  Get yourself a laser thermometer.  Verify your engine temps.  Look at the hoses, see if the thermostat is working.  A new one, DOES NOT mean a working one...  A decent laser temp gun is under $100.  You can get it on Amazon for $30.  I use aVERY nice Snap-On laser temp gun.   It is well worth whatever I paid for it, but not for driveway now and then and I wouldn't throw it in my truck toolbag.  I have a cheap amazon laser gun in my truck that hopefully works if I ever need it...  

I just bought a Klein laser thermometer. 

7 hours ago, thewanderlustking said:

 

The IDEAL tool for diagnosing cooling systems would be a thermal camera.  The one I use, is NOT affordable.  They have some 😂that attach to phones and are WAY cheaper.   Not sure if they are in the affordable or reasonable range yet though.   

I'm going to start with a flush and fill.

I went pretty far down this fuel economy rabbit hole on my 22re.  And I have gone WAY further with my two 3VZE 4Runners.  

The 22re "should" be seeing 15, but I'm reasonably sure I could get one up to 18-21mpg.   The vintage Toyota engine management is the biggest killer on these, and on the 3VZE trucks.  But let's ignore the 22re as I no longer have one to properly abuse.  

For 2-3years now I have daily driven a 1994 4Runner and tracked the fuel mileage religiously.  The truck is well sorted out, fresher engine, new heads, etc, etc.  It has never once gotten to 11mpg.  Most of the time it has been 8-10mpg.  Without the added aerodynamic brick on top...  Recently, I got it above 10mpg.  But it hovers now just above 10.  Mind you this is will a WELL sorted out truck.  No vacuum leaks, new temp sensors...  It doesn't burn even a tiny bit of oil.  

My 1993 though, it gets a consistent 12-15mpg.  This truck is not as well sorted out as the 1994 is, but I get significantly better mileage out of it.  And I have done nothing to it to try to improve on that.  Not a single sensor replaced.  On this truck, I have not driven it nearly as much and can't vouch for it being a solid 12-15mpg.  I had missed some fuel/mileage log entries, but that's close.  

The main fuel economy culprit is its vintage fuel management, ESPECIALLY the air meter/restrictor.  I have developed a random flat stumble now and then under just the right conditions from a stop on the 1994.  At some point it looks like somebody got into the AFM and tweaked it, it has been resealed.  Common trick to get more performance is to loosen the spring slightly.  But it also drops fuel economy drastically.  Anyways, I am reasonably suspicious of the AFM and plan on digging a bit further into it shortly.  Out of curiosity, I am going to put a Wideband oxygen sensor onto the truck first and see what the AFR is.  I may try correcting the meter, but most likely its ending up in the trash soon...           

Alrighty Doug found the thread and will watch it now!  My Mini Cruiser was 1985/6 and as I said in the call, it was an easy bolt on with one small catch.  My donor parts were from a 1991 Winnie if memory serves correctly.  I think it was the balljoints I had to reuse?  I will try and dig up the specific information out of my old posts.  But you seem to have a pretty good idea of the direction/issues you are going in.