92 overheating in idle and city drive only

[dlmo78]

My 92 is pure stock 4.0 V6 motor, transmission, and 4X4. The truck will do fine on highway staying at the "no" part of the word normal on the temp gauge. When I get off the highway, I start going into the "hot" part of gauge and will cool rapidly when moving again.

So far, I have:
Flushed radiator in Feb using Valvoline oil change services (I did oil at same time),
replaced the fan and fan clutch,
burped (today) the system (even though that should have been good from the pro flush at Valvoline)

other possibilities are:

water pump (but it's not leaking and the burp proved its circulating the fluid)
thermostat (but it stays cool on highway)
hoses (they look and feel like they are in good condition)

Please tell me what am I missing?

 

[Roadrunner777]

I'm looking into a possibility. Can you say what, if anything was done or happened at about the same time you noticed the overheating?

 

[dlmo78]

I haven't had any other symptoms other than truck stays cool on highway and overheats in idle and city. I noticed the problem in late January and have been working on it as I have money to do so as well as babying the truck until fixed. I've owned truck since October 2010 and the motor came from a 94 California truck with a Pushrod V6 (same motor I had). My truck is an eastern truck so the California smog crap isn't hook-upped to allow motor to run smoothly.

 

[Roadrunner777]

Any symptoms other than the gauge reading?

 

[Roadrunner777]

In doing the engine work, did you re-install the radiator shrouds?

Also, what would you say is the spacing, roughly, fan to radiator?

 

[dlmo78]

radiator shrouds? Are you referring to the shroud that goes around the fan? If so yes. The fan and radiator are stock in size and distance. Whole truck is stock other than motor swap with another stock motor. Other symptoms is that sometimes the check engine light comes on and stays on when in "hot" zone, but I can pull over and turn truck off and on then it clears. I don't hear any unusual noises in the motor. I have also look through the fins of the radiator to see if they are plugged and they look fine.

 

[Roadrunner777]

You may just need to burp the system some more. This could also be a sticky thermostat. I would re-burp and see if it changes the behavior at all. Otherwise, my next step would be the thermostat.

After that then I have to come back and dig harder on why the fan is not effectively cooling the radiator. And if I did that, I would probably think about this engine coming from a different model vehicle, and maybe the fan spacing or speed isn't what it should be. Or maybe somewhere along the way with the belts and fan installation, something is turning backwards. If you are not absolutely sure, please make sure the fan and water pump are turning the correct direction. I know you have this right, but just in case others find this thread.

 

[dlmo78]

Ok I'll go to auto store and buy more coolant and a thermostat. I'll let you know what happens. The motor from the 94 was from a 2dr 2X4 with a 5spd. Western Auto asked me if my Transmission was an auto or manual when I bought the fan and clutch.

 

[DV8]

my x was doing something similar. it wasnt going all the way in the hot, but it was getting to hot for me to feel comfortable. i swapped in a 180° t-stat, and the problem was solved. i actually have better heat now than i did, and she warms up faster. also, with the 190° that the PO installed, while under heavy acceleration on the highway, the valves would rattle a good bit. swapped in the 180° and she rattles no more...

 

[Jason94sport]

I have similar behavior. It's heat soak. I have replaced fan & clutch, hoses, 180 tstat, coolant temp sensor, gauge sensor, heater core, & radiator. And I still get a rising temp gauge when I sit in traffic or idle with the AC on in the heat of South FLA. Doesn't go past m in normal though. I use 70/30 water to coolant & water wetter.
When I'm driving or the AC is off & it's not as hot out, it barley gets to N in normal.

 

[Roadrunner777]

You replaced everything except the flux capacitor. I might start thinking electric fan with an adjustable controller. Did either of you replace the bottom radiator hose? Did it have a spring inside?

 

[dlmo78]

KK, I replaced the t-stat and still same problem. I'm out of money atm so I'll work on it some more next week.

 

[Jason94sport]

I replaced all the hoses. The replacement did not have a spring inside it.

 

[arcblue]

I had the same problem last year after a coolant change, though it never got to "hot"....just a bit past the centreline...thought perhaps there was air in the system still, but I'm not sure. It's been fine all winter, but of course it hasn't been very warm outside. I have a reasonably new radiator, water pump, thermostat & temp sender, so I hope something isn't failing already.

I don't know what it is about thermostats on my X, but I have changed mine like 5 times over the life of the car...it seems a bit excessive...

 

[Roadrunner777]

I'm out of reasonable ideas, and I'm not going to send anyone to buy parts on my guesses.

But, to recap, when driving city, it gets hotter than it used to, and suddenly cools, cycling back to hot. It stays more in the center of the gauge during highway driving. There are no symptoms other than gauge readings.

The problem was first noticed in January. There was no related work or related events at that time. dlmo78, there is a branch in troubleshooting here, so I want to be completely clear, maybe over-doing it, but please confirm this engine did not experience anything like this prior to January, that it did not do this at all, say, back in August. If it is possible this engine had the problem before you installed it, we need to look at other things.

The engine is new to the truck, but well before symptoms began. Some emissions equipment is disabled, but again, well before symptoms began.

The fact that it suddenly cools rules out everything relative to the radiator and fan because, when the thermostat trips, there is a cool charge waiting in the radiator, hence the sudden drop in temperature. If you wanted to reduce the point where the thermostat trips, then put in a cooler thermostat.

Scanning other threads brought more information. Please search this section using the word 'burp' and you will find many people with similar problems. I see suggestions that people use dealership thermostats, and apparently, they should have a small weep hole in them. Be sure to install it so the big spring is facing into the block.

I would also look at other people's methods for burping. You may find another method, release a big old air bubble, and you are done.

 

[huntman58]

When mine did this the one thing that did fix it was a replacement water pump. The fins on the pump were some what rotted off so it was moving water but not at a rate that was needed especially at slow speeds. the only reason it stayed cooler at speed was from the ram air flow helping keep it cooler then just the fan at slow speed. Not saying this is what you’re dealing with but its some thing to think about and test for. you will not leak or show any real sings if this is the case but I for one am not for just throwing parts hoping to fix some thing I like to know by ruling out every thing other first and then doing all testing I can to still make sure. Also a collapsing hose can also do this. Again just some thoughts.

 

[Roadrunner777]

You know, I really like the waterpump answer. The problem is that it has been replaced in an attempt to fix the problem already. I think I remember reading somewhere about rebuilt pumps in the wild with an impeller issue, where it was not positioned correctly on the pump shaft. And, I also thought maybe because some smog equipment is disabled, maybe he is running a different belt pattern, and just possibly turning the pump backwards. I think we ruled that out.

I liked the collaped bottom radiator hose, but new hoses since the problem, and it looks like these do not use the spring insert.

I had a very similar issue once on a Ford Contour. Some contour water pumps use a composite (non-metallic) impeller that had a tendancy to shatter. One could end up with fragments floating around and blocking flow, causing this kind of issue. Explorer is a metal impeller, I gather, so that's good because it's pretty much impossible to get to the fragments.

The guy that knows how to fix this is an old guy that has been running a radiator shop for 25 years, and knows nothing but cooling system.

I don't think this is an Explorer-unique problem. I would look around the internet for ways to check water-pump flow, basic cooling system diagnostics. I might even get a cheap aftermarket temp sensor and get some accurate number readings. You are seeing different behavior of the gauge, with no other symptoms. It could just be the gauge!