benja455

I appreciate all the help, guys...I'm just amused by the difference in the replies I've got:

So...some people think it's normal (and experience the same thing) and some people think it's a problem.

Well, I'll replace the radiator at some point soon and hopefully that will resolve the issue. This Pickup isn't my daily driver and with the summer camping season coming to a close, it won't see much use unless we get another random snow storm up in Seattle this winter.

Thanks again!

vital22re

iTrader: (2)

My old 89 22re never did this. Even my sc'd 3.4 swapped 92 has never done this. And thats even if I'm running it super hard on the freeway/offroad/onroad.

Is it more noticeable if you're jumping off the freeway then shutting it down? or if you're just out driving around town then shut it down?

benja455

Vital,

Yes...the few times it's done this - it was a quick jump...50+ MPH to dead stop and turned off in less than 60 seconds. It hasn't happened if I take the street roads for a few minutes after getting off the highway.

ZUK

iTrader: (1)

I have to re-evaluate this......if your temps went towards the red WHILE you were on the highway doing 60 or so then I would say it's the radiator. At 60, there is a good load on the engine and plenty of wind passing thru the radiator so that would make it a radiator issue.

......But, if you are slowing down getting off the off-ramp....or it gets got in slow traffic like you said, then I now have to sway towards an airflow issue. This puts the fanclutch as the prime suspect....leafs or mud possibly in the fins?
Fan shroud is a suspect but you said you have a good one in there now.

benja455

My neighbor (a mechanic) said the same thing. He suspects the fan clutch. I'll still replace the radiator for at some point...but the fan clutch is the first thing.

abecedarian

The fan clutch would be the issue if it weren't able to lock up, so to speak, and drive the fan at full speed. If the clutch is locking up, the only other thing is the radiator not being able to shed heat efficiently. Or as I mentioned earlier is "borderline".

To which I will add, the few that don't believe coolant will "auto circulate" due to convection currents... you should have learned that in your high-school science classes. A temperature differential between two systems will result in a net transfer of heat so long as the transfer is not physically disallowed. Hot coolant (heat soak) in the engine may eventually raise the temperature of the fluid behind the thermostat sufficiently that it will open and allow the hot fluid to escape and the cooler fluid from the radiator to enter the system from below. Maybe if I said "heat rises, cold sinks" and that causes a net flow, the slow ones would understand? Probably not, but here's to hope.

Keith B.

Where the pointer on the gauge goes to depends not only on the coolant temp, but the sender and the gauge as well.
I had a sender that ran the gauge at about 1/4. Then I changed only the sender, and 'normal' now is just below 1/2 on the gauge.

Badger62811

OK I just want to bring this up again. I feel like we are missing a vital piece of information. The OP said the temp gauge is fine when the truck is running (idling, driving fast, driving slow) this tells me it is NOT a fan clutch issue, or a problem with air flow. He said he turns the engine off for a few minutes, turns the key back on, and the gauge is high. Once the engine is started, the gauge goes back down to a normal level.

How does an engine have a cooling problem when none of its components are activated? Maybe I'm just not as technically savvy as some of you folks, but it seems like this is not a problem.

Maybe it's also the fact that I work from 4am to 6 pm Mon-Fri and have 2 very short days a week to be with my family and get things taken care of around the house. I don't have time to chase my tail with "it could be this, this, this, or this." If it's not obvious what the problem is, I can't spend half a day trying to figure it out.

abecedarian

"Heat soak"

If the engine itself weren't hotter than 212F or so, the coolant would never get that hot. The coolant can only absorb as much heat as it can, based on how long it is in contact with the engine internals.

When you shut off the engine, the coolant coming out of the engine is around 190F or so, give or take, but the engine can be 250F or more. So, any coolant still in the engine is absorbing heat.

The gauge temp sender is on the intake manifold (on the 22r/re) between #2 and #3 cylinders. The thermostat is at the front of the engine by #1 cylinder.

Convection currents, the known tendency for fluids to circulate in order to attain equilibrium (which some people here don't seem to grasp) will cause the more-cool fluid from the radiator to enter the engine, and the hotter fluid from the engine to enter the radiator. Simple thermodynamics, actually.

If the radiator cannot radiate heat efficiently and passively (without the fan), or the thermostat isn't operating correctly, the convection currents will slow and maybe stop, and the coolant in the engine will become superheated (with respect to what's in the radiator). What does that mean? The temp gauge on the dash will spike when started- obviously since the engine is that hot, but it will quickly cool down once the coolant from the radiator rushes in... and not having the gauge sender next to the thermostat doesn't help either.

And if anyone wants to call "bollocks" on me, and you don't believe temperature differentials won't cause fluid flow, you better do so as well on Al Gore, the Atlantic Conveyor Belt (thermohaline circulation) and global warming.

01d's kool

It would help if you pull your rig into the breeze before shutting down.

_RaStA_RoCkEt_

Ah Such Knowledge abound this thread!

I've the exact same problem, albeit with more pronounced heating on hills or under load, and have rationalized it to the 'heat soak' Abecedarian is talking about. After reading through this thread, I feel like I should check into all my cooling system components to help cure this problem (Which, I too, believe is semi-unique to aging cooling system trucks)....

...But I have changed the Radiator for a 3 Row heavy duty, the T-Stat for a Toy. OEM 2 Barrel 180c Celica stat, Replaced the Water Pump with an Aisin model, and Added More Burping Points to the Heater Hoses to make 'bubbles in the coolant' a thing of the past... (ALL within 2000 Miles)
I could rationalize a clog somewhere... but there is no where left for a clog to hide. Unless it's in the engine's water jacket itself...

...yet my truck still does this.

Hmm....

Pat8942

Stick a piece of red hot metal in a container of water, the water gets hot absorbing the heat from the metal, do the same with water circulating in and out of the container and the water won't get very hot, same concept, ya can't fix physics nor any thermodynamic principles no matter how hard you try.

cubuff4runner

After reading this thread I feel like I need to replace every part of my cooling system, even though it is working fine.

Pat8942

My muffler bearings get hot if I let the truck sit for 3 months, I guess it's time to fix the Johnson Rod or at least modify it to be better than new.

Badger62811

LMAO me too. I feel like I should just replace my entire motor "just to prevent bigger issues down the road"

benja455

As an update...the radiator was replaced with an all aluminum 2-core, the hoses were replaced, the fan clutch was replaced, both sensors were replaced and the thermostat was replaced with the 2-stage unit recommended elsewhere on this board and others (http://www.4crawler.com/4x4/CheapTri...tml#Thermostat).

Everything functions pretty well and the truck idles much smoother now. The only issue I experience is a bit of temperature overshoot (which the 2-stage t-stat was supposed to prevent). The truck gets to the mid-point on the temp gauge and then whether sitting still or at highway speeds - it will work its way up to 7/10 (one time it was 8/10) on the gauge and then plummet back down to 4/10...stay there for a while and then randomly it will stay at 5/10 or repeat the process over again.

I'm thinking of going back to the original t-stat (with or without a drilled hole). If that doesn't resolve the issue - I'll be replacing the water pump. Thoughts?

vieroski

Sounds to me like you haven't properly filled your motor with coolant. I found this thread actually while searching on how 'burp' the system too.

My radiator is shot, and any time I put load on the truck I end up loosing coolant, nearly overheating, then need to fill/burp all over again. Whenever I am low on coolant I get strange things happening with the gauge, like it will stay nearly at the bottom while I am driving yet the heat will work great. I'll turn off the motor then come back a little later and find the gauge at normal temp. Start driving again and it goes back down slowly to almost the bottom. If I put load on the motor again without a properly filled radiator sometimes I get a temp spike, where the gauge will say everything is fine then suddenly it's in the red. My only guess here is that the coolant level is low enough that it doesn't reach the sensor until it boils over.

Check to make sure the system is filled fully and that there aren't any leaks, then see what happens.

dimitri

- deleted

dimitri

deleted -

benja455

Not sure why you deleted your previous comments as they were nice additions to this thread.

Anyway...so, here's an update: If I leave the HVAC off - the truck stays right below halfway...no matter what, up hills, in traffic, with a load in the bed...it runs right where it should. I can turn on the cold vent or defroster without an issue too. If I turn it on heat - that's when the temp gauge goes up. It seems to stop IMMEDIATELY after I turn the heat off.

Do you think I've got a bubble trapped in there or something? The heatercore doesn't seem to be blocked - it pushes out serious heat. I don't think I'm low on coolant - I've checked many times.

This problem is driving me crazy...