Radiator temp

needlenose

Full Access Member
Joined
Dec 9, 2013
Posts
399
Reaction score
87
Location
Irrelevant Data
I'm curious, has anyone ever felt the temp of their radiator top to bottom after driving. My truck is cycling hot/cold on the gauge when it should be steady. The rad is full, the top is smoking hot, but the bottom is ice cold. I mean there is no heat in the lower hose whatsoever. The thermo is brand new. The radiator is about 1.5 years old and the hoses are about a year old. The pump is about a year old as well. I'm running the aluminum Spectra.

Maybe the water at the bottom is supposed to be cold, I've never thought to feel the rad at the bottom. But I would think it would at least be warm after an hours driving.

Starting to wonder if I don't have a blockage in the radiator.
 

shawn deere

So many wrenches, so little time...
Joined
Dec 29, 2016
Posts
445
Reaction score
82
Location
nebraska
Did this just start after you teplaced something? Theres a little check in the thermostat housing i believe designed to let the air purge its self out. If thats blocked and theres air in the system the water pump could lose its prime.

Also might be indicative of a blow head gasket pushing combistion into the cooling system causing the same effect

Does the coolant look like coffee?
 

Macrobb

Full Access Member
Joined
Jun 12, 2016
Posts
2,380
Reaction score
1,234
Location
North Idaho
So... First, I wouldn't trust the gauge. Get an aftermarket gauge, even a cheap one will do. I prefer electrical sender-type gauges over capilary-tube mechanical ones.

Second, if you aren't towing, I expect this sort of temperature differential. The engine just plain doesn't put out enough waste heat to keep the thermostat open unless you are towing a trailer or going up a long hill at high speed. As such, it cycles. The temps should stay in the 180-190F range unloaded, when measured at the factory sender location.

Loaded, it may climb a bit, but up to 220F should be OK. I've only had temps like that when hauling a heavy trailer up a really long, steep grade going 60-70MPH with a turbo and far more fuel than stock.

Thirdly, where did the new thermostat come from? If it's not a motorcraft one... go get a motorcraft one and swap it out. The cheap ones tend to break, and often don't fit right. The motorcraft one isn't expensive, either.

Also, if you have to get back in there, remove the little ball bearing from the upper housing piece. This will give you a 1/4" channel bypassing the thermostat, which /really/ helps in bleeding. It also does not seem to affect the time it takes to get up to temperature, so I consider it a good mod.
 

icanfixall

Official GMM hand model
Joined
Apr 10, 2005
Posts
25,858
Reaction score
672
Location
West coast
So the thermostat is new but.. What type did you install??? If it is anything other than an original motorcraft part you made a huge mistake. Please tell us what was installed for more help.
 

IDIBRONCO

IDIBRONCO
Joined
Feb 5, 2010
Posts
12,237
Reaction score
10,925
Location
edmond, ks
If it's really cold out, maybe the coolant is losing a lot of heat in the radiator.
 

needlenose

Full Access Member
Joined
Dec 9, 2013
Posts
399
Reaction score
87
Location
Irrelevant Data
Did this just start after you teplaced something?

It's kind of a long story. About a month or so ago we had a freeze that lasted for a couple of days. My truck developed a small drip from the lower rad hose at the fitting. There was plenty of antifreeze because there was a wet puddle on the ground in about 10deg weather. When it warmed up I crawled under and tightened the clamp; it wasn't very tight. The leak stopped. I topped up the radiator and all was good. Then it started cycling hot/cold. I figured it was air and tried bleeding the system. There was no air. I swapped the Napa thermostat for an OEM one. It seems better, but it still seems to cycle. Last night was the first time I ever crawled under and felt the hoses after driving it.

I was shocked how cold the bottom of the rad was. It was down in the low 40s and bottom of the rad and the hose felt about 40deg. I could barely put my hand on the top tank. I started it cold and this morning and tried the bleed screw again. I coated the entire engine bay with coolant when it went Ole Faithful on me. So the pump is not air locked. I need to just get a real temp gauge so I have actual numbers to refer to. The cheap Napa thermo was probably just stuck open all this time.
 

shawn deere

So many wrenches, so little time...
Joined
Dec 29, 2016
Posts
445
Reaction score
82
Location
nebraska
Yeah i would agree, a real temp gauge might be the fix. I caught my factory temp gauge wigging out on me the other day...
 

no mufflers

Supporting Member
Supporting Member
Joined
Jan 20, 2014
Posts
2,238
Reaction score
1,087
Location
rhode island
the temp gauge in my truck would act up. it would stay in the cold for a while or go in the hot zone, and then it would bounce back and fourth a lot. when I re did some of the wiring and put a new sender in along with an auto meter gauge it ended up working again and now reads accurate and is consistent with my other gauge.
 

MtnHaul

Supporting Member
Supporting Member
Joined
Nov 1, 2014
Posts
616
Reaction score
258
Location
California
Mechanical temp gauge gets my vote. Nothing beats seeing the actual temperature in numbers, not "between the O and the R".
 

Shawn MacAnanny

Full Access Member
Joined
Feb 12, 2016
Posts
818
Reaction score
44
Location
Delaware
My engine with all new cooling system was cool to the touch on the bottom, so less than probably 50f on a 20 to 30f day top was around 120-140 or so.

I run a winter cover on my psd it got up to 60f here today and I didn't take it off. oil temp stayed right at 205f and trans temp (runs through bottom of lower radiator) never got above 160f. These cooling systems are way oversized for unloaded loaded trucks
 

rhkcommander

Full Access Member
Joined
Feb 9, 2010
Posts
2,603
Reaction score
90
Location
Oregon
Back when I put in my engine without a mechanical fan, I used five computer fans hooked up to the new fan controller, while I was waiting for my dual electric fans. They did the trick and then some, monitored them with a pair of pc heat sensors just in case.

I wouldn't tow like that, but it was enough to keep from overheating at a dead stop. Moving, the airflow was enough. The ceramicoated exhaust really cut down on underhood temps a LOT though.
 

OLDBULL8

Good Morning Ya'll.
Supporting Member
Joined
Feb 12, 2009
Posts
9,923
Reaction score
338
Location
Delphos , Ohio
"Also, if you have to get back in there, remove the little ball bearing from the upper housing piece. This will give you a 1/4" channel bypassing the thermostat, which /really/ helps in bleeding. It also does not seem to affect the time it takes to get up to temperature, so I consider it a good mod."

Do not remove the air by pass ball, but it must move freely. It stays open until coolant reaches it, then closes.

You say the bottom of the rad is cold and top hot, highly unlikely the Rad is plugged, the is too many passages in it not to have some circulation. I would say your T'stat is in upside down or broken.
 

rhkcommander

Full Access Member
Joined
Feb 9, 2010
Posts
2,603
Reaction score
90
Location
Oregon
I agree with oldbull, clean the ball up and make sure it moves, you don't want that hole wide open. If it gets clogged you would blow a hose off, that's what my UHaul engine did the first time I warmed it up. Dirty ball, cleaned right up and was fine after.
 
Top