(800) 853-2651
SHOP NOW

3.7 engine temp help

O

Old560

Member
I have a Dodge Ram 2003 3.7 I was driving down the interstate came to a hill trany would kick out of overdrive and engine RPM goes up temperature would drop on the gauge start blowing cooler air when the transmission goes back into overdrive and the engine RPM drops back down Engine temperature goes up starts blowing warm air second thermostat still doesn't make a difference any suggestions? it's always related to engine RPM
 
Your symptoms seem to contradict each other. Lack of heat from the heater would indicate either low coolant level or low flow rate. Conversely, low coolant would cause the engine temp to rise rather than fall. Low flow rate could be caused by corroded impeller on the coolant pump (commonly referred to as a water pump).
There is also a possibility of a collapsing hose, but again, that should show a rise in engine temperature.
Replacing thermostat after thermostat apparently does not solve the problem.
As much as the problem might indicate otherwise, my gut feeling is a corroded impeller on the coolant pump.
 
If it is blowing cooler but not cold air along with what you say about the temp going back to normal at normal driving RPM it would suggest the clutch on the fan is seized causing more air flow than is required.
Does the engine sound a bit louder than normal?
Kind of a dull roar that increases with engine speed?
Engine off and cold, try spinning the fan blades, if it is quite hard to turn then likely the clutch has had it.
 
Another thought did you by chance install what is often called a fail safe thermostat?
The nature of the design of these causes them to lock open once they get too hot, after this happens they no longer open and close to regulate coolant temp.
 
Does that model have a blend door controlled by vacuum? It seems the temp is changing when the engine vacuum does.
 

Not clear on exactly what you are referring to....

Is it Heater Heat, or are you concerned about engine Temps..??

If you are driving in profoundly Mountainous areas, the Trans should be dropping out of Overdrive on steeper grades on it's own..

If not, you may want to manually drop out of Overdrive or have the Shift-Points checked at a shop..

Today's cars will shift and hang onto a gear sometimes down to 1,200 RPM, that is fine on level roads, but WILL cook a transmission and Over-drive if
allowed to remain in that condition, or any like it on STEEP Grades...

Maybe you have some other problem, but ya never know anymore just what a driver knows...!!!

Ron..
 
Engine RPM drops engine temperature stays normal as Engine RPM rises engine temperature drops temperature gage will drop all the way down to the cold position and then the heaters Puts out cooler air. I've checked the fan clutch it seems to be fine compared to other fan clutches. The last thermostat came from Napa I'm sure it wasn't a failsafe thermostat. Coolant pump I could check the last time that was replaced. it's just weird the way this is operating. Temperature was -7 this morning and I don't use the truck very often. thanks for the help
 
(quoted from post at 13:16:33 12/28/15) Engine RPM drops engine temperature stays normal as Engine RPM rises engine temperature drops temperature gage will drop all the way down to the cold position and then the heaters Puts out cooler air. I've checked the fan clutch it seems to be fine compared to other fan clutches. The last thermostat came from Napa I'm sure it wasn't a failsafe thermostat. Coolant pump I could check the last time that was replaced. it's just weird the way this is operating. Temperature was -7 this morning and I don't use the truck very often. thanks for the help
Click to expand...
Gauge and heater temp output sound like they are moving parallel so we can rule out a faulty gauge or sending unit.

Low coolant level would be possible cause of low heat when accelerating hard up a hill. The higher RPM combined with the increased angle can lower the level of coolant thus starving flow to the heater core, the level in intake coolant passage may drop lower than the sending unit thus giving a false reading,

Low coolant.
Stuck thermostat.
Upside down thermostat.
Defective thermostat.
Fan clutch issue.

Not much else in the equation, start with double checking the coolant level.
If you are sure the fan clutch is good your next step would be go back to the basics.
Pull the thermostat, put it and a thermometer in a pot of water on the stove and verify the temperature it is opening and closing at.

A proper functioning thermostat is there to keep your engine warm just as much as it is there to keep it cool.
 
An engine will run cooler reving up a bit in a lower gear than lugging in a higher gear. If thermostat is stuck this could cause the symptoms you are describing.
 
That's what I was wondering. A thermostat that is set too cool (like a 160) instead of the 180 (or is it 190?) like a 3.7 should have might give you those results. Especially if you have a half clogged heater core.


I have a similar issue with my son's Bronco. The previous owner filled the radiator with stop leak then eventually switched the radiator out when it kept leaking. The problem is the heater core now has reduced flow - on the coldest days it never blows hot, his solution was to block off the grill to "make" it get hot.
 
You must log in or register to reply here.

Similar threads

Hemmjo
worrysome 860 engine noise
Replies
11
Views
579
Jeff Hamilton
J
C
99 problems and my tractor is every one of them
2
Replies
25
Views
1K
Coopdaloop
C
V
new owner of a 620, will try to update this as we go.
2 3 4
Replies
61
Views
4K
valiant8086
V
N
T0-30 Running hot under load
Replies
13
Views
989
Jerry/MT
J
R
Slow hydraulic pressure buildup
Replies
5
Views
899
Tx Jim
Tx Jim
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top