temp gauge going up and down

[walleyesteve]

put in new water pump and timing chain cover and my truck will idle fine and hold temp but when i drive it drops to just under cold then works its way back to normal then i noticed i had a pulsating from the top rad hose and heater hoses pretty bad the truck never overheats or pushes coolant out i am at a loss as to what to do please help its a 1999 ranger xlt 4.0 4x4 thank you

 

[infantry grunt]

thermostat stuck open,maybe?

 

[walleyesteve]

just put new thermostat on truck stant with a weep hole to get air out and put new radiator cap on took for a ride today but thermostat gauge still went down after driving it then back up but no pulsating from the hoses yet keeping fingers crossed i can deal with gauge up n down but the hoses i cant ill keep you updated thank you

 

[cowboykilroy]

while you are driving run your heater, if the air gets cooler at the same time your temp gauge drops you still have air in the system. sometimes they can be difficult to bleed.

 

[walleyesteve]

thank you i will try that tonite it pulsated again when i pulled in garage and shut it off but not as bad as before but i started truck up again and then shut it off and it stopped

 

[walleyesteve]

one other thing i havent tried yet is putting a new upper hose on the radiator it is kinda soft when i squeeze it maybe its collapsing under the pressure and that is where pulsating is coming from let u know please keep help coming in meantime thanks

 

[JustME]

I have noticed that the temp. gauge on my 96 Explorer, once I am at operating temp., will go from reading 2/3rds up the gauge to 1/3rd then back again. I think it might be a sticking thermostat but nothing seems to be affected. Unless it causes problems it can wait til warmer weather when I won't be driving it as often.

 

[35Remmy]

I have had this problem ever since I installed my remanned 4.0 a few months ago, and it only happens when the heat is on. I have done everything except change the heater core! There have been TSB's on it, from installing a heater thump service kit to increase flow (steam builds up and gets trapped in the core) to a redesigned water pump from ford. The service kit is no longer available, of course.

I would also think that a partially clogged core could cause this (flow reduction), or a core that is leaking ever so slightly to suck in air as the engine cools off. Problem is annoying, and these trucks obviously didn't do this from the factory new.

 

[pcollins]

Get a real temperature gauge.

 

[BLUTHUNDER1]

replace heater core

Replace your heater core after you replace it make sure all air bubbles are out of system. fill recovery tank let it cool refill to proper level . If it still does it use cooling system pressure tester to ensure you have no leaks you can get a loan a tool cooling system tester from autozone .

 

[35Remmy]

Collins, I have that covered too. Installed Autometer Pro-Comp water temp and oil presure gauges. Also replaced both coolant temp sensors.

I did have the system pressure tested and it was ok.

I may take the heater control valve out of the picture and just couple the hoses together. It has to restrict flow to a certain degree; I'd rather try this before changing out the heater core. Not as easy as my 88 that takes 20 minutes to change.

The heater thump service kit was essentially a new lower radiator hose that had another hose coming out of it that attached to a t-fitting which screws in to where the current coolant temperature sensor is on the upper intake...on the right side. You attach your temp sensor to the backside and the new hose to the frontside.

Very simple, and is supposed to improve flow in the system. I'm not certain how this setup does this, I wish I had a coolant flow diagram for this engine. Have thought about making it myself, it's certainly a possibility and wouldnt cost much.

 

[shane96ranger]

I went through several of these fixes you guys are talking about on my Explorer. I went through several different scenarios of t-stats, radiator caps, aftermarket gauge, etc. before I finally replaced the fan clutch. That fixed my surging gauge.

 

[35Remmy]

Did you get a temperature surge only with the heat on? With the heat off, my temp runs a pretty firm 195 give or take a few degrees.

When the thumping starts, especially after turning off the truck, I can put my hand on the plastic assembly that covers the heater core on the passenger side inside the cab and feel the thumping right there.

Ive just been running without the heat...I dont like temp surges like that for the sake of the cylinder heads, although they are thicker aftermarket castings.

Oh, and Redline water wetter (to reduce steam formation and increase coolant surface area contact) has done nothing.

 

[walleyesteve]

i am still having the temp up n down and surging of hoses but it is only when the heater is on to the guy that said he fixed it with new fan clutch did your explorer only have problems with surging with heat on or off or both more help please