I just read through all the posts i could find on this mysterious overheat that 3 or 4 of us have had or are having. Im in a DII and my truck runs for 20 minutes perfectly then BAM! all the way to red light, replaced all the hoses which were old, new t stat, new radiator, no oil in the water or visa versa, overflow tank looks like it may need a cap, and I havnt touched the water pump (140K)...And one of the threads talked about no heat and I have that symptom also ???? Heads were ALLEDGEDLY done at 113K and plugs seem to be fine but I do get rough idle and a little water at exhaust at startup? also noticed a comment about pump possibly running backwards??? I was under the notion that the belt only ran one way and if you missed a pulley or went on the wrong side it doesnt fit? SO...go for the pump first, dbl check the serpentine replace the overflow cap...and Bleed again?? although Ive seen 2 different ways to bleed and heard 2 different types of coolant should be used. Straighten me out...LOL

 

Well, we have heard reports of bad thermostats if it is a OEM rover, and it is worth while to check your serpentine belt route. Start your truck with the coolant cap off. Are you getting a stream from the return line? Air can be the always be a issue. Raise your reservoir and then remove the bleeder on the top hose. Air or coolant? With the cap off let it reach operating temp with the cap off and heat all the way to high. start with some pretty straight forward trouble shooting.

 

Thanks...I willl follow try that method first before i rip the waterpump off..I also have no heat untill the rpm's are high??? one of the posts said this was an indication of low water pressure...
JAMES
99'DII
66"F100 (for towing DII)

 

Or possible air in the system. Seeing a good strong stream of coolant back to your reservoir is a good indicator your pump is working properly. I would even replace a thermostat before replacing a non-leaking, non-noise making water pump. Think British Atlantic has them on sale. So good coolant reservoir cap, good thermostatic, and no air in the system..them the pump. Also do a search on "radiator". If at some point someone has added a stop leak or even mixed dexcool with a different type of antifreeze it can gum up a radiator...and real bad to. When flushing you can put a water hose in the top inlet and watch at the bottom for flow. It should flow freely.

 

Thanks ...Im in the middle of trying that right now and I do not get a stream back into the res when the motor is running with the cap off???? and by the way RAVE says glycol based coolant ?? so do I use DEX or standard Glycol based antifreeze?? Seems to me some confusion on my part.

 

You can use any coolant safe for aluminum, green Peak will also work. Just don't mix different types of coolant, dexcool is notorious for screwing things up.
There are 2 returns going back to your reservoir, one from the throttle body heater and one from the top left of your rad. Maybe your throttle body heater is blocked up, a common problem.

 

X2...

 

Okay I followed your advice and guess what? nothing but a weak dribble coming out of the return line to the tank. This probably explains my heating issue also. I ordered a new cap from Atlantic B. along with a tstat to be safe, and yes the water pumps are on sale. Oh yeah the radiator was from a 50K wreck, I ran water through it before I installed it and it was good, along with my serpentine belt...it is running the right way....THANKS again for setting me straight, Ill let you know how t all works!
JAMES

 

Your throttle body heater is blocked. Check the area around your throttle body heater for signs of coolant leaks, or orange stains.
You can test this by bypassing the TB heater and see if you get a flow in the tank.

 

How can you un-block the throttle body? thanks!