Dumb Question of the Day

[NMC_EXP]

My DD is a '97 Ranger with a 4.0L V6, 5 spd. It has 109K miles on it.

Couple of years ago it started dribbling coolant on the driveway - leave a 6" dia spot every time I parked it. Deal is I'm 73 YOA and crippled up so I cannot crawl under it to eyeball the cause. My local mechanic replaced the heater control valve and some heater hoses but he was not convinced that was the fix - it was not.

The spot on the driveway is under the right side of the engine about half way between the front of the block and the firewall. I know that a leak can run down and drip places not directly under where they came from.

Anyhow the deal is 10 days ago the overflow tank was empty but cold the radiator was full up to the cap. I refilled the overflow tank. Couple of days ago just driving aroung town the temp gage came up to normal but then would drop down to the bottom of the normal range, after a while go back to normal. This makes me think I have an air pocket in the cooling circuit even though the radiator was full to the top when cold. This is the third time this has happened.

Question:
(1) I know the overflow tank was intended to catch radiator overflow if it was overfilled or overheated then boiled over. My question is if the radiator is low can it siphon coolant back from the overflow tank to the radiator? If not I think maybe the overflow tank is leaking but I just can't see it.

Remembering back when I used to work on my own vehicles I recall you could check a radiator cold and it was full. With the cap off let the engine warm fully up and at first if would puke some coolant out over the top then then I suppose when the thermostat opened up the air pocket would hit the radiator and coolant level would drop out of sight - then you would fill the radiator to the top and put the cap on. Am I thinking right on that?

I hate to replace the coolant recovery tank based on just a wild guess. I should add no sign of a blown head gasket.

Thanks in advance.

Jim

 

[RangerNumber3]

My guess for the 4.0 that its the water pump or the timing chain cover.

 

[NMC_EXP]

My guess for the 4.0 that its the water pump or the timing chain cover.

Not good news but I appreciate it.

Jim

 

[SenorNoob]

I usually have to fill the expansion tank 2-3 times after refilling the engine. I've learned to just fill it to the top the 1st time. That usually gets all the air out after one heating/cooling cycle.

That said. I'd be looking at the tank and hoses. Had a similar problem on Brittney's car and just needed to add a clamp to the hose from the expansion tank.

 

[NMC_EXP]

I appreciate the reply.

Jim

 

[Snoranger]

The way a coolant reservoir/ overflow tank works is…

When the coolant heats up, it expands. It pushes some fluid past the radiator cap and goes into the reservoir. When the engine is shut off and cools, it forms a vacuum and sucks that fluid back into the coolant system.

In a perfect world, there’s no fluid loss and the levels always return to the same points.

 

[Brain75]

+1 to the above /\ with caveats... So old systems (like my '48) which had no coolant overflow tank you left a big chunk of space at the top, then later systems the "overflow" tank was just that for overflow it was basically a one way puke out and never draw back in. I'm betting the OP is most familiar with this style. Modern systems pull and push from the "overflow" tank (which is not really an overflow it is a buffer reservoir). My GM vehicle has a horrific 'coolant bleed procedure' (to purge air bubbles) I learned about when I had to change the water pump. From a few threads here on TRS, I learned that the easiest way to bleed the air bubbles on a ranger is to put the front up on stands, run the system a couple thermostat cycles while being very careful to keeping the tank from running dry with the HVAC set to heat.

Is there really no bleed screw/plug on the engine (just like my gawd awful GM) ?

 

[Brain75]

couple posts to note:

Bleeding Cooling System?

Replaced my leaking T-stat yesterday on my '95 4.0L. Drained all of the coolant and replaced with new. Now, the engine is overheating and the heat is blowing cold. I assume there's some air in the lines, but I can't find a bleed valve or anything. What's the best way to bleed the air? Thanks!

www.therangerstation.com

post #2 here:

cooling sysrem bleed valve 02 explorer 4.0 - Ford Truck Enthusiasts Forums

Explorer, Sport Trac, Mountaineer & Aviator - cooling sysrem bleed valve 02 explorer 4.0 - does anyone know where the cooling system bleed valve is on this model?

www.ford-trucks.com

 

[Shran]

Remembering back when I used to work on my own vehicles I recall you could check a radiator cold and it was full. With the cap off let the engine warm fully up and at first if would puke some coolant out over the top then then I suppose when the thermostat opened up the air pocket would hit the radiator and coolant level would drop out of sight - then you would fill the radiator to the top and put the cap on. Am I thinking right on that?

I bleed 4.0 cooling systems by removing the cap (engine cold) and start it and let it run for a bit. If it's low to begin with, I will operate the throttle by hand under the hood and run the engine at 2-3000RPM while filling the radiator. The water pump will suck the coolant level down and you can fill it right to the top. Before you let off the throttle, put the cap back on. Most of the time you are good to go at that point but if you have replaced a major component that required the coolant to be drained, you may need to do this twice, once before and once after the thermostat has opened. Sometimes you can just let it cool off, top it off, and be fine though. Just depends on how much air was trapped behind the thermostat. Should be very little if the jiggle valve in the stat is working/oriented correctly.

Also by right side, do you mean passenger side? Lots of things to leak coolant there. Not so much on the driver's side.

 

[NMC_EXP]

I mean passenger side = right side. Yup - there is a lot of plumbing over there.

Thanks for the info.

Jim

 

[gaz]

@NMC_EXP
I put double clamps on both ends of the upper/lower radiator hoses; I would give a good hard look to the thermostat housing and water pump, while idling, before you take it apart.