2.9L & 3.0L V6 Tech General discussion of 2.9L and 3.0L V6 Ford Ranger engines.

Mystery overheating

Old 11-02-2018
ValSellsHomes's Avatar
Thread Starter
Join Date: Nov 2018
Location: Cedar Creek
Posts: 7
Mystery overheating

I have a 1989 2.9 that I have put a new transmission, muffler, radiator, thermostat, temp sensor, sending unit, air filter on. The truck was getting hot when I got it a few months ago. It didn't have a muffler on it at the time. I thought that was causing the heat issue. Then the tranny went out. I had a brand new tranny and muffler installed at the same time. After that was still getting too warm, but not as much. I put new radiator in it last weekend. The new radiator made huge difference. The gauge hardly moved. That was almost a week ago. I noticed this morning however in just the 5 miles it took to get to work that the temp was going up quite a bit, nearly out of the normal range. I checked the coolant level and had to add a little over 1/2 gallon back to the radiator. I do not have any leaks. The truck starts, and runs great, no water or white smoke from the exhaust, no water in the oil. I know all of that sounds like a blown head gasket. I do however smell antifreeze after driving. It is also hard to start after it gets hot. Don't know if these two issues are related. Before I go tearing apart the engine I'd like some input.
Old 11-02-2018
RF Veteran
iTrader: (1)
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 12,579
Welcome to the forum

Your Ranger uses an overflow/recovery cooling system
As any fluid is warmed up it expands in volume, and when it cools back down is shrinks in volume, and coolant does this in your engine

This is where the Pressure in the cooling system comes from

The Radiator cap has TWO valves, the larger one with bigger spring holds pressure in the radiator/engine until it gets to 14psi
At over 14psi the larger valve is pushed open and warm coolant flows to the Overflow tank, until pressure is under 14psi, this should happen every time you drive more than 15-20minutes

After engine is shut off and coolant starts to cool down it will shrink in volume, and pressure in the system will go down, if warm coolant was sent over to the overflow tank, then pressure will drop BELOW 0psi, this will cause the 2nd smaller valve in the center of the cap to be pulled open, and coolant will be sucked back in to radiator from the overflow tank.

This is why the overflow hose is connected to the BOTTOM of the overflow tank, so it pulls in only coolant.
And this system is self purging of air
If there was air in the engine/radiator the circulation of the coolant would eventually get all the air to top of radiator, then as coolant expanded and rad cap opened the AIR would be pushed out FIRST and into the overflow tank where it would bubble to the top and be gone.
On cool down coolant would be sucked back in to replace that air

So after engine is cooled down all the way when you open the radiator cap it should be filled to the TOP, no air at all
If there is air then there is a problem.

If there is a leak in the engine/radiator part of the system then it would leak coolant of course but it would also SUCK IN AIR on cool down because the air is easier to pull in than the coolant from the overflow tank.
If you smell coolant in the cab then heater core probably has a leak

Small coolant leaks may only start to leak when system has pressure, and that's after engine is hot, so if coolant leaks on a hot surface it won't drip to the ground under the truck, it evaporates so no sign of a leak

Overflow tank hose needs to be sealed, no cracks, or air would be sucked in as engine cooled down.

Since you did have to add coolant then either overflow system has a problem, sucking air instead of coolant, or you have a leak, only two options

Its possible to have a cracked head or head gasket issue, 2.9l was candidate for those
You can do the Glove Test, to take that off the table
Do a search on this site, Glove Test, I have posted it numerous times, very simple and easy test, 100% accurate

Last edited by RonD; 11-02-2018 at 11:54 AM.
Old 11-07-2018
ValSellsHomes's Avatar
Thread Starter
Join Date: Nov 2018
Location: Cedar Creek
Posts: 7
Testing and still no answer

Borrowed a block tester today from a friend. Test came up good. No signs of blown gasket. Tested it hot and after several minutes. I let it run for a while and the gauge hardly moved. I check out the overflow reservoir, hoses. All checked out good. I just dont get it. Where is all the water going?? I'm thinking about trying some block sealant in a can. I'm not inclined to pull the heads unless all else fails. There's not enough evidence to justify pulling the heads at this point.
Related Topics
Thread Starter
Last Post
SOHC - 2.3L & 2.5L Lima Engines
05-27-2009 09:38 PM
2.9L & 3.0L V6 Tech
10-05-2008 08:57 PM
2.3L & 2.5L I4 Tech
06-20-2008 04:00 PM
Drivetrain Tech
05-22-2008 08:22 PM
optikal illushun
General Technical & Electrical
01-02-2005 09:49 PM

Thread Tools
Search this Thread
Quick Reply: Mystery overheating

Contact Us - Sitemap - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.