94’ 3.0 Intermittent coolant temp fluctuations and leaks. Please help!

[GabrielAlves]

Hello! I have a 1994 Ranger 3.0 that recently had a water pump replaced. I also replaced the fan clutch and the thermostat. Recently, especially on the freeway or under load, the truck seems to get hot really quickly when coming off the gas or in neutral, then slowly goes back down to operating temp. Usually the truck cruises around the “N” or “O” of the coolant temp gauge, but it will rise up around “A” or “L” when it’s at its worst. The coolant cap also likes to piss coolant everywhere despite the fact I’ve replaced the cap twice.

The only other issue i’ve seen is a small leak from the gasket area. I also want to try to replace the thermostat, since the replacement I put in was a cheap Gates model. Any insight please? Thank you!

 

[franklin2]

I don't like the Ford gauges. I have seen a lot of money and time wasted on what they say. They are very slow and you have no idea what temp you are actually running at. Some people do not like gauges hanging under the dash, but a cheap set of aftermarket mechanical gauges from the store would be a good investment if you really care about monitoring your engine.

On your leak, do you know where it's leaking? Make sure the hose and clamp going to the overflow bottle is not cracked. If it's leaking between the cap and the top of the radiator, then you will never build pressure in the radiator, and that can let it boil over on a hot day.

 

[MaicoDoug]

Gabe-
The worst thing any watercooled engine can deal with is bad head gaskets. They can leak combustion gasses into the water stream. There is a test you can do to detect combustion gasses in the collant. Also another test that looks at the leak down rate of a pressurized coolant system. Either of these potential leak points of failure can & will cause erroneous spikes in a water temp reading. You don't want a water temp gauge seeing 220 degree pockets of air, which it often does see. Thats is why the Ford factory dampens the display's reading.

The simple fact is your truck had/has cooling issues. That combined with damage from that ongoing episode of a cooling system failure. Don't rule out a warped head & failing head gasket. Often happens together.

The cap only is half of the sealing hardware, suspect the radiator fill neck also, however cheap china junk is taking us all down. Buy at Napa, their cheap china junk is better than most.

 

[GabrielAlves]

I don't like the Ford gauges. I have seen a lot of money and time wasted on what they say. They are very slow and you have no idea what temp you are actually running at. Some people do not like gauges hanging under the dash, but a cheap set of aftermarket mechanical gauges from the store would be a good investment if you really care about monitoring your engine.

On your leak, do you know where it's leaking? Make sure the hose and clamp going to the overflow bottle is not cracked. If it's leaking between the cap and the top of the radiator, then you will never build pressure in the radiator, and that can let it boil over on a hot day.

For the leak, it’s on the gasket sealing surface of the water pump, whoever installed it didn’t seal it up good luck guess.
I have thought about getting both coolant and oil pressure gauges, there is just a lot of things i’d wanna fix before justifying that, but I’m not sure. Thank you!

 

[GabrielAlves]

Gabe-
The worst thing any watercooled engine can deal with is bad head gaskets. They can leak combustion gasses into the water stream. There is a test you can do to detect combustion gasses in the collant. Also another test that looks at the leak down rate of a pressurized coolant system. Either of these potential leak points of failure can & will cause erroneous spikes in a water temp reading. You don't want a water temp gauge seeing 220 degree pockets of air, which it often does see. Thats is why the Ford factory dampens the display's reading.

The simple fact is your truck had/has cooling issues. That combined with damage from that ongoing episode of a cooling system failure. Don't rule out a warped head & failing head gasket. Often happens together.

The cap only is half of the sealing hardware, suspect the radiator fill neck also, however cheap china junk is taking us all down. Buy at Napa, their cheap china junk is better than most.

I’ve been suspecting a head gasket, but I’m just not 100% sure, are there any particular symptoms i could look out for? The oil is perfectly clean, and there isn’t any coolant smell from the exhaust. Would the only way to tell be the coolant exhaust gas test?
As for the Radiator neck, it just confuses me, since it worked perfectly fine before, but i haven’t ruled that out either.
Either way, thank you!

 

[MaicoDoug]

To T-shoot a head gasket issue, yes the combustion test is a quick way, or, try some head gasket sealant in a can type additive. I don't know where you'd need to put it however~? I believe a mechanic can do the test, perhaps one of the big parts stores may do that test for you rather than buy the whole kit.

For that leaking water pump, going to go out on a limb here.... never use any silicone on any pressurized system. Sorry it simply doesn't last. I use the thickest grease I can find. Permatex makes something that won't harden, thought you'll sprain your thumb attempting to spread it around, works always. There is also something that the Germans use on the BMWs & alike too. Super thick grease.

 

[Eddo Rogue]

might have air bubble stick in there and need to burp it. Park on a hill and let it warm up no cap and watch until the big bubble burp out then cap it. Mine took a few tries to get all the bubbles out.

 

[Airdre]

Sounds like your cooling system might not be fully pressurized or there's an issue with air pockets in the system. If the coolant cap is still leaking after being replaced, it might not be sealing properly, or there could be a deeper problem like a radiator or hose issue. You could try bleeding the cooling system to get rid of any air trapped. Also, replacing the thermostat with a higher-quality one could help. Since you mentioned a small leak from the gasket, you might want to keep an eye on that, as it could cause further cooling issues.

 

[Eddo Rogue]

+1 what @Airdre said. Might be sucking or losing air somewhere. I think mine was from the lower intake gasket. Been moving normal since I did that...by which I mean mostly in the middle, but varies a little according to driving conditions.

 

[GabrielAlves]

Update!

I replaced my thermostat, upon testing the older one, it hardly opened when under boiling water for 5 minutes. When I took a test drive, the temperatures seemed to be much more reasonable and consistent, so I’m feeling more hopeful! I plan on keeping an eye on the coolant level, and eventually I would like to test for combustion gases just to be safe. But for now I’m feeling pretty good. Thanks y’all!

 

[franklin2]

For that leaking water pump, going to go out on a limb here.... never use any silicone on any pressurized system. Sorry it simply doesn't last. I use the thickest grease I can find. Permatex makes something that won't harden, thought you'll sprain your thumb attempting to spread it around, works always. There is also something that the Germans use on the BMWs & alike too. Super thick grease.

You should use something when sealing water on a older engine. The cooling system uses a lot of alloy and aluminum components, and these tend to erode and pit when they get older. The silicone or whatever you choose to use helps seal up these pitted areas. Not sure I would depend on grease to last on a very eroded pitted area.