Cooling Issue

[limikjr]

Hey guys, I'm in need of some 3geez expertise. So here's the problem: When I take my radiator cap off and let the car warm up the coolant flows fine. Both hoses get warm, so I know coolant is getting into the engine. BUT when I warm up the car with the radiator cap on, only the top hose gets hot and the bottom hose stays cold. So, coolant can't make it out of the radiator with the cap on, but can with the cap off. I've bled it correctly, and replaced the cap and thermostat. Any idea what could cause this? Thanks.

[Dr_Snooz]

That is pretty much how the cooling system is supposed to work. Hot water goes into the top of the radiator and cools as it falls. When it gets to the bottom, it is returned to the engine for another cycle. The bottom hose should be cold. The system is designed to operate under pressure. Pressure raises the boiling point of the coolant and allows it to cool more effectively. When you remove the cap, it makes the system less efficient so you get both hoses heating up.

I'm sure this wasn't a theoretical question though. What's going on with your car that you are investigating the cooling system?

[limikjr]

It starts smoking when I sit for a minute or so in traffic, not a lot, just a little bit coming out the hood. Cooling fan never comes on by itself so I hard wired it and keep it on around town, but it still smokes. Plus when it starts to smoke it runs real rough. So because it still seems to overheat even with the fan on, I assume coolant isn't flowing.

[Dr_Snooz]

Do you actually smell coolant? Are you losing coolant? The oil seals on these cars like to spring leaks and must be changed every so often. If you're seeing smoke, I would think it's oil before I'd think it's coolant.

As for overheating, there are a lot of things it could be. Check the coolant level in the radiator first. If the cooling system hasn't been maintained well, then you should get that up to snuff too. Change the coolant and replace the thermostat. Check all your hoses to make sure they aren't leaking. If they are, get them replaced promptly. If you don't, they will eventually explode and you'll be stranded. When that happens, there's a very high likelihood that you'll blow the engine too. That's an expense you don't want. Get that done and if the problem continues, we'll go from there.

[limikjr]

I already did a complete flush so I'm good there, replaced the thermostat and radiator cap, and no the hoses are not leaking. So, on that note, you think the smoke could be oil? How should I go about diagnosing that? Thanks for all your help.

[car6289]

I already did a complete flush so I'm good there, replaced the thermostat and radiator cap, and no the hoses are not leaking. So, on that note, you think the smoke could be oil? How should I go about diagnosing that? Thanks for all your help.

Heat up some oil until it smokes, take a whiff.
Heat up some antifreeze/coolant until it smokes, take a whiff.

You are training your nose to tell the difference in smell between oil smoke and antifreeze/coolant smoke.

When you determine what is causing the smoke, it narrows down where to look for the leak(s).

[w261w261]

What is the temp gauge doing when all this is going on?

[w261w261]

Also, are you getting smells in the cabin with the ventilation control on "fresh?"

[SZfiftyfour]

Check the air-filter housing for oil. If you have excessive blow-by it would collect in the filter box and drip onto the exhaust. Just one possibility but its super easy to remove it and check.

[limikjr]

Heat up some oil until it smokes, take a whiff.
Heat up some antifreeze/coolant until it smokes, take a whiff.

You are training your nose to tell the difference in smell between oil smoke and antifreeze/coolant smoke.

When you determine what is causing the smoke, it narrows down where to look for the leak(s).

Definitely smells like coolant.

What is the temp gauge doing when all this is going on?

Gauge doesn't move from halfway.

Also, are you getting smells in the cabin with the ventilation control on "fresh?"

Sometimes I can smell coolant.

Check the air-filter housing for oil. If you have excessive blow-by it would collect in the filter box and drip onto the exhaust. Just one possibility but its super easy to remove it and check.

No oil




So I ran it today and it started smoking from near the top of the engine. Not a lot, just a little. Is it possible it's the head gasket causing a small leak?

[Dr_Snooz]

I would look for a leaking hose or thermostat cover before considering other more expensive alternatives.

[car6289]

I would look for a leaking hose or thermostat cover before considering other more expensive alternatives.

Get the cooling system pressure tested.
In the same area as the thermostat cover is the thermostat housing to head "D" shaped o-ring. If you haven't discovered already, most of the rubber seals on or near the engine harden with age and heat. Once hardened the seals stop sealing and start leaking.