Missing Coolant, No Leaks

[clunker]

My apologies if I repeat information some of you have read on another post. This situation is different and it warranted a new post.

3VZE is losing coolant, but I cannot find any leaks. Idles smooth at all temps, but has high cold idle at 1500 RPM that takes forever to drop and never falls below 1100 RPM. Temp gauge never reaches full temp, and heater blows cooler than normal. Thermostat was replaced less than 6 months ago. No signs of head gasket failure. Oil looks good, oil cap is clean, radiator cap is clean, coolant looks good.

The Previous owner told me that the engine overheated, and I saw signs of this when I had it torn apart. Split loom and other plastic parts were brittle and just crumbled in your hand. Valve cover gaskets were hard as a rock. Upper plenum gasket was brittle and cracked. PCV was toast, and the grommet was broken in pieces (luckily did not fall into valves). Based on this info, I'm thinking that the lower intake gaskets might have failed just like the upper gaskets. This would explain the loss of coolant. Before I lose another weekend tearing the engine apart, does anyone have any other suggestions?

 

[Bad_Vision]

Pressure test will determine if it's a head gasket or system leak. If the engine overheated then you have a possible warped head.

You must pressure test to determine if it's loosing pressure via a leak or burning it off.

 

[KidVermicious]

My apologies if I repeat information some of you have read on another post. This situation is different and it warranted a new post.

3VZE is losing coolant, but I cannot find any leaks. Idles smooth at all temps, but has high cold idle at 1500 RPM that takes forever to drop and never falls below 1100 RPM. Temp gauge never reaches full temp, and heater blows cooler than normal. Thermostat was replaced less than 6 months ago. No signs of head gasket failure. Oil looks good, oil cap is clean, radiator cap is clean, coolant looks good.

The Previous owner told me that the engine overheated, and I saw signs of this when I had it torn apart. Split loom and other plastic parts were brittle and just crumbled in your hand. Valve cover gaskets were hard as a rock. Upper plenum gasket was brittle and cracked. PCV was toast, and the grommet was broken in pieces (luckily did not fall into valves). Based on this info, I'm thinking that the lower intake gaskets might have failed just like the upper gaskets. This would explain the loss of coolant. Before I lose another weekend tearing the engine apart, does anyone have any other suggestions?

Heater blowing cold could indicate air in the lines, which might be good news. Do a block test to rule out a blown head gasket, then go after that lower intake plenum.

 

[RAD4Runner]

I hope it's nothing major, but IF bad HG is causing radiator to pressurize, hot coolant could come out of the overflow tank and evaporate while you're driving so leaving little sign. It's happened to mine. Di you look closely around the overflow tank for signs of coolant coming out?

 

[wcjeep]

There is special dye for coolant system check. Can you rent a radiator coolant pressure kit from Autozone? Might help narrow down a head gasket, freeze plug, crack or bad radiator. Not all cooling system leaks leave drops on the driveway.

We Lemon Law'd a 2014 Jeep Cherokee that also had an intermittent cooling system leak. It would leak as a vapor only. No drips.

 

[Ahlem]

Harbor Freight has a pretty decent cooling system pressure testing kit for about $80 depending on what coupon you have or whether it's on sale. I've saved lots of time diagnosing several times by having one.

 

[clunker]

Thanks for the input everyone. Air in the lines was responsible for the lack of heat. I'm pretty sure there is a leak somewhere, but it doesn't ever drip. I can smell it at times (usually when I first start it up when the engine is already warm), but the fluid level doesn't drop very quickly. Looks like I need to do a bit more poking around.

 

[Bad_Vision]

Again pressure test will tell you all you need to know. It will force client out the leak and if it's not a hose then you will smell it like crazy in the exhaust on start up after the pressure test. Simple solution no screwing around banging your head trying to poke around.

 

[89FourRunner]

Under the intake manifold and towards the firewall in the middle is a series of tiny coolant hoses on top of the block - on my v6 one of them was leaking and drying up causing me to get a whiff of coolant now and then.

I drove it like this for three years without an issue. If you dont mind taking the manifold off - there is a chance.