Mysterious coolant leak…head gasket?

I’ve slowly been loosing coolant for a little while now. The level in the radiator has never dropped much, but the overflow reservoir was staying empty. I put some dye in the system to see if I could pinpoint the leak. Never could find anything until today. When I stopped to fill up with gas, I could see it leaking onto the ground. Upon further inspection, it looks like it’s coming from the front side of the motor, almost dead center with the crank. It looks like it’s coming from just above the oil pan, which doesn’t make a lot of sense to me.

Also, after letting it run up to operating temp so I could see it leaking, I let it cool to check the coolant level. Once I cranked it again, it almost immediately threw a P0304 CEL and running terrible, which doesn’t give me much hope. I have a feeling something with the head gasket has gone wrong

 

Is this a 3.4 V6 or 2.7 I4?

The water pump is in the timing cover either way, which is behind the crank pulley. That actually makes a sense for a leak to be in that area.

What does your oil look like? Any hint of coolant in the oil or vice versa with oil in the coolant?

I'd be prepared to to put a water pump in it since you need to tear it apart to reseal it regardless. And since you're in there most folks do a timing belt\chain (depending on if it's the V6 or I4) and the oil pump all at the same time. At a bare minimum you need to tear it down to where it's leaking and look for worn seals\gaskets, you could have a worn timing cover (fairly common in the 4cyls with a chain when the tensioner\guides get worn out or broken).

 

Does the misfire clear up after a few seconds or is it always present now? If it's always present then it's not likely related to a head gasket issue. I second the observation that it could be a failing water pump and hopefully the misfire appearing now is just a coincidence. You could do a chemical block test (rent at your autoparts store) to rule out a head gasket issue.

 

it’s the 3.4. Oil appears to be fine on the stick. It was changed not long ago so the oil is still a nice golden brown, it’s not milky in color. The coolant doesn’t appear to have any oil in it either. I didn’t think about the pump being behind the timing cover..should have thought that through a little more.

I didn’t drive the truck very long, just long enough to move it 50 yards back to the carport. In that short time, the misfire did not clear up and it was very obvious something was wrong because it was running terrible. I’ll look into the chemical block test just for piece of mind!

 

Looks like quite a leak, maybe the timing belt is spraying coolant on the sensor on the left bank cam?

I just did my water pump and timing belt last month. Found 2 good YouTube videos, Timmy the tool man or something like that was good but his way or putting the timing belt on is not as good as the other video. The easy way is to install the upper idler last after the belt is in place correctly everywhere else. Line up the cam and crank marks correctly and install the belt on the cams using bulldog clips to keep them in place while you do the rest. Search here and find the complete eBay kit with Aisin water pump and timing belt, it’s a good deal and has all good stuff.
I’d take the timing belt cover off and see if the leak is the water pump, it likely is. Oil in the coolant is not necessarily going to also include an external leak?

 

I also replaced the ac compressor idler, it was toast. Look up my recent post for advice on removing the crank pulley bolt and retorquing it.

 

I would bet that your leak is at th water pump. Those water pumps have a weep hole that is designed to leak out a bit past the seal to let you know that the water pump bearing is going to fail.

 

I didn't take everything completely apart today, but I pulled back the timing cover to try and get a better look. Couldn't really tell much from the top, there was a little dye splattered but I could not see the definite leak. It has to be the water pump. It's an oreillys water pump that about 4 years old.

On the plus side, I cleared up the misfire. Swapped the plug wire out with some old ones I had as spares, and it cleared right up. Napa plug wires apparently don't last on Toyotas. Second set of Napa wires in two years that have cause misfire codes.

 

That's the area that gets wet when the water pump is leaking

Hang a inspection mirror down by the thermostat housing and look up and to the left