So I swapped an 87 22RE into my 85 4runner and it runs pretty good. It sounds fine and has power, doesn't smoke or burn oil. But heres the problem.. I keep losing coolant and I can't find where. Sometimes while driving I get a whiff of coolant, usually under load.

I pulled each spark plug and looked into the cylinders with a light. The pistons aren't shiny clean or rusty. The engine isn't overheating either. Also water is not coming out of the tailpipe in vapor or liquid form.

I've looked and looked for a source but I can't pin point it. I tightened the hoses coming from the water pipes that go to the heater core. Anyone got any suggestions?

And.. The black plate on the back of the head, is that for coolant or oil or part of the EGR?

 

I have no clue. yeah that plate on the back of the head is for the EGR system.

 

Thats what I thought it was for, so it has nothing to do with coolant.

 

id say compression test time.

 

You didn't mention it, but have you checked the oil?

 

Check the obvious first.

Pin hole leak in a hose that only sprays a stream under pressure. Probably spraying on the ground and not the engine.

Run in place until the t-stat opens up and look for leaks.

 

This exact same thing happened to my '94 S10 Blazer. It was the heater core. Not too expensive to replace. When I ran my hand through the carpet on the passenger side it was loaded with water/antifreeze. Give that a shot!

 

All of the above.

 

The plate on the back of the head is a passage for the EGR but it seals the coolant jacket in the back of the head as well.

Fill the cooling system with the engine cold the put the cap on and run it in place til it warms up as waskillywabbit said and see if you can find a leak

Timing chains can wear a hole in the cover and cause a leak into the crank case and if it is only slight it can be difficult to see on the dipstick. There is also a plug in the head under the cam that can cause a slight leak.

Headgaskets can be a slight leak for quite some time. It was suggested to check the compression, but if the gasket were that bad that it would be evident in a compressiontest then you'd have some serious overheating issues. The best way to detect a slight headgasket leak is to test for the presence of CO2. The only way this by-product of combustion can get in the cooling system is through a leaky headgasket, or a cracked head or block.

 

how much coolant does it lose over what length of time?

 

Pull your dipstick and see if the oil is foamy or has bubbles.

 

I changed my radiator a couple of months ago and just now found a leak because the engine side of the main coolant hose wasn't tight enough. I noticed it was very slowly losing coolant, but I couldn't figure out why. And I was seeing residue all around the radiator.

Unfortunately I only found it because it was leaking hot coolant onto the alternator belt, which then blew up. Of course that one had to go, not the farthest one from the engine.

I tightened the clamp up real good, and hopefully it won't leak anymore.

 

Check also in the area where the thermostat housing bolts to the head; there's a sort of a deck there, behind the tstat, that has a temp sensor in it and vacuum hoses above it; My 22RE had a mystery coolant leak there; it would only come out when hot, and gradually a deposit of dried green coolant was deposited on that deck...use a good flashlight.

 

in all of my infinite wisdom(talk about a liar) i have had this same problem on different vehicles. one was a head gasket leak so fine it evaporated as it ran down the block. the second one was a small hose under the intake, and the hole was on the bottom of the hose, and the third was a radiator with a pin hole. in all situations, i found the leaks after driving around for a while, and then parking the truck, leaving the engine running and crawling under it with a spot light, tracing every hose , and looking at the head gasket front to back. you may have to rev the motor for enough pressure to create the leak. good luck.

 

If the leak is small enough and he has a fairly long commute, the coolant could steam out of the oil and it would appear to be normal. Look at the underside of your oil cap for milky stuff.
I would recomend a pressure test of the coolant system.

 

There isn't any milkshake in the oil, I've been watching that one. I'll keep driving it and see if I can't find it yet. I tightened a hose clamp after posting this and it seems like it's slowed down some but I'm not positive yet.