98runners

So I have been battling my 4runner for sometime now. First I replaced the headgasket because I was burning coolant. Only to find out that the car has been overheating before the headgasket blew. So I replaced the thermostat. same problem. after the car is fully warm 3/4 to the red on the temp gauge, I grab the lower radiator hose and its cold still. I thought maybe the water pump but that was replaced about 30k ago roughly a year and a half. Also i get constant heat in the cabin. So I plug a coolant pressure tester on the rad cap and it builds up pressure. but when I give it some gas the pressure increases. is that normal?
how do I test if the water pump is still working? and is there a way to test if there is blockage in the radiator? I'm starting to run out of ideas. its a 98 manual 4runner with the 3.4

Qyota

Drain the coolant, disconnect the radiator hoses and run water through it. If the water flows nicely, the radiator is probably OK. They are cheap and easy to replace, though. If it's never been done, consider doing it. The other thing to check is your engine fan. If the clutch is worn out, it won't spin like it should, and temps will rise. Does the fan "roar" during a cold start-up, or after it's been sitting for a while after a drive? It should run for about 20-30 seconds, then go down to idle speed. You might need a new fan clutch.

And the lower radiator hose should be relatively cool, even at operating temp.

tunnelmotor99

If it has overheated before, a previous owner may have put a bunch of stop leak powder in the radiator in an attempt to stop the blown head gasket and subsequently plugged it up...I have seen it happen several times. You will get a pressure increase when you throttle up because the water pump is engine driven and pumps faster when the engine revs. I would look at replacing the radiator next as there isn't a way to look inside it without tearing it apart.

98runners

thanks for the quick replies guys, I have a complete parts car outside so I'll swap out the fan clutch and the radiator at the same time. is it possible for the stop leak to plug something in the engine or heater core? also if it is the stop leak is there a way clean that stuff out chemically? w/o ripping apart everything? I remember hearing the "roar" when I was driving it around before the cloud of smoke, but I havnt bothered to listen for it after I put everything back.

Team420

I would swap one part at a time... I know it COULD mean more work, but at least that way you'll know which part was the culprit.... I only say this cuz I have had issues before where I replaced a bunch of stuff to fix a problem, and it did fix the problem, but I now have no clue which was the culprit, which gives me no help for next time....

brian2sun

Did you resurface the heads when you did the head gasket? TThe heads may have warped when it overheated causing the new HG(s) not to seal. Did you check the heads for cracks when you had them off? The constant heat in the cabin is kinda weird. I would probably do a compression test on your cylinders and possibly a leak down test too. Look at your plugs to see if there is coolant on any of them. If the PO used stop leak, that stuff is probably all throughout the cooling system. Did you see any silicate goop when you did the thermo? It's hard to get all that crap out of there. Probably the best way would be to use water pressure to blow out the coolant passages and definitely get a new radiator if stop leak was used.

tunnelmotor99

If there's a way to clean that crap out, I've never heard of it. The stuff I'm referring to is a powder and it is notorious for clogging up radiators and heater cores. I've heard you can actually use ground black pepper and it works the same...
Are you getting full heat regardless of the temp selector position? This could be either the heater valve is stuck or one of the damper doors inside the evaporator case is broken or stuck.

98runners

I guess the heat thing was just a hot day... lol it was the only warm day of the week when I tested. I didn't have the surfaces decked by a shop but I cleaned them to a shine and made sure they were within spec before I put the heads on. I didnt see any cracks on the head. I've done a compression test and they all came out 165ish. I didn't remove the other plugs when I did the test and this was 4 strokes. I didn't use the goop for the thermostat.
I'm trying to make time to check these things out but between work, school, and being without a car kind puts a strains on things. But I had a few minutes to fire up the car and let it warm up as like before I let it get up to about 3/4 before I shut it off and felt the upper hose and it was hot. lower was still cold so I felt the fins and only the very top of the fins were warm the rest were all cold. How can you tell if a water pump has gone bad?

98runners

here is a video of the start up. I didnt hear the roar that you guys are talking about.
http://www.youtube.com/watch?v=tkIyQ3vBlfs
(its a crappy phone video)

bicklebok

Did you ever get it figured out?

98runners

I'm leaning towards the radiator but I dont have the time right now to swap it out. I probably wont have a chance until after this term is over. I spoke with a buddy of mine who had the same problem, he did the water pump and the thermostat only to find out it was a clogged radiator.

If it's not the radiator I'm just going to swap out the motor with my parts car. I have a week off before my summer term starts. Is there anything I should need to know before I completely pull out the motor?

bicklebok

As mentioned already, take the lower hose off and see if water runs through it smoothly. I test radiators for blockage by letting the engine warm up then shut it off. Take your hand and feel different spots on the radiator for "cold spots." That will let you know if there is blockage.

Have you tried running it a few minutes without the thermostat to rule it out? If it doesnt run hot with the thermo out, it's the thermostat. Just trying to give you simple things to rule out the easy stuff first.

SOmetimes it can be a combination of things, which makes it even harder. I ended up replacing my radiator and fan clutch before I solved my overheating problem.

98runners

Okay I finally got time to work on the runner today and ran water through the radiator and it went threw fine. I boiled the thermostat and it opened up fine as well. Now I'm wondering what are the symtoms of having the headgaskets on wrong? also I did a coolant pressure test and after 20 mins it did lose .5 psi. (I'm not sure of this is a due to it being a harbor freight product or what). I'm thinking about just pulling the motor but one of the y-pipe bolts that connect to the cat is stripped. Is there anyway to get the trans off w/o pullning the y-pipe? Is there a way check if the HG is on right? I'm starting to run out of ideas

toyotacharles

is the truck still cabable of starting? what does the clutch fan feel like really easy to turn or hard to turn and stops quickly?

calvinh

I had very irregular overheating in mine for a year. Wouldn't do it consistently until about a month ago. The first time it started I was on my way out of town and instead of risking it I took my friends truck. He changed my thermostat for me while I was gone with a Stant brand. It still overheated on occasion but always different driving conditions. This last time it did it I pulled the radiator and ran water through it and it didn't seem restricted except compared with the new one which definitely had more flow. I also swapped the T stat for a Toyota brand which definitely opens wider than the Auto Zone one did. This seemed to fix the problem but I did go ahead and change the fan clutch for good measure. So far no issues, knock on wood. And we've been having 106 degree temps and my AC on full blast and my gauge hasn't even reached mid point.

98runners

The car is able to start but the starter just completely failed a couple weeks ago. I put a clutch fan from the parts car and it spins with very light pressure.

toyotacharles

it should be stiff to turn almost stop as soon as you let go of it

98runners

that pretty much describes it.

TheDurk

The best indicator of a fan clutch's health is the roar on cold start-up, IMHO. Last summer I had my 11-year old bad one and a good new AISIN right out of the box side-by-side. Just playing with them cold I could find no difference in spin resistance. Both were pretty much as described above. The magazine test is hit-or-miss, as things have to be really hot for the clutch to engage 100% of the time. The good one failed some of the time; the bad one failed ALL the time. The one thing that was completely absent from the bad one and present on the good one was the roar on cold start-up.

98runners

well the starter is completely dead so I think I'm just going to bite the bullet swap the motor with the parts car. I might have another use for the engine anyways. because I had a few friends come over to help with the diag with no luck. any helpful tips for removing and installing the 3.4?