gen 2 4runner questions re coolant system

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semlin

semlin

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hi i just helped my brother in law buy a 1990 4runner V6. needs a little coolant attention.

didn't notice until after we bought it that the heater does not blow very hot. temp gauge also does not get all the way to half way.

it has a rear heater that blows hotter but still not really hot.
the heater control valve operated by the cable seems to work fine. no sign of coolant leaks. no bubbles in the overflow.

I am thinking stuck thermostat and/or possibly blocked coolant as the po just recently had it flushed and it was switched to green from red coolant.

any other thoughts? might i be missing anything?

Also, where is the block drain plug on this model?
 
OH... where to begin, ... NO Tstat...
ONE, "heater not getting hot and the gauge not going up are not charictoristic of over heating hance "no sighn of coolant leaks" "no bubbles" etc.

TWO, A clogged or block drain, does.
Three, TMK & IMHO, DO NOT USE RED COOLENT!!!!!!

Four, don't worry with the block drain plug you dont need it. AKA, You can do what you need without it *IF*, done properly. AND I dont think you can reach it(or want to try)

Five, high coolent flow(unobstructed) means it wont get hot

Six, Fix it or it will get horrable gas mileage.

Seven, fix those muffler bearings while your at it.
IH8W8
 
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um, thanks

so i didn't actually understand most of that. i get that you don't think it is the t-stat and don't like red coolant. i get that you don't think a blown head gasket could cause a heater to blow cold, and i get that you think I can flush the block out properly without popping the block drain plug if i use some unspecified procedure.

what else?
 
OH, WHERE to begin.
Allow me to reiterate, re-read #Five, then ONLY the top line.

ONE, there is no T bettwen "NO" & "Tstat" implyes sentence frag.

TWO, youre heads would have to be pouring in order to be a "Blown HG"(u'd no then) and low heater temp.

THREE, heater would blow cold if there wasen't ANY coolent

FOUR, My Toyota book specifys checking the nut behind the wheel FIRST before attemting any other procedgers. (just kidding)

Seriously, my comments are desighed to get you thinking before you waste a bunch of time, both yourself and some one elses trying to diagnoce a problem. I'm not a jerk I just play one on TV.

PS The "specified procedure" is :censor: due to liabuility reasons for my protection check out other threads for the answer.
IH8W8
 
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uh ok
i've already been thinking thanks. I think either the tstat is stuck open or its blocked. either way its going to get flushed and a new t-stat. i guess it could be there is no t-stat as well.
 
I would check the T-stat first, if it's stuck open or not there that would explain the issues.

There are 3 drains on the 3VZE one on the radiator, which as tntoyota said will get most of the jobs done, just open it up and open the rad cap. It should have a little hose going down through a hole in the brush guard to make it really easy. You may, once drained, want to get a new o-ring for that one, I fought with mine for a long time till I got a new o-ring.

The other two are on either side of the block, it's hard to tell in my FSM but the pass side looks a little higher and forward of the one on the drivers side. They may be very easy to get to from the wheel wells, but I never needed them.

If you are going to drain the coolant to check the t-stat, you may want to back flush the heater core, if it was flushed the same way coolant always flows, it would not flush out the debris..... Just thinking out loud.

tntoyota, I know you're trying to help, but you have to hit the enter button sometimes man. It makes it hard to get the info you're trying to give when it's all jumbled together. :D Just trying to help you help others. :cheers:
 
t stat and a acid flush is in order.
and it is possible there is a kinked hose. just a thot. :D

recently i discovered a new teqnique. unfortunatly it requires the help of a shop.

this tool i discovered is a coolant vacuum holder. basically it applies and holds vacuum to the coolant system, pulling out the air, and at the same time time checks for leaks.

i really am not sure what the name is of this tool is, but the one i saw is from Matco Tools.

i like Jerods ideas too. a reverse flush would be a good idea
 
tntoyota please dont take this the wrong way but do us a favor and just write everything out and drop the abriveations for a bit its really hard to decipher your posts. (unless its on purpose and your just trying to get me to scratch my head then by all means disregard this post) :D
 
I am actually having the exact same problem, so far no one has been able to tell me what is wrong with it. I have a 95 4runner with the 3vze. The t-stat has been replaced twice in the last 2 weeks. I bought it last Monday. I figured the lack of heat was maybe due to a mis-installed t-stat. So I then replaced it again. The thermostat is not the problem, well, unless I got two new bad ones in a row. The upper radiator hose is very hot, and the lower one is quite cold. Has anyone else figured out what's going on with this yet?
 
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tntoyota said:
Three, TMK & IMHO, DO NOT USE RED COOLENT!!!!!!
Click to expand...

What in the HELL would ever possess you to post such drivel?

Toyota OEM coolant for these engines is red. This is what is supposed to be in it, not that green Prestone crap. My '87 has had red in it since day one, and the coolant passages are still perfectly clean, I'm still on my original radiator, 213K miles.

GAAAAD I *hate* it when people post incorrect info on these forums, thinking they know what they're talking about, but they base all their knowledge on rumors.

Anyway, I have had a lot of trouble getting these engines properly de-aired after draining the coolant. A lot of it is due to the t-stat being low on the engine, connected to the bottom hose instead of the top hose. The engine will get very hot, but the temp gauge will read low because there is no coolant in the passage where the sensor is, so it can't get a proper reading.

What I always do when re-filling is first fill the radiator till it's full, then I disconnect the top hose and back-fill the engine from there. Then I park it on stands/ramps or nose-up so the rad cap is nice and high and the air bubbles out here when I first start it up, making sure all the heater valves are totally open too.

I also think your heater core(s) may be clogged with corrosion, consider an acid flush.
 
sorry, i thought i updated on this. acide and a back flush did the trick but even then it did not kick in until a couple of hours of driving at which point it needed a small top up. I'm sure that was trapped air.

and i told my b-i-l to stick with green coolant but only because he is likely to forget not to mix down the road or take it somewhere too clueless to not mix.
 
semlin said:
and i told my b-i-l to stick with green coolant but only because he is likely to forget not to mix down the road or take it somewhere too clueless to not mix.
Click to expand...

Well, then tell him to start saving up for a HG replacement. Many of the failures I have seen have been due to erosion of the gasket from the wrong coolant.

I see people saying all the time that you can't mix the green and the red, but I have yet to see proof that you can't do this. I tried it once in a jar, it just made a funny color from the green/red mix, but other than that it looked and smelled OK to me. I wouldn't do it as a habit, but if the engine has red in it now and you need to add some, a little bit of green in there won't hurt a thing.
 
KLF said:
Well, then tell him to start saving up for a HG replacement. Many of the failures I have seen have been due to erosion of the gasket from the wrong coolant.

I see people saying all the time that you can't mix the green and the red, but I have yet to see proof that you can't do this. I tried it once in a jar, it just made a funny color from the green/red mix, but other than that it looked and smelled OK to me. I wouldn't do it as a habit, but if the engine has red in it now and you need to add some, a little bit of green in there won't hurt a thing.
Click to expand...

Dunno about the trucks, but it is pretty well documented in the 80 section that when you mix the two and add heat and pressure, over time the mix makes sludge....
 
klf if you are saying green coolant eats toyota head gaskets i'd like to see some data to back that up. 80s have their share of h/g issues and green coolant is not an indicator.
 
You're correct, I don't have any proof, other than what I have seen on several HG repairs. The guy that I bought my '87 from was a tech at a dealership, he used to do HG jobs all the time, and he noticed a very strong connection between corroded gaskets and green coolant in the engines.

I believe the 80-series HG failure is more linked to a faulty gasket design, much like the high failure rate in the 3VZ-E V6 engine.
 
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