infinityisfive

Hey all good day (or night), and before you ask, I've been searching all over. Maybe I'm doin it wrong but I can't find exactly what I'm looking for so far so here goes:

'89 Pickup DLX 3.0 stock 180k mi, build date Nov. 1988
EDIT: using red toyota coolant specified for the truck

To any of you who are experiencing heater related woes: I replaced the heater control valve located at the firewall, in the engine compartment, at approx 150k miles with the same model plastic one from the web (around $46). It was leaking from the screw at the bottom of the plastic housing. The new one came with no seal or gasket around this screw, which I thought was weird, but there was none there to begin with so I went with it. Well, the replacement still leaked so I ran the truck with no heater for about a year. Now I'm diving back into it.

Now the leakage is coming from the hose AFTER the valve, in terms of water flow (so facing the engine bay at the front of the car, it's the hose on the left of the valve, after water passes thru the valve, flowing into the heater core) ALSO the heater return hose also leaks right at the joint into (coming out of) the firewall, which causes a drip onto the exhaust crossover pipe and makes a scarily unnerving noise. I -think- this is because I ever so slightly bent the pipe upon install of a new hose, but it looked too miniscule to be the cause of a problem, especially with the hose pushed on all the way back, into the rubber surround. I could be wrong and will be addressing this.

I've tightened the first hose mentioned above after noticing it being loose, and plan on attacking the second tomorrow morning.

The drip from the first hose also caused the heater control cable to get stuck, leaving the valve constantly open. What I'm wondering is with hot coolant always in the heater core, and with the truck running slightly low on coolant from time to time, plus me not having burped the water system leaving air in the system (which expands faster than water), could the heater core create a pressure situation resulting in hot expanding coolant leaking out from the return hoses, and be the root of the problem?

If so it sounds like there's a blockage issue where the heater return hose flows back into the engine and might suggest the thermostat not opening correctly. This is after the car's warmed up so who knows. I've noticed there are multiple coolant setups and I've seen a few schematics so I really have no idea how mine should be and am winging this until I find out more about it.

Tomorrow will be spent putting the dash back together and ripping those hoses back off to see what's up, if they're clear and devoid of blockage and how much of that return pipe I need to bend back into shape.

Possible solutions:
-Straighten return pipe at firewall
-Burp the system
-New radiator cap
-Replace thermostat to improve circulation (right now I'm running the two-stage model but I don't believe it's a Toyota brand, replacement was done around 150k miles, a few years ago)
-Eliminate heater control valve altogether


The truck doesn't overheat, has no other leaks that I've noticed and has been pretty good with the exception of scaring the crap out of me every time I hear that stupid crossover pipe being way too hot. I've replaced every coolant hose except for those tiny ones that are hard to get to.

Now, other cars have been designed to always allow coolant into the heater core, but for some reason or another, these Toyotas haven't. This could be due to a number of reasons, ranging from brand tradition to circulation efficiency. What I'm wondering is IF the heater valve is a continuing issue (assuming no part of fixing this issue works), would running a straight pipe instead of the valve create any kind of pressure situation like the one mentioned above? The valve keeps coolant out of the cab, which helps with A/C efficiency in the summer, but are there other reasons for this design? I don't want to buy a new one but if I do I'll make a little gasket for the screw.

I've noticed a few people on here running with no heater valve control, and obviously I would be concerned about changing from the stock design and I appreciate whatever thought the designers put in to the truck, but, with anything, there might be a better way about it so any input would be welcomed.


Also, unrelated, has anyone noticed the HVAC blower RPM speed control under the dash glove box? Why is that there if it's hidden? My guess is to provide a small boost in the event of a failing blower but I would venture to say that Toyota would rather just replace the part sooner when its more readily available. There's no indicator on the dial so I left it alone but still - why is it there?

Hope this sheds light on some of what is going on. I'll update tomorrow with pics of what the dash looks like when its not on the car, and anything else found that's cool. Thanks in advance guys.

infinityisfive

The circulation/outside air control was also broken so I replaced the heater control unit and ran the cables. Everything works as it should, I could have aligned the levers better today but now that I know where everything is, the dash won't need to be pulled in the future.

One thing: now the backlight for the heater doesn't work. I tried two different bulbs, plugged in the old fan speed harness and new. Nothing. I haven't tested the socket or bulbs with the multimeter yet but have identified the wires and will be hunting for shorts if the multimeter turns up negative.

No pics yet, gotta find my camera cable. Turns out the camera DOES have on board memory.

Read the thread about glove box lights on these trucks and picked up one from a 4Runner at pick n pull today and now I'm looking for an ash try light and ignition sentient circle illumination. Also plugged in a new blower resistor, now the fan works on all speeds!

The heater valve is still leaking, haven't run the truck long enough to see if the return hose leaks. I will spray the cable with some sort of lubricant to keep coolant from drying on the cable. Tomorrow!

infinityisfive

The internal contacts in the heater control display bulb bust have separated. A replacement at the store was the cure. I'm going to go ahead and order another heater valve. Found one on the web, just the plastic, no brackets, for $12. Figure if nothing else I'll make some sort of drain system to keep coolant off the cylinder head. Maybe do this for the return hose if necessary.

infinityisfive

Yeah bending that pipe is hard, I'll be researching ways to bend pipes in short/awkward situations. I'll also throw in a new thermostat and change the coolant to make sure all around that it's Toyota brand and because I noticed a darker leak than I was hoping for.

Accidentally wired the glove box light to the 12V DC cigarette lighter power line

Thought about running the lines w/o the coolant valve, but decided to just wait on the new valve. Two day shipping was only 2 dineros more than ground. And I didn't have the right length hose lying around.

Still haven't found my camera box and the proprietary cables that go with it. I bought an Olympus camera, which has 5X optical zoom and an XD to micro SD card adapter (GOLD), but has a weird USB that is weird because it can also plug into a TV. So on the memory card, I have pics of the rear differential extention breather mod if anyone wants to see the cool little filter or the way I tapped into the other taillight for brighter reverse lights.. standard stuff though. Oh yeah and the front diff breather is on the very front, top side of the diff, pointing up. Noticed one today at the junk yard. Anyone need front 4.88 gears? There's at least two 4runners with the G144 setup there. And ONE G254! but no rear diff!!

infinityisfive

Update: got the heater valve in, seems to be working - but! After replacing the thermostat with OEM straight from the Toyota dealership (old model turned out to be single stage type, which is odd seeing as how with the exception of this coolant leak, the truck's ran peaches) and the rad cap, the radiator itself began showing a few pinhole leaks at the top. The drain valve was also leaking and discoloration on the metal plate thing there with 4 bolts that covers the front diff (wtf is that called?) showed that the drain valve may have been leaking for some time.

Before discovering this I ran the truck and watched the temp gauge rise to the right level, go past it to another (mildly acceptable level), and go right up past halfway. Had the heater on HOT the whole time, never got hot, fans blowing, valve open and all. Upper rad hose was hotter than the radiator, heater send and other hoses were lukewarm (probably just from engine heat), but the lower rad send hose was straight up COLD. I noticed mud in the lower hose when changing the stat. I'm thinking this difference in pressure has caused pinhole leaks to show up and the drain hose to leak more profusely, which tells me I should swap out the original with an all aluminum 3 core and see where that gets me.

The water pump was replaced some 7k miles ago. I pulled the plugs, #6 first, which looked great. No signs of head gasket failure. Also cleaned the K&M filter (hate that thing, going to bypass it with a Mopar 440 ram air type setup, stock filter right under the scoop ).

Here's to a new rad!

bmcghie

Your description of symptoms before you noticed the pinhole leaks points towards a thermostat not fully opening... except for not overheating. very odd.

I also have a lukewarm heater, and the exact same leak pattern you describe. The air pressure bubble is an interesting idea. I'm going to find a really steep slope to nose my truck onto, and run it with the rad cap off for a bit and see what comes out.

Best of luck with your cooling system!

infinityisfive

Thanks dude! The truck's running great now with no t-stat, just a little cold and the heater isn't hot yet. I bought a 03079 OEM Toyota t-stat which was promptly defective so I'm gonna try another one of the same model and see what's up. Oh and I was able to shut the engine off before it got to overheating but the gauge itself was glaring at me

infinityisfive

What's weird is while the heater was leaking and after the valve control cable was replaced, it blew hot air like it should. On your end it sounds like there's some kind of blockage in the line but where? Does your temp gauge normally read about 1/4 the way up?

bmcghie

No, my gauge reads right in the middle. I can just see half of the symbol peeking out on the right side of the needle. The truck has a genuine Kuzeh thermostat in it, and is certainly at the proper temp.

Towing some guys out of a bit of sand in Cali on a road trip on a VERY hot day had my temp creep up a bit after 10 mins of 4low and lots of grunting... but other than that, it's never gone past halfway. It also always gets to halfway in very cold. I <3 my truck. Desert to frigid winter... no problem.

My heater seems to have improved function (blows hotter) after bleeding the system properly this last week. Haven't had the opportunity to test in freezing temps yet but so far results are good. I think the first time I swapped the coolant I did not do the best job bleeding. Air trapped somewhere near the heater core for ~2 years methinks. :s

Oh, and you were referring to the "skid plate" earlier, when you wondered about the 4-bolt-supported metal sheet. It's supposed to hit rocks, deform, and take some weight and allow the truck to keep moving over the obstacle without hitting something important (like the oil pan!)

infinityisfive

Oh yeah, skid plate, duh!

That's surprising though, my temp gauge always reads about 1/4-1/3 the way up, with the needle being parallel with the C line. It runs slightly hotter with less coolant but still at an established, consistent level that I've seen before and am familiar with. I never burped the system either but I will when the new t-stat is in. Glad yours is blowing hotter!

ansontn

Just wondering when you replace your heater control valve is the dripping or leak from the bottom of the screw like stops? That drips down the exhaust and creates sizzling sounds and smokes after you shutdown the engine?

infinityisfive

on mine it looked like it was dripping from the screw BUT it was also leaking from the hose to the left of the valve (looking at the engine bay straight on), then dripping to the screw. So it was hard to tell if there was one leak or two, if the screw actually was leaking. What I did: when the replacement's replacement came in the mail I was just super careful to not tighten the screw more than was absolutely necessary to get a good fit.

Turns out the radiator was clogged AND leaking, plus a freeze plug had started to degrade, t-stat wouldn't open, all contributing to the lack of proper pressure in the water system. The original heater valve was probably fine tbh