99 3.4l v6 (5vz-fe)

220,000 miles.

I'm getting no cabin heat. I checked the heater valve and the cable is fine, tested turning the switch from hot to cold and it pulled the cable + valve from one end to the other. No leaking from the valve, also.

3 years ago I swapped out the original radiator with this one:

Koyorad Radiators OEM Replacement Radiator Toyota Tacoma 3.6L V6 AT 01-04 | C1755

Everything was going smoothly until about a year ago when I noticed a pretty consistent drip coming off the lower radiator hose at the thermostat housing end. It also over heated once. After noticing that, I replaced the thermostat and upper/lower hoses/clamps and drained/filled/burped.

Now, about a year later, my heat isn't working. I can hear fluid rushing around the dash when driving every once in a while. I did a little research and found that it most likely means theres trapped air in the system (I know that this could also be indicative of a head gasket issue, but I doubt that's what my issue is). I have burped multiple times and I still have no heat, and still hear the rushing fluid sound. In addition to that, I have noticed coolant splatter on both ends of my upper radiator hose, as well as on the thermostat housing end of the lower radiator hose. The other day, I noticed a small drip coming from either the inlet or outlet hose(I'm not sure which is which) for the heater core (the drip is coming from the left hose in the picture). It only started dripping after I barely touched the hose on the left (pictured). In addition, my overflow tank keeps getting drained. No overheating this time, though.

It seems to me that coolant is being sucked into the cooling system, not returning to the overflow tank, causing the cooling system over-pressurize, and the excess coolant is escaping out of the hose ends. Everytime I open the radiator cap, the coolant is full, but the reservoir is empty. I was thinking that maybe my radiator cap is bad. But, why would it allow coolant to be sucked into the system, and why would it leak out of the hoses, instead of the cap if the cap were the issue? My logic might be flawed, because I'll admit I don't have a full grasp on how it all works, but thats what makes sense to me.

My first thought is that my heater core is plugged. Would that cause the system to over-pressurize? But, if it did over-pressurize, wouldn't the cap allow coolant into the overflow reservoir?

Here are some pictures:

So, from my understanding, the inlet hose should be the one connected to the heater valve, right?

If so, that means that the hose on the right, is the inlet. The hose on the left is the one thats leaking. If not enough coolant is getting through the heater core because its plugged, then why would the outlet hose be leaking?

I'll probably do a flush on the heater core with CLR. Anyone got experience doing this with the 5vz-fe? Any tips?

Attached Images

     

For some reason the top picture with the heater core hoses is upside down. FYI

If the radiator cap is not venting (pushing coolant into the reservoir as it heats up), the pressure has to go somewhere. By the looks of it, you have coolant leaking at multiple hose connections. The coolant will always leak at the path of least resistance when it is pressurized which is probably the various hose connections.

I would replace that radiator cap (OEM) and see what happens. You should also clean off the burnt crusty pink stuff on each of those hoses before starting it up with the new cap. The part is cheap and a good place to start.

Make sure you top off your coolant after you put the new cap on and clean things up. When the truck is at operating temperature, the reservoir should be right at the "Hot" mark. When it cools down, the coolant will be sucked back into the system and it will go down a couple inches (the "cool" mark).

It does sound like you may have air in the system too. I suggest getting a radiator funnel and burping system while you are topping off the fluids. Driving the front of the truck onto some ramps or a few blocks of wood can sometimes help air get out of the system while burping it.

Do these things first and see if your heat works or not. You may have two different problems but it may all be related to a bad radiator cap and air being in system.

PS. Be very careful that you do not over heat your engine. These engines do not handle being overheated very well. Hopefully you didn't do any serious damage.

Its leaking because you have installed non-OEM hoses and screw type clamps.

Yeah...I'd switch back to the OEM (or =) clamps and hoses, if possible.

Thank you for the detailed response!

So, I don't know why I haven't purchased a spill free funnel until recently. They make life SO MUCH EASIER when filling/burping. No mess, and you don't need a second person to hold the funnel while you check temp/rev engine. I purchased one a couple weeks ago when flushing my 4th gen. Should have done it sooner.

As you guessed, and confirming my suspicion, there was air trapped in the system. Quite a bit of air, I might add. I let the engine idle while up on ramps for about 30 minutes total before I felt confident all of the air was out. I revved up to 2500 rpms off and on which really helped to release the trapped air. I guess when I thought I burped it good enough before, pre spill-free funnel, I hadn't.

Anyway, heat is back full bore, and no leakage/loss of coolant so far. Its only been a day, but I feel pretty confident that was my issue.

I cleaned up all the dried coolant and any stains so I can monitor it from hear on out. Also purchased a new OEM cap from the dealership, just to be safe.

Thanks again!

I actually purchased a couple Oetiker stepless screw clamps from aircraft spruce the other day, just waiting on them to arrive. I only purchased two, because at first, I was only seeing coolant stains on the engine end of the top hose, and the thermostat housing end of the bottom hose. I figured thats where it was getting hottest, and there was a better seal needed. I'll probably end up purchasing a couple more for the radiator ends just to be safe. At the same time, if my issue was too much pressure, i'm happy it was the hose ends that gave, and not a head gasket or the radiator.

These clamps are "screw type" clamps, but they give a perfect 360 seal. They are also not likely to come loose or fail like those worm drive ones I have installed currently. You should look into them if you haven't already. Are the OEM spring type? I also worry about those failing.

OETIKER STEPLESS SCREW CLAMPS from Aircraft Spruce

I purchased item # 045-9.

A little update:

After driving it around a little more, the radiator hoses still aren't leaking. I did notice the outlet heater hose at the firewall does still have a slow drip. I am not getting as much heat as I've had in the past (but more than I was before this last burping), and not as much heat as I felt like I was getting yesterday when I had it up on ramps while burping the system. Yesterday was quite a bit hotter though, so maybe that was why.

I think I am still going to flush the heater core after the weather gets a little better.

Does anyone have a good recommendation on cleaning out the heater core? I watched a video of a dude using CLR. I'm afraid that might be corrosive. I've also read about other heater/cooling system cleaners that might be too acidic for our systems.

I was going to find where the inlet and outlet hoses routed to in the engine and pull them, so I don't have to worry about breaking/cracking any brazing or anything on the heater core. Then I would buy a fitting to connect a garden hose and back flush it without turning up the garden hose pressure too high. After that, I would reverse the flow direction again, and flush it. Repeat that a couple times, empty the water out as much as possible, then fill with coolant, and reconnect the lines. In the aforementioned video with the CLR the guy used a compressor to force out any debris in the heater. That scares me as the core is not rated for high psi.

Can you believe it was 72 yesterday here in utah, and its going to be snowing tomorrow? That was a dumb question; of course thats believable.

I don't know that that's WHY its leaking, but it probably is part of the issue, good call.

I wouldn't apply any significant pressure to the heater core. You are right, it is not designed to be under high pressure. If it ruptures, you will have to tear the entire dash apart to replace the heater core which I've read is a bigger job/PITA than an engine replacement on these trucks. Just do several series of flushes and reverse flushes to hopefully clean anything out.

I've used CLR on other vehicles before and as long as its not in there for a long period of time, I'm sure it will be fine. I've also used the "gunk" brand coolant flush stuff which seemed to work ok.

The constant velocity clamps can fail too, so can the original OEM hoses....after 20 years. I had a leak on one of the back heater hoses (the two hoses up against the firewall behind the engine) that was original with the original clamp on it. I would replace that section of heater hose that is leaking and put a new clamp on it (clean up the male connection too).

I recently had a leak develop from the heater hose that goes from the control valve to the heater core. It was the original OEM hose/clamp. I put a new hose on it and reused the clamp, zero leaks for a couple months now.

I personally haven't had any problems with standard hose clamps so I'm not opposed to using them, I've had a few on my truck for several years with no issues. Just make sure you use high quality stainless steel ones.

Based on the area you live and the quality of water, you may have calciumcarbonate (CaCO3) buildup inside the heater core. I bought a LandCruiser with the same symptoms. Little to no heat. I treated its heater core with 9% vinegar (most stores carry 5% but look for 9%) and problem solved.

Vinegar is a mild acid and reacts with CaCO3 to give off water and CO2 (carbon dioxide).

I attached two transparent hoses to both heater core lines (NOTE: if the factory hoses are hard to remove from the aluminum tubing, use a pick to break loose the rubber hose from Aluminum tubes: NEVER use a pier to twist the hose and filled with 9% vinegar and allow it to sit over night. Next day I emptied the heater core with come low pressurized compressed air. I got white loosened CaCO3 out of the heater core!! Did that few times.

CLR is OK but I wanted to go soft on the heater core: My cousin ran 100% CLR on his 2000 pathfinder and obtained good heating, but I would not recommend CLR as the first option.

I'm going to give vinegar a try. It's actually my go to for cleaning/disenfecting. I do need to get some of the stronger strength stuff though. Great advice!

I'm going to throw those stepless screw clamps on the engine end and see how they hold up, and just leave the hose clamps on the radiator end and keep an eye on it.

After driving around a little more, Im hardly getting any heat again. Opened up the hood today after about 10 minutes of driving, and the upper radiator hose at the engine end was leaking pretty bad again. Since I already replaced the cap, im hoping its just the clogged heater core.

My question is; if I do indeed have a plugged up heater core, and have the heat turned on, could that potentially be what is causing excess pressure to build up in the system? If thats the case, would leaving my heater in the off position stop the building up of excess pressure?

You said you replaced the thermostat. Was it OEM or at least have a jiggle valve?

A 100% clogged heater core is equal to heater coolant valve fully closed. I have two valves attached, one to inlet and one to outlet on my corolla and 4R heater cores and never had a leak elsewhere. Problem that you have is a leak because the hoses are little too big in diameter. If you have installed an OEM radiator hose, it takes a fair amount of work just to get it on to the radiator. Once you get it on even without the OEM clamp on, you will have hard time pulling the hose back out.
OEM hose have (I believe) yellow and while lines marked on either end). While line end goes to the radiator and yellow end goes on to the engine side.