sporadic overheating?

[SethM]

Help. I have the afternoon to attempt to solve the sporadic overheating my daughter is experiencing with her 1985 T4WD (yes, I own one too... apparently we are starting a family collection...). She was driving the car from CA to the east coast when she started noticing the never-moving temp gauge start to climb on a few occasions. She had one boil over but still stayed out of the red-zone on the gauge. The rest of the trip was fine but now on certain times/days she says it starts to get hot and there is coolant in that little metal lip at the top of the radiator. My thoughts about the possibilities (without further investigation) are:

bad thermostat
failing water pump
bad fan relay (last night she reported the temp going back down when she got to the freeway and was able to speed up)
bad cap (?)

Supposedly, the previous owner had a new radiator installed but I''m not sure about this and it isn't obvious if it is a new/replacement.

So far, there is no "milkshake" in the oil or on the oil cap at the top of the valve cover.

Thoughts/suggestions? What would cause leaking right at the top of the radiator?

I have changed all of the above on my car while putting it back together but am wondering if I can change the water pump (easily) with the radiator still in the car?

Thanks in advance,

[xirdneh]

I start with the cheap stuff
cap first
then thermostat
i have had problems with both on several Tercels
usually the waterpump starts dripping out the weep hole when it begins to go bad
Non of the 11 tercels i have played with ever had a waterpump that caused the over heating
a slowly or occaisionally leaking headgasket has been the culprit several times
also check your radiator. is it single or double row. in hot climes the double row works better and is the stock radiator for the 4wd wagons

[SethM]

Xirdneh,

Thanks. Was going to start just as you suggested (t-stat and cap). We'll see. I unplugged the fan sensor (learned on my car that the failure mode is the fan runs all the time) and the fan in front of the radiator came on with the ignition key but the fan to the side of the radiator did not. Have to check on my car and see if this is standard procedure.

I'm hoping it isn't the head gasket. Haven't seen signs of water and oil mixing. Is the cure for a "slowly leaking head gasket" replacement?

Will check on the number of rows in the radiator (assuming I can see these with the cap removed.... (not in front of the car right now))

Thanks

[xirdneh]

you can see the rows on the side of the radiator
single | |
double | | | has a center divider

head gasket leak can be difficult to nail down
compression test will not always catch it
slow loss of water is not for sure because it may be leaking at a non head gasket or something
white smoke out of the exhaust still coming out after engine warms up but that does not always happen
one spark plug is real clean compared to the rest

[Petros]

I concur, most likely a faulty T-stat or cap. Bad water pump will not cause overheat without leaking, it usualy just leaks coolant and you know it is bad. Check for leaks on all hoses, and possible heater core (stop leak will work on the core). Plugged up rad could cause that behavior as well, you know if turning on the heater brings temp down right away, means rad has limited cooling capacity. This can happen on a fairly new radiator if tap water was used in it, causes scale inside, limits cooling capacity. Always used distilled water in the rad with anti-freeze, it is less expensive than replacing the radiator.

Replacing the head gasket is not too bad a job, but even if leaking a little it will not prevent you from driving it. I drove mine for almost a year with a leaking head gasket, I just kept topping up the coolant every gas stop. As long as coolant is in the system it should cool unless t-stat, rad or cap is bad.

Also, make sure all the air is out of the system when you top it up with coolant. I have filled the block from the top rad hose (disconnected from the radiator), and then connect it and fill the rest of the way from the filler cap.

Good luck

[arbskynxnex]

I hate to ask the obvious first question: "Was she really leaning on it going over Mountain passes/steep grades when it happened?"

Also check the belt.

[SethM]

OK, THANKS to all who have replied so far. As I said, this is my daughter's car (funny story how she ended up with it but that is for another thread..) and she is using it as a daily driver to get to her summer job. I had hoped to fix it this afternoon (supposed to be going out of town tomorrow).... Here is what I did, found out today:

[Oh wait, first-- no, I don't think she stood on it over any mountain passes. She's pretty conservative in her driving and knows the limitations of the T4WD AND she was watching the gauge pretty closely the whole way x-country)

Now today:

1) I pulled the connector on the fan relay at the bottom of the radiator
2) turned the ignition switch on and the fan came on. So--- the fan motor is fine (see below for my "new" concern for the fan switch/relay itself)

3) Installed a new thermostat
4) installed a new radiator cap

Daughter takes car for a test drive, starting from a cold motor (but it was a warm day here (70s). She gets less than a mile and calls to say the gauge was climbing so she pulled over and saw coolant leaking/spraying.

She drives back to the garage and I find that the leakage is from the gasket area of the new thermostat. Damn! that is a tricky think to hold the gasket and the t-stat in the right place in the housing while horizontal!! I did this with no problems on my T4WD about a year ago but can't remember if I had learned any special tricks from all of you here.

So, that is one "fix" I have to repeat BUT

The radiator was hot (indicating to me that the t-stat had opened and coolant was circulating) as was the block AND yet the fan had not come on. Given that the gauge was at the 3/4 level (as opposed to its usual 1/2 reading), I am assuming that the fan should have come on. Do you just change the relay/switch at the bottom of the radiator?

Speaking of the radiator--- I learned today that both my car and my daughters have the "single row" of fins..... Both were replaced by previous owners. Are the double-row radiators still available as aftermarket items?

So that's it--- looking for tips on how to set the t-stat and gasket right this time and tips/comments on the fan switch/relay. I could pull the relay off mine (currently in storage) and swap it onto hers tomorrow morning (assuming this isn't something readily available at NAPA).

Thanks,

[Petros]

I had the same problem with the gasket on my t-stat housing, I used Permatex gasket sealer on it to hold it and the T-stat in place, helped a little.

The single row radiator will work fine, I have driven one in hot desert temps on a loaded T4wd without issues. There is just not as much excess cooling capacity as the double row. They are interchangeable and many parts houses list the same rad for both the 2wd and 4wd as the same, but the 4wd wagon was supposed to come with the double row rad. I bought one new from an aftermarket supplier a few years ago, it should still be available. The single row radiator is not your problem if it is internally clean and working properly. If you need a new radiator, than by all means get the double row one as a replacement, but I would not replace it if it is in good condition.

Swapping the fan switch is a good and easy test, they do go bad. Usually they fail in the "on" position, but it is possible to fail either way. Realize that if you are moving faster than about 35 mph, the fan adds nothing to the cooling since air will not flow through the rad any faster than that speed anyway. So if it is overheating at hwy speeds, it is not the fan switch that is causing it. Driving slow in heavy traffic, or slow on hot days, the fan will need to function properly. And if the overheating is indeed "intermittent" that could be your problem. Gets hot when driving slow, cools down when speed picks up perhaps? You need to quiz your daughter (or test drive it yourself) to find out when it does get hot and when it does not if you want a more accurate diagnosis. Also, if the fan switch is bad, another simple test is to turn on the heater fan (in full "heat" position) it should bring the temp down fast.

Good luck.

[SethM]

Petros- on the behavior that would be consistent with a bad fan switch- Yes, she was paying attention and reported that indeed the temps started to come DOWN at higher/freeway speeds (see my first post).... as you suggested this seemed to me to indicate overheating when the fan is counted on to prevent it and no overheating when pure speed is moving air across the radiator. Will pull/replace the switch tomorrow. Thanks for the Permatex suggestion.

[SethM]

Thanks again to all who posted suggestions.... Today I installed a new radiator and all is well... Last Friday, after changing out the t-stat and fan switch, I noticed a leak at the top seam of the radiator. The new radiator was available in one day and a snap to install and now everything seems fine. It DOES have a plastic (??) top but we'll just cross our fingers.

One final question for the experts here: How do I tell if the fan switch is working? I am assuming that when I discconnect the connector and the fan reverts to always on, that that result tells me the fan motor is working (and perhaps that the wiring to the fan is fine). But how do I tell if the switch is switching on as designed? Today, I ran the car till it reached operating temp and we took it on a fairly long test drive in rather hot ambient weather. Up some grades. The temp gauge on the dash never climbed above the mid-point and no leaks in sight. BUT, the fan never came on either. When SHOULD the fan come on?

Thanks. This list is what allows me to keep TWO 1985 T4WDs running (including one serving as the daily driver for my 22 year-old daughter).

[Petros]

The plastic header tanks on the rad are normal "stock" OEM radiators, some aftermarket suppliers have it in all metal. should last 15 plus years.

To test your fan switch just let it idle, when fully warm while sitting in your driveway. Watch the temp gauge, typically it will get a bit above half way and it kicks on (you can hear it), and the temp drops to below half way and the fan shuts off. Keep your eye on that temp gauge, just in case the switch if bad, turn on the heater with fan on high to bring it down quickly.

[SethM]

Thanks Petros. Will try that little test when next I see the car. She is happily driving it to/from her summer job now. And keeping an eye on the temp gauge....

[Neu]

Looks like I'm doing a new radiator. I'm having the exact same symptoms. I'm going to do the radiator, hoses, thermostat, belts, water pump all at the same time.

Thanks for the thread.

[Jarf]

Just curious what you guys are using for rads down there. Last time I went down this road I got an AM with metal tanks, lower tank interfered with the frame rail and the fan sensor would not seal so I returned it and went with factory.
Seems it is time to do it again, but the factory rad is now $500cdn (that is supposedly trade price!)

Can someone in the greater USA let me know what US dealers are really charging for it or what a quality direct fit A/M brand would be.
Funny, 5 years ago, with a 65cent dollar, the rad was $280, now with our dollar worth $1.02, our price has nearly doubled.
I understand inflation and material cost increases, but this feels like pure and simple greed.

Up here, we raised a lot of stink about the disparagement between CDA and US pricing, instead of correcting the situation, all they did was issue an edict that if US dealers sold into CDA they would be penalized, hard.
Now I find it hard to even get a price quote out of the US.

I have used ACH out of texas in the past (ind 3rd party) they charge large too (20% on top) but the last time I used them I still saved over 40% (after it was landed) compared to my CDN dealer.
I do not fault the dealer level, the price structure seems to be issued from Toy CDA.
I took in my invoice and my parts guy was not happy, he showed me his cost on the parts I had bought and my landed cost after shipping and duties was still about 20% below his cost.

[Petros]

last time I bought a new radiator, a double row A/M with plastic tanks, it cost me $140 from a local dealer here in WA. That was about 4 years ago.

The factory radiator should last a long time if you flush it every two years and do not abuse it. What failed on yours?