Questions and Answers

Toyota Van Problems Q. Hi, I'd like to ask a question about my girlfriend's Toyota Van. The problems, maybe related, maybe not:

• Gets very hot (but not the red zone on the gauge) when my girlfriend drives to work which involves driving up a steep hill at 25-40 mph for some distance.After overheating in his manner, it spits lots of coolant into the overflow reservoir as it cools, overflowing the reservoir. It spits out enough coolant so that we have to constantly add coolant if she drives the van to work. We often don't have to add coolant if I drive it around town (flat) where it doesn't overheat and it doesn't leak coolant sitting in the driveway. A mechanic did not find any coolant leaks (other than the reservoir overflowing when it overheats).
• Does not overheat on flat ground or at highway speeds.
• The radiator fan appears to run all the time. I'm not certain about this but when I've cold started it in warm (not hot) weather, the fan starts immediately (A/C is not on and not working).
• Start Time Injector Switch has infinite resistance (i.e. out of spec).

The Van:

• 1984 Toyota Van w/A/C (doesn't work).
• 200,000 miles
• New engine and rebuilt water pump were installed at 150,000 miles.
• Radiator was either replaced with a rebuilt or professionally cleaned/recored at 150,000 miles. New transmission at 165,000 miles.

My attempts to fix the problem:

• Replaced the thermostat (which was sluggish in opening).
• Drained and replaced the coolant. Could only get ~3 q. out of the van (7 quart capacity). The coolant was in ok shape (not particularly dirty without a lot of particulate matter).
• Tested the water temp sensor and found it ok.
• Tested the Start Time Injector Switch (it's in the same housing as the temp sensor) and found it to be bad (infinite resistance).

Note about these sensors and others. Because the van is ageing (despite many repairs), the wiring harnesses to these sensors are deteriorating. I haven't replaced them as it would be very expensive and time consuming (and they generally seem to work). Could this be related to the problem?

I've fixed lots of stuff on this van and it is in many ways in better shape than the age would indicate, but am a bit puzzled as to where to start.

My questions:

1. Any suggestions for the overheating problem specific to driving uphill at moderate speed?

2.What does the start injector time switch do? If we aren't having any starting problems (we live in San Jose so it is not cold out), what benefit would there be to replacing it ($150 part)?

3. How can I test the fan clutch since it seems to run all the time? Is there a sensor or something other than the clutch that could be causing the problem since I would guess that fan clutches usually break in the opposite manner (i.e. the fan no longer works)?

4. Could this minor overheating (the radiator doesn't not steam, not in the red zone etc) damage the head?

Any suggestions would be much appreciated!

Thanks!

Keith

A. Okay Keith, in order:

1. This van is giving all the signs of a restricted cooling system. The additional load on driving uphill for an extended period of time is just too much for the cooling system to handle. Under highway conditions and local driving, it can keep the engine cool. I would suspect that even though you had the radiator cleaned 50,000 miles ago, it may be at the end of it's useful life. I would let it get hot and feel the front of the radiator and see if it is equally hot over the entire area. It will be a little cooler down low, but not cold. If you feel cold spots or a large cold area, it's shot.

2. The start injector time switch (thermo time switch), cold start injector and auxiliary air valve all come into play when the coolant temperature is below 95 degrees. This is the "choke" system of a fuel injected engine. When the engine is cold, it needs a little extra shot of fuel to start and a higher idle speed. Depending on temperature, the computer will activate the from anywhere from two to six seconds. The AAV will give the initial high idle and gradually decrease it as the coolant warms up.

So you can see, "cold" is relative to an engine. If it starts up fine and is causing you no problems, then let it slide and put it on your list of things to do when time and finances permit.

3. The best way I've found to test a fan clutch is by listening to it. When you first start the engine it will make a roaring sound that will disappear in a short time. When it is making that sound, the clutch coupling is engaged and driving the fan. When the roar stops, it has disengaged and the fan is no longer being driven. As the engine runs and the coupling heats up, you will hear it roar again as it engages.

The electric cooling fan works off a temperature switch in the radiator. When the coolant temperature reaches a certain point, the switch closes and sends power to the cooling fan. When the temperature drops below the set temperature, it opens and shuts off the fan. If the fan is on constantly, chances are that switch is bad.

4. Could this damage the head? Not in a direct manner but, yes. Aluminum heads expand and contract a lot more then a cast iron head and thus are more prone to warpage. This warpage could eventually lead to head gasket failure. If this is the case then the head needs to be resurfaced to get the head gasket surface area perfectly flat again. In the short term, I don't think you have too much to worry about in this area.