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Foster

Geo Tracker Lost Heater Function

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I have  92 Geo Tracker, 1.6 Lt. 5 speed. Last fall I replaced the head since then the vehicle won't warm in the winter (even with cardboard covering the radiator, the needle never goes past 1/4) and runs too hot in the summer, I have to keep the heater on.

I've replaced the thermostat twice and just replaced the water pump, no change. (the old water pump looked just fine.

I checked the temperature at the thermostat (with infrared thermometer) when it is running hot, on top of the dome it reads 194 and at the bottom of the thermostat 234. The lower rad hose is considerably cooler 164, the radiator cap reads 145.. 

I've checked all the lines that carry coolant and they seem to be connected properly. I've also check the thermostat in a pot of boiling water and a candy thermometer and it opens at around 180.

I am completely baffled, if anyone out there has any ideas please post them.

Thanks in advance

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Foster...Sounds like a clogged heater core if the vents, traps and blower are working properly.  You've done all the right things with troubleshooting and addressing trouble points. 

 

If you have a pair of heater hoses with fittings at the firewall, use your infrared thermometer to check temp of the two hoses away from engine heat.  There should be a slight temp drop on the return hose.  It's tricky to read hose temp due to insulation factor, but try here.   

 

I had an issue with our XJ Cherokee 4.0L that's worth sharing.  The heater was simply blowing cold air.  I ran similar tests to yours and went a bit further.  The radiator had been leaking and a "non-clogging" stop leak had been an emergency fix.  I narrowed the issue to a clogged heater core.  Bought a reverse flushing device and supplemented it with compressed air.  Here's the procedure I took to avoid damaging the radiator core:

 

1)  Disconnected both heater hoses (pressure and return hoses) at the engine end.

 

2) The flushing tool hooked to a household garden hose, and I charged the open system from the return side hose to provide a "reverse flush" effect.

 

3) I carefully supplemented each charge of water with a charge of compressed air, just a short burst and light on the nozzle!

 

The water first came out sluggishly, in bursts.  I kept going, always being careful not to apply ultra high water or compressed air pressure.  Keep in mind that the core only has to hold 20 PSI or so normally.  Household water PSI can range from 40-65 PSI, typically.  Compressed air can be much higher if not regulated.

 

Eventually, the water flowed through the hoses freely after the clogging gunk had ejected.  Once coolant flowed freely after reverse flushing, the heater has never worked better!

 

As for the connection between the head replacement and lack of heater function, a strong possibility is that RTV sealant and gasket sealant from the head work circulated through the engine's cooling system and heater hoses.  The heater core got clogged...This will come loose if you reverse flush.

 

Moses  

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Hi Moses:

Thank you for your interest, I think you may have misunderstood my problem, my heater works fine. it is the engine that either runs cold in the winter, or too hot in the summer, (see my original post). Unless I am mistaken, I don't see how a faulty heater would affect the engine. Quite frankly it is like the coolant is not circulating through the engine even though the water pump is working fine. I guess my next move will be a flush on the radiator and engine.

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I did miss the point...This is interesting...If the engine ran hot all the time, it might be easier to diagnose.  The running too cold in the winter is strange, especially considering the number of remedies you've tried.

 

From your temp readings, it sounds like the radiator is cooling the liquid effectively, top to bottom.  It seems like your coolant flow into the radiator is restricted, though.  234 at the base of the thermostat is a bit high.  194 at the top would be normal for a 180 degree thermostat...What is the temp along the upper radiator hose and near the radiator inlet neck when the engine is running "hot"?  Is the thermostat facing the correct direction?  Sounds elementary, but this can often be an issue after service work.  A clogged radiator usually causes overheat in hot weather but will not cause the engine to run cold in the winter...

 

Where is the temp sender located?  Take some surface temp readings along the engine block (away from the exhaust) and along the cylinder head.  See if there are any exceptionally hot or cool areas.  One thing that can cause irregular flow is a head gasket either installed wrong (backwards or upside down) or a gasket that is incorrect for the application.  If the circulation ports between the block and head do not match, circulation with be abnormal.  Was this an "exchange" head or the rebuild of your original cylinder head?  Are you confident this is the correct head for the block?  Check the casting number and compare.

 

If you're relying on the temp gauge to determine the engine temperature, take temp readings near the temp sender and compare the reading with the dash gauge reading.  There could be locally poor circulation at the engine that makes for an inaccurate gauge reading. 

 

Let's keep this conversation going until you resolve the problem, Foster.

 

Moses 

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I am in the middle of doing a 3 day flush of the rad and engine, using Prestone, Flush + Cleaner.

I can tell you it is the original head, and no the head gasket is not in upside down or backwards, I made that mistake years ago, never again. The thermostat is in the correct orientation.

It was brought up to me that I may have fixed the first problem, running cold in the winter, which led to the second problem, overheating in the summer. I mentioned that I changed the thermostat twice, well I kept the original thermostat because it looked fine. When I did the boiling water test, I tested both the new and "old" one. They both opened at 180 but the old one seemed slower to close, so I tossed it.  This may have fixed the cold running problem, but left me with a blockage in the radiator or engine, so I'm doing the flush. I did the thermostat swap in late spring early summer, and did the pump swap about 2 weeks ago. The tracker is not my regular vehicle so I tend to put of repairs. I'll let you know how the flush goes. 

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Genuinely interested...Keep us posted on the flush results...Thanks for clarifying the head and gasket, that's off the list now...

 

Moses

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Finished the flush, lot of crap came out when I drained the system. unfortunately the Tracker still runs hot.

I did find something interesting, I discovered the Flex fan is still loose (free wheeling) even with the engine hot.

This is my last hope, I'm going to our local Pull and save wrecking yard and hoping to find a fan clutch that works, the yard has 5 Tracker/sidekicks, maybe I'll get lucky. If not Ebay has one for $45.00 with free shipping.

Not sure where to go after this if a new fan clutch doesn't solve the problem.

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Very important discovery, Foster!  This could account for the overheat/running hot in the summer, for sure.  If the fan clutch drags in the winter and keeps the fan on too much, that could also be the reason for running too cool.  I think you may be onto something...Good sleuthing and troubleshooting!

 

Let us know how the new or used fan clutch assembly works...

 

Moses

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OK, I got 2 fan clutches from the salvage yard, both seem to be in good shape. I have tested both of them with the same results. The tracker runs at the normal temperature (the needle about 3/4 to the mid point) for 10 to 15 miles, then slowly creeps to the mid point and a little beyond. This is not the normal way the tracker ran in the past. Also if I put it under load, going uphill, it goes even higher.

I took temperature readings after my last run, parking the Tracker and letting it idle. Here are the results. Top of thermostat housing, 200F, bottom hose, 195F, top of radiator, 187F, radiator cap, 160F, water pump, 197F. I have no real idea what these numbers mean. I know the thermostat is supposed open @ 180F, so I'm guessing the coolant shouldn't get much hotter.

Some interesting things I noticed, when I slowed down to make a sharp turn then sped up, the temp gauge fell way back (almost to the 1/4 mark) every time I pushed in the clutch and up shifted. When I reached 5th gear, the needle was back at just past the midpoint. This didn't happen if I just pushed in the clutch while driving or when I down shifted. I took a stick  and slowly pushed it into the fan, I was able to stop the fan with very little resistance, in fact I think I could have done it with my hand and it probably wouldn't have hurt me.

The overflow tank was filled to about 1/2 inch below the full line when the engine was cold, and about 1/2 inch above the full line when I parked and took the temp readings.

Cruising the internet, I've learned more then I've ever wanted to know about thermally activated fan clutches, they are often under filled, from the factory with the silicone oil that makes them work. You can put more oil in the clutch, but the pictures didn't match mine so I'm not game to try that. You can't bench test them without some sophisticated equipment (the clutches work on both centrifugal force and temperature.

I am hesitant to purchase a new clutch, unless I am absolutely sure the ones I have are bad. I'm wondering if I should replace the temp gauge or sensor, after the strange needle jumping as I up shifted.

I open to any and all suggestions.

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Foster...The strange reading at the gauge could be a defective sender.  Before replacing the sender or testing the gauge wiring, have you had the radiator professionally rodded/cleaned?  Did you flush the cooling system thoroughly?

 

Are you running the A/C when this weird temperature change takes place?  This could be a charge of cooler air through the condenser and radiator core when engine speed changes.  That hints of radiator hot spots.  Take your infrared tester and aim it at the rows of tubes in the radiator core.  See if there are dead areas of either hot or cooler flow.  That would indicate clogged tubes. 

 

The temp sensor can be tested with a simple ohms resistance check.  The values should be in a factory shop manual or maybe shared online.

 

Thanks for the update...

 

Moses

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