Engine "underheating"-Toyota

[disco stu]

So I know its a Toyota, but I figure you guys could still help, plus the design between the 2 engines is so similar it makes me think they are designed by the same team.

So this is a 1998 camry with 1mz 3L engine. I did have overheating issues in the past which turned out to be radiator. Before that it was alright, but with new radiator it now doesn't get up to temp in winter. It will rise up going up the hill on the way to work, but on flat roads it is hanging just above the coldest on the temp gauge. In summer it is basically mid way point on temp gauge all the time.

I pulled out the thermostat last night to check it, and it just started to bump open at about 75deg, rated at 82deg. Still, going by the heater temp its not getting up to 75deg (brrr in winter, unless driving up a hill). Heater core is likely a bit clogged, but it blows warm air when the temp guage shows its up to temp.

The fact this changed when I changed the radiator means this was what started it, but its not like I installed a king kong radiator (it was a cheapie). Also, by my understanding, the only way the water can get through to the radiator to cool it down is through the thermostat, so regardless of the outside temp the engine should still warm to the same point, and thermostat only open when it gets up to that point. But going by that the temp should be up at around 75deg plus.

It runs on LPG. Not sure this would make that much difference.

Any ideas whats going on with this, or ways to get around it? Tempted to block radiator hose, not sure what else to do

Thanks in advance

Stuart

[Kingbrown]

Something that comes to mind is the balance of hot coolant that is shared between the radiator and the heater core.

If your new radiator's water circuit offers less resistance than the original then your heater core might be starved of hot coolant.

Doesn't matter how hot the coolant gets, If there isn't enough flow to the heater then your heater won't be able to deliver heat to the cabin.

Experienced something similar when trying to balance oil feed to several plain bearings on a very large fan/motor.
When oil was cold you would flood particular bearings and when hot the flow/lubrication became marginal. A tricky balancing act with a raft of adverse consequences if you got it wrong.

[nj swb]

I pulled out the thermostat last night to check it, and it just started to bump open at about 75deg, rated at 82deg. Still, going by the heater temp its not getting up to 75deg (brrr in winter, unless driving up a hill). Heater core is likely a bit clogged, but it blows warm air when the temp guage shows its up to temp.

It runs on LPG. Not sure this would make that much difference.

Any ideas whats going on with this, or ways to get around it? Tempted to block radiator hose, not sure what else to do

To me, things point to the thermostat not regulating temperature like it should. Under low load, it's flowing enough for the radiator to "over cool", but as load increases the system starts to regulate properly.

Does the thermostat have one of those little "air bleed" jiggle things?

Next suspect is the LPG converter. I believe these are typically heated by the engine, to avoid freezing under low load by evaporation of the gas. Is this system flowing coolant independent of the thermostat? I'm not sure why it wasn't a problem with the old radiator, but I guess stranger things have happened.

[Dicko1]

Get a thermostat that opens in the 60,s degrees area. They are cheap and will confirm if the thermos working as it should.

[benckj]

In the old days we use to put a piece of cardboard in front of radiator during winter to increase the temp of engine and heater core. Might be worth a try to see how your system reacts.

[erad]

The heaters on cars these days do not have a valve controlling the water flow through the heater core. Instead, a flap diverts incoming air past the heater core, or through the core, depending on what you have selected inside the cabin. The flap may be disconnected, or not closing enough to force air through the heater core. Also, your heater core may be choked up with crud, thereby blocking airflow through the core.

[geopaj]

The heaters on cars these days do not have a valve controlling the water flow through the heater core. Instead, a flap diverts incoming air past the heater core, or through the core, depending on what you have selected inside the cabin.

Its not just "cars these days" with that style of heater. My 1973 HQ Holden's heater is the same - coolant constantly flows through the heater core and there is a flap that diverts air either through or around the heater core.

[stumagoo]

I would be looking at the thermostat and that you dont have an air bubble in the coolant.

[Pajshomoneroguntero]

I'd say the issue is not with the heater circuit as you've mentioned that the water temp isn't coming up. If the water isn't warm then the heater circuit won't be able to transfer heat into the cabin.

[nj swb]

In the old days we use to put a piece of cardboard in front of radiator during winter to increase the temp of engine and heater core. Might be worth a try to see how your system reacts.

If too much heat is being lost through the radiator, perhaps he needs a radiator insulator?

http://kalecoauto.com/index.php?main_page=product_info&cPath=11&products_id=43&zenid=arDjE5nnbR2-lDgtgEJXv3

[erad]

As the vehicle runs on LPG, the gas converter draws coolant from the system as well, so that tends to cool things down even more than on petrol. This is minor though. As above, it seems as if your thermostat is not hot enough. Not sure about Toyota, but Mitsubishi petrol engines thermostats start to open at 76.5 Deg C and are fully open at 90 Deg C. The GDI petrol engines are even higher - 82 - 95 Deg C.

[disco stu]

Thanks for the replies all. I'm currently away, but will reply better when I get home and have computer to read through and type properly

[dhula]

Put a new thermostat in
Put a new rad cap on
Make sure coolant is full, bled properly and at the right concentration


If still have problem after doing all that report back and we can go further

[disco stu]

Sorry for slow response everyone. Been flat out.


I swapped thermostat when I originally had it out-very slight improvement but problem not fixed. I haven't changed cap but in all honesty I can only see radiator cap causing overheating rather than underheating. Cooling system all bled, but once again I've only ever had overheating issues in the past from these issues-they have never caused my cooling system to work better than intended.



I thought the radiator cover to keep the heat in was weird, as they advertised it to keep the energy in the engine-there is a reason we need the radiator and that is to cool things down. But, I thought the logic was very strong for my issue considering that mine all started with new radiator (still can't understand why thermostat isn't fixing the issue-might be because thermostat is on the engine outlet to the radiator rather than on the inlet. Tempted to put second thermostat in the top).



The solution was actually very simple-unbolt radiator and tilt it back, cut up an old sheet to cover 1/3 of the radiator, put that over the little knobs that that the hold down bracket sits over, bolt radiator back up and the rag is now held in place covering 1/3 from the top of the radiator.


Driving along it now sits at where it should-gauge at about halfway except for the coldest mornings on faster runs going slight downhill so the engine isn't working, it sits not far below where it should in those circumstances, not right down at cold like it was before. Got warm air coming out of the heater, so I'm a lot happier on those cold mornings too.


One interesting thing-this is the first full tank of LPG since making the change. After new multivalve put in I was getting about 310km/tank LPG (not happy, need to fix the pick up, but different story). I'm now at around 380km on this tank of fuel and still going, but I'll need to fill up tonight regardless (60km drive each way for work). That says I'm getting at least 20% better economy-I'm assuming its just richening it up due to being so cold

[erad]

Try a new thermostat - one which opens at the specified temperature. They START to open at 82 Deg C, and may then be FULLY OPEN at XX Deg C. My guess is that your thermostat is opening too soon, probably because it is rated too cold, or not closing properly.

For example, my Max Elery W/S manual states for the MPI (GCC engine whatever that is), the thermostat starts to open at 76.5 Deg C +/- 2 Deg C, and is fully open at 90 Deg C. The other MPI engines open at 82 Deg C and are fully open at 95 Deg C. The diesel engines start at 76.5 Deg C and are fully open at 90 Deg C.

Also, be aware that the temperature gauge is not linear ie the mid point of the scale is about 90 Deg C, but the red line is probably at 115 Deg C, so half of the scale is only 25 Deg C.