engine heating with aircon on

[john_d]

I have a PZJ 70. I replaced the old leaky radiator with a new genuine Toyota radiator, when I bought this vehicle last december.

My problem is that the engine overheats( temp needle goes above the 3/4ths mark) in the afternoon(30-35c), with the aircon switched on. The engine temp starts to climb even with normal driving but especially if I'm idling in traffic. When the engine starts to overheat I switch off the aircon and the temp seems to come back down to normal after a few minutes.

The engine only overheats when the aircon is switched on and not when it is off. Also, the problem only seems to occur at slow or standstill speeds with relatively high ambient temps.

Could someone please provide me a checklist to diagnose this problem?

 

[crushers]

clutch fan working properly (do a search)?

 

[roscoFJ73]

Could someone please provide me a checklist to diagnose this problem?

Always start with a new radiator cap and make sure all the hose and clamps are tight and leak free
A good sign is when a coolant system builds pressure within 5-10mins.
x2 on the clutch fan.

 

[john_d]

The new radiator has a new cap as well. There seems to be no leakage in the cooling system. However, there has been a decline of about 2 to 3 cms of coolant fluid from the reservoir over a few months.

It does not use a clutch fan.

In addition to the above, the engine is also consuming oil at the rate of a 1ltr every 1000krms. The exhaust is smokeless, there's no oil or smoke from the dipstick sheath and the engine compression seems decent enough. I just had the diesel pump rebuilt and the vehicle has only travelled 160,000kms.

The local mechanic claims that both problems: engine overheating and engine oil consumption are related to using a different grade of engine oil from that of the previous owner. I'm extremely sceptical but I'll change the engine oil and see what happens.

There is also a thumping noise emanating from the engine which I've been unable to troubleshoot. I had the head removed and valves lapped because we suspected valve leakage. However, the thumping noise persists. I also read somewhere that the thumping noise could be because of low compression.

I'd love to replace the engine and do all sorts of things but I'm in Nepal where spare parts are hard to come by and facilities are rudimentary, to say the least.

 

[crushers]

you have a fixed fan coupler? just asking to confirm...

 

[john_d]

yes, it's a fixed fan coupler.

 

[crushers]

hummm, new rad, new cap, fixed fan, new hoses...
you also say it is eating 1L per 1000KM (not a biggie at all)
2-3cm over a few months could be evaporation so i wouldn't worry about that one.
thumping...interesting. from botom end or top? have you tried the stethascope trick to locate the exact spot?is the thumping at idle? low rpms? high rpms?

the PZ is a tough old motor but i have never had a "thumping". i have had heating problems on the old tractor but it turned out to be mud traped between the AC rad and the cooling rad. so that doesn't help.

interesting.

 

[john_d]

The thumping noise is ever present. It increases or decreases in tempo with the revolutions of the engine. It becomes very loud when the air filter canister is opened.

 

[crushers]

open the canister and video the sound and post it up... i know my PZ has a good thump when the canister is open and now with the snorkel it has a good thump 2 feet away from my ear... common with all the PZ engines... are you sure it is a problem and normal?

 

[roscoFJ73]

You will get more hits posting diesel questions on the diesel forum.

 

[john_d]

can this thread be shifted to the diesel forum?