3,9 V8 overheats when idling

[stobbie]

We have a Defender here that we have converted to 3,9 V9 automatic from a discovery.

It runs great but heats up very quickly. When we leave it idling without driving it, temp goes up to the last white line on the dial, so that's OK.

When we drive it it's around that line as well. But if we have driven it and let it idle after that it start going up and goes just over the red mark.

The engine has been reconditioned with all new bearings, piston rings, seals, waterpump, camshaft etc. It has a new 19J TD radiator, but we have now discovered that the radiator has a little bend on the underside, could that cause troubles with the water flow?

I've now taken the visco fan off and replaced that with two 150 watt electric fans, that helps a few degrees I think, but not enough.

I've just done a test for combustion gasses in the coolant and luckily there are not.

I've taken the heart out of the thermostat to see if that makes a difference, it doesn't.

We have a puma bulkhead in this car, with puma heater and aircon. The routing of the hoses was a little difficult and I was affraid there may be some air left in the system but the heater heats up within a minute of starting the cold engine, even without the thermostat. That seems strange to me as well..

Anyone ideas?

[finnarne]

Are you using the temp sensor from the original engine, or are you using the one that came with the new engine. And the same with the gauge ?

I 've changed from 200tdi to 300tdi in my car, and the gauge was way off. Bought a set of 3rd part gauge/sensor, end now the gauge stays at ~80°C when idling after the engine has heated up. When it get warm its goes up to close to 100°C.

With the sensor that came with the 300tdi, and the gauge that is from the 200tdi, the gauge read "very hot" when the gauge now says 80°C. End whenever I played in sand or went up a hill, the red warning light started to flicker.

[Snagger]

Yep, my money is on the sender being incompatible with the gauge. You need the vehicle's original sender in the engine, and expect it to show slightly warmer than middle if you have converted from a diesel and petrols run a bit warmer.

The engine's original fan will do a much better job of cooling the rad and engine than electric fans, as long as the viscous coupling hasn't failed "open", so I'd refit it as long as it is safely clear of the chassis and rad, and the rad cowl fits the V8 fan position. The only advantage with electric fans where an engine driven fan fits correctly is being able to switch them off for wading.

[stobbie]

I have used a 300tdi Defender sender with a 300tdi gauge, so that should be OK..

[Snagger]

In that case, I'd look into the normal running temperature of a Tdi, which I think is around 90oC (88o thermostat) and a V8, which will be warmer. If it's too close to justify the gauge readings, I'd take a close look at the water pump and get the coolant checked chemically for exhaust gas contamination - it'll show whether there is and exhaust gas getting in through a crack or bad gasket.

Can you post up a photo of the rad damage? Your description makes it sound insignificant, but V8 rads are bigger than 19J and opinions and descriptions of damage are highly subjective.

[Bowie69]

V8 is around 90C as well, so I'd be looking elsewhere.

If at all unsure of the actual running temperature, buy a matched pair of sender/gauge, the that way you can be sure.

[stobbie]

I'm now going to try with another new sender and old gauge..

Here is the engine bay and the damaged rad:

[Bowie69]

Rad damage is inconsequential.

[dave88sw]

My dad has a 2.5td rad and a brand new V8 defender rad in the garage, the v8 rad is almost twice as thick. Before you do anything though, if you have access to a lazer thermometer, check to see what the actual temperature is in the top hose.

[stobbie]

I've left my thermometer at home at the moment :-( . But it is hot. The fan switch switches on at 90 degrees and switches off at 80 degrees again. When I leave it idling the fan comes on and never shuts off again, temp barely goes down. Heater on max and aircon fan on does barely help.

I know the discovery has a much bigger rad. but we have used 19J radiators on most conversions and have never had a problem before.

Is there another rad with oil cooler that is a better fit?

[Disco-Ron]

With that fan switch the fan will never go off...... you need a switch that goes off at regular running temp..... 80 is far too low...

[disco2hse]

The engine has been reconditioned with all new bearings, piston rings, seals, waterpump, camshaft etc. It has a new 19J TD radiator, but we have now discovered that the radiator has a little bend on the underside, could that cause troubles with the water flow?

Was the radiator rodded before the rebuild?

I've now taken the visco fan off and replaced that with two 150 watt electric fans, that helps a few degrees I think, but not enough.

The viscous fan usually does a better job of cooling, especially when it is properly cowled. Can't see from your photos if the cowl is set correctly.

I've taken the heart out of the thermostat to see if that makes a difference, it doesn't.

The thermostat remains closed until the coolant reaches the correct temp, then opens to let the coolant flow out of the top of the engine. In other words, it helps to heat the engine quickly from when it is cold, not to cool it down (but it does that too of course).

We have a puma bulkhead in this car, with puma heater and aircon. The routing of the hoses was a little difficult and I was affraid there may be some air left in the system but the heater heats up within a minute of starting the cold engine, even without the thermostat. That seems strange to me as well..

If an air lock exists, It may be possible that the coolant is not circulating correctly. An air lock would inhibit the flow of coolant. I would bleed the plumbing from the highest point.

Other suggestions around senders notwithstanding.

[Mo Murphy]

If 90° is the normal running temperature, then surely that should be your fan cut off temperature rather than switch on.

I'll put in another vote for a properly cowled viscous fan.

Mo

[stobbie]

I cannot find a cowling that fits properly.

The fan switch is not ideal, but at this moment it is only good if it keeps running, so it has a little extra cooling. When the overheating problem has been solved I can start looking for a better switch range.

Without the heart of the thermostat there is a slightly bigger opening than with the thermostat fully open, so it might help cooling a bit. But therefore it is strange that the heater is warm within a minute, it should take ages without a thermostat.

I've filled the cooling system through the heating hoses, that is the highest point in the system. I don't think there is an airlock now..

I've just fitted another new sender, and another gauge with a few wires underneath the hood, to eliminate wiring and it has the same temp as the other one..

[Disco-Ron]

I might be barking up the wrong tree but....

Could the fact that the puma heater seems to have a valve that closes the water flow have an effect? .. the earlier ones have a flap that blocks airflow. .. therefore the bypass element til the engine warms up is blocked.... Could that explain it heating up so quick?...

Just a random thought

[stobbie]

Maybe, but doesn't affect the engine temp I think..

I might try another new waterpump, don't know if it is an original one or a pattern one

[Snagger]

The cab heater system is irrelevant - an air lock in there would make the heater useless, but won't affect the engine.

I'm not sure that rad is up to much. It's not just the bottom edge that is buckled but the bottom several tubes. While their edges look fine, they may have crushed in the centre and restricted the water flow. But I'm more curious about its construction - it looks like two different cores stuck together - the lateral pipes don't match up either side of the vertical joint, and that may be causing a big restriction.

Tdi rads are about the same size as SIII rads, and SIII conversions using the original rad often struggle with heat. I think that rad is your problem, in all honesty. I'd recommend using the V8 rad.

As you can't get the cowl to fit the viscous fan, stick with the electric fans. But do make sure their thermostatic switch is in the bottom hose, not the top hose - they'll run continuously if it's in the top hose, but only when the rad isn't getting enough free flow air if you put it in the bottom hose.

[stobbie]

Thanks Snagger, especially for the thermostatic switch tip!

I may order a V8 rad, but with built in oil cooler it is expensive and this is a warranty case for us. So looking to have it sorted with the least costs. We have done lots of 3,9 conversions with a 19J rad without any problems.

I do have a new 19J rad siting here, I may try that one to see if it makes a difference.

I could try a standard V8 rad with a separate oil cooler..

[stobbie]

I have now found out that we have used a pattern stc4378 water pump. Could that have less flow than a genuine one?

[Snagger]

Possible, but it's also possible that the impeller is not secure on the drive shaft and is not spinning at full rpm. Given the cost of them versus the cost of a cooked engine, I'd suggest trying an OEM or genuine water pump if the other rad doesn't fix it.

[muddy]

Where abouts are you located? What brand is your pattern waterpump?

[stobbie]

We are in the netherlands: www.facebook.com/onetenlandrovers

I don't know the make of the pump, it is a cheap one from Paddocks, I think I will try an airtex one, at least that's cheaper to try than a new rad.

The engine is in this car:

[robertspark]

With a fuel injected engine it is not good practice to remove the thermostat (or its heart), as the engine will run in enrichment mode for longer than necessary as it won't be up to temperature as far as the engine ecu sees it.

Depending upon which engine it is, the thermostat can open at 94 deg C.... you can fit a lower opening thermostat and this is recommended, but you need to consider your ecu as it will still be looking for a higher temp before reducing the enrichment mode (over fuelling.. as it thinks the engine is cold). Is the engine block coolant sensor wired up to the ecu?

(Which ecu are you using?)

Because thermostat is supposed to open at 94 deg C, the system must run pressurised to keep it below boiling point (check it steam tables if in doubt)... hence you can have a leaking cap which is not holding pressure....

Is the serpentine belt routed correctly under the water pump pulley?

Air lock in the top rad hose?

Cannot remember if the rover v8 has any knock sensors... (will be ecu dependant) can someone remind me please (amazing what I remember and forget), if they are fitted, ignition may be trying to retard, whilst engine over fuelling, which may lead to overheating. Some waffle here, and I'm sure somewhere else http://search.lv2014.integr8cms.net/index.php/56-disc-brakes/section-9/gasofs/3115-knock-sensor

Rob

[Ex Member]

I've taken the heart out of the thermostat to see if that makes a difference, it doesn't.

The thermostat has two valves in it. One opens flow to the radiator and the other closes off the bypass flow. If you remove the thermostat, then the bypass flow does not get shut off and the flow will not be forced through the radiator.

[robertspark]

Thanks red, didn't know that with the later rover's,

Rob