Citroen ZX 1.9 Turbo D low power and slight overheating

[jvinsnes]

My 1997 Citroen ZX 1.9D Turbo 90hp runs at 80-85c coolant temp when cruising and runs perfectly fine, enough power even when towing a camper. When driving up long hills however, the temperature slowly creeps up past 90c, although never past 100c, but it gradually loses power. I suddenly realize I am foot to the floor barely maintaining 70kmh. Downshifting doesn't help. Cruising and letting the temperature drop down and the power is back again.

I've flushed the cooling system and replaced the thermostat. It seemed to make no difference. What could be causing this? I know the XUD9 is known to run hot, but why is it losing so much power just at 95c? and 80-85c seems a bit low for normal driving conditions...

[CitroJim]

The temperature rise is a characteristic of the 1.9TD when working very hard and entirely normal although, given the criticality of the cooling system toward a long-lived and happy engine it's always worthwhile to keep it in tip-top condition - regular changes of coolant of the right type and strength, flushing if need be and replacing the radiator at the first sign of deterioration. The radiator fins can also become choked with all manner of road debris... I once found a dead bird spattered against the rad! That didn't help cooling at all... If it was a goose it would have been cooked...

And most importantly of all: make sure your cooling fans work properly at both speeds.

The lack of power when hot and bothered is also a potential normal as the top-mounted intercooler is a daemon for getting heat-soaked and then it ceases to do its job and power falls of markedly. Queue in traffic on a hot day and when the road becomes clear it feels like half he engine has gone AWOL until some cool air starts moving across it again.

I would suggest you check the air ducting to/from the intercooler for kinks, blockages and correct routing. Also give the intercooler fins a good clean-out - an airline is good for this.

Hope that helps to get a resolution.

[jvinsnes]

Radiator fins are all clean and fairly straight. Same for the intercooler. Did a pressure wash of both anyways. The hood liner also seemed fine. No sagging or anything else that would restrict it. Although now that you mention it, I can't remember to have ever heard my fans running... That'll be the next on the list. I also have a bigger FMIC laying around that I wanted to fit one day, maybe now is the time. Wonder if there is enough space in front of the radioator? Looks like there is enough behind it, but that's probably not doing it any favors. Can you get much more power out of it with just an intercooler upgrade and pump/turbo adjustment? Mine has a cat and the Lucas pump if it makes much of a difference. 90HP aint to bad from what I am used to, but a little bit of an extra kick would be welcome when towing a camping trailer.

[CitroJim]

Yes, do check the fans as if they are not working then intercooler heat-soak could be made worse...

An FMIC may help but yes, depends upon room for it and the ability to neatly plumb it in. The standard FMIC fitted to say, the Xantia, is a lot larger than the top-mounted one and may give a small but useful gain. Remember, they too are compromised by being behind the coolant rad.

[jvinsnes]

I did quite a bit of testing and found that the fans don't turn on when they are supposed to. One test involved foot to the floor up a hill until the power dropped so much I had to stay in 4th gear 2500RPM just to keep my speed. As I stopped, the coolant temp had reached 100c and I could not hear any radioator fans. Opened the hood to double check and comfirmed the fans were indeed not spinning. Until yesterday. Just a quick trip to the store and the temp had not even reached 90c when I shut the engine off. Lo and behold, I could hear the fans running loudly and they ran for 5-10 seconds before slowly ramping down. I swear this is the first time I have ever heard the fans running. It is hard to miss. I am thinking there could be a faulty temperature sensor somewhere. Any ideas on where to start? I am also looking at the possibilty of adding a hood scoop to the TMIC and cutting some plastic to direct all the air from the grille to the radiator. It looks very restrictive. I can't image how the older models were dealing with the heat seeing that the grille is almost completely closed on the early style hood.

[CitroJim]

Does your car have aircon?

If not, it's likely the fans are under the control of a three terminal temperature sensor screwed into the radiator... These are a common failure point. At least you know the fans themselves do work.

They should be two speed - slow when the temperature raises a bit and then fast when things get really sweaty... The temperature sensor slow bit is the first half to fail.

If you have aircon, it's a totally different ball-game. The fans should run all the time the aircon is on and are under the control of the aircon ECU.. Fans can be tested by disconnecting the brown temperature sensor with the engine running. If all good the fans will run at top-speed. Aircon cars have three temperature sensors - a blue one for the gauge/overheating (engine cooked) warning light, a green one for the engine ECU and the aforementioned brown one for the aircon ECU.

[Dommo]

Lack of rad fans is certainly not ideal, but here's another thought... I note on your photos you have large spot lights mounted up front, as standard the top mount intercooler doesn't have a huge amount of ducting to allow air to cool it. So could the spot lights be partially blocking the airflow to the intercooler ducting? It certainly won't be helping your aerodynamics either so it could be that the engine is fighting a losing battle there, the ZX has a fairly aerodynamic front end as standard.

[jvinsnes]

I eventually removed the lights and have not experienced this problem since. Fans still don’t work, although it keeps a steady 85c even uphill and no low power issues now. Just stashed the car away as a new car took it’s spot in the garage. On another note, I aquired a Bosch injector pump from an 80s Toyota corolla. Wonder how much work it would be to replace the Lucas? It doesn’t have the proper bracket and injector lines as it would if it came off of an XUD…