Overheating

[Alfredo20]

I been having overheating problems with my Nissan patrol pickup 1983 td42 I fixed it a couple of times but I am back to the same place after a week until I found out this cars can’t be without a thermostat mine doesn’t have it it’s straight radiator to thermostat housing back to radiator I can post pictures if anyone can help me out. I taken it to around 6 mechanics and all have fail, it maybe because i am from Guatemala and to be honest it’s the only Nissan patrol pickup td42 I seen so far. I want to fix it one more time and hopefully the last time before I give up and sell it. Anyone can guide me step by step?

[Peter Connan]

Alfredo these engines require all elements of the cooling system to pe in very good condition as the cooling system is marginal at best.

The original thermostat is a double-valve design with a second moving disc at the bottom. There is a bypass in the thermostat housing. When the car is cold, the coolant is circulated through the head only. But the sealing surface which is part of the thermostat housing wears away.

Quite often we plug that bypass passage and replace the thermostat with a conventional one with a 76 degree temperature rating.

In addition, the radiator has to be in good condition, the viscous coupling has to work correctly (these can be re-filled with viscous oil if needed) and the water pump also needs to be in good condition.

[Alfredo20]

Alfredo these engines require all elements of the cooling system to pe in very good condition as the cooling system is marginal at best.

The original thermostat is a double-valve design with a second moving disc at the bottom. There is a bypass in the thermostat housing. When the car is cold, the coolant is circulated through the head only. But the sealing surface which is part of the thermostat housing wears away.

Quite often we plug that bypass passage and replace the thermostat with a conventional one with a 76 degree temperature rating.

In addition, the radiator has to be in good condition, the viscous coupling has to work correctly (these can be re-filled with viscous oil if needed) and the water pump also needs to be in good condition.

Is there anyway you can help me out step by step the radiator is brand new the water pump I’m not sure which one it has is there a better upgrade if need it? Is there a way to check the water pump before I even try to replace it and it doesn’t have a thermostat I am not sure if the thermostat housing is still good if you have experience on them I can send pictures also since I am in Guatemala I am not sure there’s any replacement for them here so I have to order them from the USA or somewhere if you can guide me I will gladly appreciate you.

[mvcoller]

Alfredo,

Funnily enough I just sent this link to Peter Connan last night about the subject.

Watch the video, you will pick up some very good tips there re the water pump (how to measure it), fan and you will also see the double seat thermostat. Seems the genuine water pump is desirable.

[Alfredo20]

Alfredo,

Funnily enough I just sent this link to Peter Connan last night about the subject.

Watch the video, you will pick up some very good tips there re the water pump (how to measure it), fan and you will also see the double seat thermostat. Seems the genuine water pump is desirable.

Hmm I seen that video but I not my radiator to his is way different I will seen pictures and I will try to send pictures later on on the thermostat housing and how it’s completely open doesn’t have a thermostat, Peter said I should buy a 79degree thermostat I’m just trying to find a pal to guide me step by step I have only had Tacomas never this Motor they said it’s one of the bests but I can’t get it out of the overheating I have never had an issue with the other cars and since it’s a rare car here in Guatemala even worse there isn’t many with experience

[mvcoller]

Peter said: "Quite often we plug that bypass passage and replace the thermostat with a conventional one with a 76 degree temperature rating."

Not 79 as you said.....

- Is your water pump OK, did you measure it as they did? Measure how close the impellor is running from the block? I think the first water pump they measured was 2.5 mm away, the new one was just under one mm. They chucked the first one away, even though they said it looked as if it was fairly new and recently charged.

- Did you check if your aircon condenser is not blocked or partially blocked, preventing air from cooling the radiator down sufficiently.

- Do you still have the bottom part of your radiator cowling fitted. That is UBER important for the fan to be able to extract the hot air away from the radiator, and push it into the engine bay to enable it to escape underneath the vehicle.

- Does your viscous coupling fan still work effectively? If you turn the fan by hand, does it offer some resistance? If not, it needs to be replaced or you need to fill it with the correct fluid. Ask radiator specialists how to do this.

- Get a 1.1 bar or even a 1.3 bar radiator cap. The extra pressure helps - You may wonder about this.

The main reason for a pressurised water cooling system is for the water to be "pressed" hard against the metal on the inside of the head, the metal parts inside the block and the outside of the sleeves. If it is not hard against it, the water at the contact point will boil and no longer be in contact with the surface. (look inside a kettle when it boils..... the water makes an air bubble against the metal, keeping the water away from the kettle surface, creates steam and warms the water up more and faster). When that happens, the water cannot extract heat from the metal of the engine, which means no cooling takes place and the engine will overheat and boil.

One other thing we did when I raced cars on the track, I fitted a 67 degree thermostat, so that it opened 9 degrees earlier, thus starting to circulate water sooner keeping the engine cooler and keeping it cooler. With you not running a thermostat, that will not apply to your situation.

Another reason for petrol engines running too hot is when the air fuel mixture is too lean. In diesel engines, I think it is the opposite. More air and less diesel cools down the combustion process. Maybe someone here can confirm this

Good luck...

[Peter Connan]

Here is the thermostat housing:

The surface at the tip of the punch in above photo needs to be a flat, machined surface. It's a bit difficult to see, but on this one the surface is pitted and damaged. When this happens, water by-passes the radiator and cooling is compromised.

In this photo, the punch is pointing to the welsh plug which is fitted to prevent water by-passing the radiator. However, as mentioned, when this is done a different type of thermostat must be fitted.

Unfortunately I do not have photos of the thermostats, nor spare ones lying around.

[Alfredo20]

Here is the thermostat housing:
20230220_155456.jpg

20230220_155512.jpg

The surface at the tip of the punch in above photo needs to be a flat, machined surface. It's a bit difficult to see, but on this one the surface is pitted and damaged. When this happens, water by-passes the radiator and cooling is compromised.

20230220_155519.jpg
In this photo, the punch is pointing to the welsh plug which is fitted to prevent water by-passing the radiator. However, as mentioned, when this is done a different type of thermostat must be fitted.

Unfortunately I do not have photos of the thermostats, nor spare ones lying around.

Wow this is what I am talking about this is great help I will be working on the car probably on Wednesday first will be the thermostat housing I will be sending you pictures if you don’t mind??

[Peter Connan]

I don't mind but please note I am not on the forum all day.

If you need a rapid response, email me. I will PM you my mail address.