HOT 2.5 N/A Diesel

[tony]

Can anyone tell me why my 2.5n/a diesel is getting so hot ? I've changed the thermostat but no joy , after running it on the highway it reaches 100 degrees celsius and tries to empty the cooling system I loose about 1.5-2 liters of water . Only thing I can think of is an air lock and if that's it how do you get rid of it ? I have driven up on a 4' lump of dirt in order to "burp" the engine with no effect . Could the timing be out even though it runs great ? I did change out the fuel distributor pump for a rebuilt one .

[DaveB]

What is the pressure of the rad cap? Have you pressure tested the system?

Since 100° C is boiling point with no pressure, if the system isn't holding adequate pressure it will definitely boil out. For each pound of pressure your rad is holding, the boiling point is increased by 3° F or about 1.8° C. So if you have a 15 pound cap, that will increase the boiling point of plain water from 100° C to 125° C, which give you a margin for better cooling.

85 - 100 ° C would be in the order of safe operating range, but if its running much higher than that I'd be looking at other potential problems.

A mix of 50/50 water and antifreeze moves the boiling point up to around 120° C (depending on the brand, check the jug) which means that when it gets under 15 pounds of pressure it will boil at about 150° C (302 ° F -- pretty darn hot), which gives you an even higher margin of safety -- again providing all other parts of the system are in good shape.

Forgive my alternating between metric and standard units. I learned celsius in school for weather and room temperatures, but when I went to mechanics school all the engine measurements were in standard (still are in many cases -- ever try to buy a 1 bar rad cap?), so I still end up converting back and forth.

cheers, Dave

[tony]

Hi Dave , I did buy a new rad cap which is a 7 lb one , the Haynes manual calls for a 6 lb one , haven't tried it yet as I've just done a coolant flush with some sort of acid . I will let you know how it goes . So if it still heats up could it be the timing ? thing is it runs great .

[red90]

Is the radiator getting hot?

Check the viscous unit on the fan.

Are you using coolant? At 100 C nothing should happen unless you are running straight water. Straight water is not a good thing to use as a coolant.

It should be nearly impossible to overheat these engines on the highway in my experience.

[Glenn D.]

Don't mean to be an alarmist, but how is the head gasket Tony?

[tony]

So it turns out that you need to oil the head bolts before torquing them down with a torque wrench to get the proper foot pounds , still I figured 90 foot pounds is too little so I bumped it up to 110 foot pounds and that cleared it up . Thanks to headdamage (Andrew) for that bit of info . The compression was getting past the head gasket , pressurizing the coolant thus over pressuring the rad cap pushing the coolant out . But none of the coolant was getting into the cylinders because the head was on tight enough to keep the coolant out . Who'd a figured . Life was so much simpler without a torque wrench . Additionally never buy a cheap Allmakes head gasket get the Rover one or an German made Elring , what a difference , no more blue on start up .

[Glenn D.]

I agree the Elring head gasket is the way to go, We used an original LAND ROVER one on My 200 tdi and it weeped oil, the elring one is much better!!!!
Glad it was an easy fix tony!

[tony]

Now I have an old mystery to figure out , why is the vacuum pump getting hot enough to melt plastic ? obviously friction but why ?

[HeadDamage]

I've got a few used vacuum pumps kicking around here if you want to try another one.

[tony]

Hi Andrew , sorry I've gotten so used to dealing with Dixon I hadn't thought of asking you for parts yet , if he doesn't come through I will be calling you . Any thoughts as to whats wrong with that pump ?

[HeadDamage]

No idea other than maybe you have a leak and it is moving too much air but that seems unlikely. It it was you would be blowing loads of air out of your engine breather, leaking oil, etc...