Overheting

On my 4.0 P38 2001 I have just put on a new exhaust, 2 new tyres, new front crank seal and serpentine belt. First time out it overheated and does so each time I use it. Can leave it ticking over on drive and it won't overheat. Under load it will...can't see how the jobs I did can cause this.
It's losing water somewhere. Exhaust is clear, oil is normal although a bit of steam from oil cap, no signs of leaks.
All advice appreciated.
Cheers.

Did you remove any part of the cooling system to do the jobs?
Thinking maybe an air lock somewere?

Daft question but easy to do,you sure you put the belt on the right way and the water pumps erm pumping?

Only part of cooling system removed was top hose to easy removal of fan
Not sure if I could have put belt on wrong?back side of Belt over smooth pullies and grooved side over grooved pullies. Looked ok?

Checked the belt and it looks OK, was hoping it was something that simple...

Compression check first, and maybe a sniff test on the coolant. Just cos the oil looks clean doesn't mean the head gasket isn't leaking, it could be split between cylinder and water gallery.

OK,thanks.
What am I looking for in a sniff test ...exhaust kind of smell?

Steve Ashworth said:

OK,thanks.
What am I looking for in a sniff test ...exhaust kind of smell?

Click to expand...

No you wont be able to smell it yorself
A sniff test is a nickname for a test mecanics do were basicaly thay Put a special fluid in glass bulb and seal it tight over your expantion tank then pump the "fumes "of the water through it.
If the fluid changes colour therse carbon monoxide presant and the only way that can get into your water is through a leaking geadgasket

I see, it's not something I can do?

No but i dont think a garage would charge much

Steve Ashworth said:

I see, it's not something I can do?

Click to expand...

UNIVERSAL BLOCK TESTER KIT FOR GASKETS & CYLINDER HEADS PETROL / DIESEL BT500 | eBay

Found my compression gauge. Never actually used it. Is it best to remove all plugs before testing or one at a time. Done some googling but conflicting advice?
Which is best on P38?
Cheers

all plugs full throttle

Not sure how on the P38, but best to disable the coils....on a older coil ignition car, you just ground the HT lead to the centre of the dizzy.....not sure how to do it on a coil pack vehicle!

It has coil pack, guess I car remove a fuse/relay?

Done compression test and got following results,front to back

Drivers side. Pass side
145. 142
142. 140
148. 140
140. 138

Not a great deal of variation? Are these readings OK or not?

Cheers

Don't seem to bad....a variation of about 10% between values should be investigated,

A good reading should be between 140-160, so yours are on the low side of OK....

Thanks, what else could cause overheating?
Just been for a drive and it didn't overheat.
Is there a way to purge air locks?
Cheers

Aaagh, false hope...just started overheating again.
Don't know where to look now.

I don't like to be a doom-monger but it could be a slipped liner....

Do a search for posts about it and research it...see if any other symptoms fit the bill