1997 P38A DT Overheating

Hi everyone and happy new year, if we're still doing that.

About a week ago I was driving the P38a Diesel around all day long and then had to go on a run up north in it. I got about as far as Derby, which is and hour and half from home when I stopped for a coffee. Coming back out of the services with coffee in hand I notice a steady flow of coolant streaming down to a much bigger puddle of coolant on the floor under the car. I moved the car to somewhere in the services that I could take a closer look without being a nuisance to anyone only for the temperature gauge to rise into the red and the red light to come on.

I gave it a chance to cool, and then topped up with tap water and bled the system through the expansion tank neck with the heaters on, and then drove home with the heater on full, but it didnt overheat again that day. Since then, ive done a drive to Coventry and back which is about 20 miles each way, and the car didnt overheat. This morning though ive just driven to the village shop, which is about 3 miles away and arrived with the car overheating again, but on the three mile drive home it wasn't overheating.

Does anyone heave any ideas whats going on before i go out there and start checking coolant pipes?..... and godforbid order another new cylinder head...... that engine is like Triggers broom these days.

Where was the coolant leaking from?
Water pump is a possibility, plastic impeller ones can be unreliable plus they are cheap and easy to replace

I seem to remember putting a good quality WP on it... probably Quinton Hazell knowing me.... but that was about 2015...

The coolant was coming out through the expansion tank.

Have you checked the water pump bearings as well? I've had a clients quentin hazel water pump bearings fail after two years!!
There was excessive play...
Also check when starting from cold that the engine fan roars and then goes quiet.
A known technique is to try and stop the fan when the engine is hot with a news paper. If the fans stops easily it could be tired. At speed the airflow through the rad is enough to keep the temps down. Short low speed journey's don't produce enough airflow, this is were the fan steps in.

Assuming the fan still roars on startup I would fear a cracked head. However, it could be air getting in somewhere, the heater matrix o-rings are the prime suspect (wet carpet on side of transmission tunnel) but check the hoses to the rad too.

Duff viscous fan.

When’s last time you checked ancillary belt and tensioner?
If you get that worried about head issues sniff test is easy enough. There’s plenty of simple things to check it could be first so I wouldn’t worry too much just yet

Viscous fan was replaced this time last year. Can't remember what make off the top of my head but I know I had the choice of a Sh*tpart one for £40 or this one for nearly £200.... So I had the dear one.

I know when I've had cracked head before (twice now ) they tend to just pressurize the coolant almost immediately and that's not happening here. On faster roads, as you say the temperature seems fine....... actually I should mention that it seemed a little too cool on occasion...... would that be a dicky thermostat?

Just had a look at it this morning and my findings so far are thus:

No visible coolant leaks with engine off.
One weep between rubber hose and (aluminium?) pipe where heater pipes pass through bulkhead and significant staining of coolant on camshaft cover immediately adjacent to those heater pipes.
With engine warm, viscous fan will come to a stop by placing a magazine against the fins. Doesn't stop immediately though, just takes some pressure before it will come to halt.
Fan runs all the time.
No obvious "fan roar" on start up, although id like to see an example of that on another vehicle.
About 3/4 to an inch of deflection on the belt between the two upper most pulleys.
Belt in good condition. That was replaced this time last year.
No soggy carpets inside the vehicle.
No pressurizing of coolant. The car has been left running outside the house for the last hour or so, so its nice and warm, the thermostat is open, ive topped up and bled the coolant and the coolant level stays where it should.
With the system bled, the temperature gauge its sitting on the cool side just below dead upright. In all the time ive had this car ive always known the gauge sit bang on dead upright.
Idler pulley, adjacent to the alternator, feels smooth enough but ive known better.
Tensioner pulley feels very iffy.
Horrible ticking sound from front end of engine with engine running. Whatever that is, it clanks to a halt when engine is turned off.
With the drive belt removed, the water pump feels smooth running with no end float or play.

I can see a shopping list building up already but what causes you the most concern out of that lot?

If you can stop the viscous fan with the engine up to temperature, it's fecked.
Bin the viscous fan and fit my aircon fans mod, assuming the car has aircon or use my mod and fit an aftermarket fan. Much more reliable than the P38 viscous fan, I run 2 with no viscous fan.
Fix the leak as that will cause loss of pressure resulting possibly in localised boiling of the coolant.

Yep sounds like fan they should be loud and roar like a tank when first started then go quiet but roar again when hot and needed, they will turn all the time they never stop.

Cheers DT. My car has aircon but its never been charged in the 13 years ive owned the car and ive no idea when those two fans last turned. Where will I find your mod? Just did a quick google but all is three references to people sending you their email addresses... do you still have mine? Id like a copy of your instructions, please.

jimllshiftit said:

Cheers DT. My car has aircon but its never been charged in the 13 years ive owned the car and ive no idea when those two fans last turned. Where will I find your mod? Just did a quick google but all is three references to people sending you their email addresses... do you still have mine? Id like a copy of your instructions, please.

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PM me with an email address and I will send the info. The fans are probably OK but replacements can be found in breakers. Sort the aircon out, it helps keep the electronics dry especially in winter.

Get a bar or screw driver behind the inner crank pulley and check for movement. These can break the rubber band inside and will come loose. They can't fall off completely as the front aircon pulley will stop it falling off completely. If left the little tangs on the pulley innards will shear and then you'll lose all drive to the water pump and alternator.

jimllshiftit said:

Just had a look at it this morning and my findings so far are thus:

One weep between rubber hose and (aluminium?) pipe where heater pipes pass through bulkhead and significant staining of coolant on camshaft cover immediately adjacent to those heater pipes.


I can see a shopping list building up already but what causes you the most concern out of that lot?

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That sounds like a place air could get in. Those are the aluminium pipes that feed the heater matrix. Should be held in a rubber grommet.

Datatek said:

If you can stop the viscous fan with the engine up to temperature, it's fecked.
Bin the viscous fan and fit my aircon fans mod, assuming the car has aircon or use my mod and fit an aftermarket fan. Much more reliable than the P38 viscous fan, I run 2 with no viscous fan.
Fix the leak as that will cause loss of pressure resulting possibly in localised boiling of the coolant.

Click to expand...

It should only lock up when hot. That means giving it some revs while standing, especially in this cold weather. Normal operating temperature you should be able to stop it with a newspaper unless it has seized.

Cheers DT. Info received.

The fan is certainly harder to stop when the car has warmed up but I can still stop it if I want to.

What's the replacement for the crank pulley? I guess that's a damper that fails... Is there a rigid one available? I put one of those on my Cooper S and that goes much better now

Grrrrrr said:

It should only lock up when hot. That means giving it some revs while standing, especially in this cold weather. Normal operating temperature you should be able to stop it with a newspaper unless it has seized.

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As I said "if you can stop the fan with the engine up to temperature, it's fecked"

jimllshiftit said:

Cheers DT. Info received.

The fan is certainly harder to stop when the car has warmed up but I can still stop it if I want to.

What's the replacement for the crank pulley? I guess that's a damper that fails... Is there a rigid one available? I put one of those on my Cooper S and that goes much better now

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A solid crank damper is not a good idea, it's there for a reason, to absorb harmonic vibrations that could damage the crank.

jimllshiftit said:

Cheers DT. Info received.

The fan is certainly harder to stop when the car has warmed up but I can still stop it if I want to.

What's the replacement for the crank pulley? I guess that's a damper that fails... Is there a rigid one available? I put one of those on my Cooper S and that goes much better now

Click to expand...

The solid damper won't change performance it just shocks the crap out of the belt and it's accessories