Thread: 1999 P38 - Overheating periodically

Originally Posted by TheTree

I meant to add this as well!

When the beast is at normal temperature and with the engine running, feel the hoses and see if they are hard

Steve

Firstly, just replaced coolant cap and S hose leading from coolant as this was balloting when hot.........

For the most part, no the hoses are not hard..I can squeeze the larger hose going directly into the radiator all the way

A few questions:
Does it get hot when driving at speed or at a standstill?
Does your expansion tank/coolant reservoir rumble or have bubbles in it?

A handy little thing to have is a OBD2 ELM27 device to plug into your diagnostic port and then download a handy little app called Torque. You can then read the exact temperature that the ECU reads from the sensor. Better than the dumb gauge on the cluster.

From experience I can say that your overheating coolant was at least 115deg which builds up anywhere between 15 to 20 psi of pressure.

If you have bubbles, a hard radiator hose or a rumbling bubbly coolant tank, you have combustion gases in the cooling system.

You can have a brand new radiator, water pump, fans, thermostat and hoses etc but you're wasting your time and money if you have combustion gases getting into the coolant.

It will only get worse. I'd be taking off the heads and checking the old head gaskets and also the heads for warpage. In addition, it's likely you have a slipped liner in your block.

Okay had engine running at normal temp (mid way point)...hoses are soft including main hose going into radiator i.e. I can squeeze them no problems....

For your interest..just replaced coolant cap and S hose

There is a test for exhaust in the coolant, my local workshop did one for me pretty cheaply.

Might be worth doing to confirm that the heads etc are all OK

Steve

Originally Posted by TheTree

I meant to add this as well!

When the beast is at normal temperature and with the engine running, feel the hoses and see if they are hard

Steve

Originally Posted by banarcus

A few questions:
Does it get hot when driving at speed or at a standstill?
Does your expansion tank/coolant reservoir rumble or have bubbles in it?

A handy little thing to have is a OBD2 ELM27 device to plug into your diagnostic port and then download a handy little app called Torque. You can then read the exact temperature that the ECU reads from the sensor. Better than the dumb gauge on the cluster.

From experience I can say that your overheating coolant was at least 115deg which builds up anywhere between 15 to 20 psi of pressure.

If you have bubbles, a hard radiator hose or a rumbling bubbly coolant tank, you have combustion gases in the cooling system.

You can have a brand new radiator, water pump, fans, thermostat and hoses etc but you're wasting your time and money if you have combustion gases getting into the coolant.

It will only get worse. I'd be taking off the heads and checking the old head gaskets and also the heads for warpage. In addition, it's likely you have a slipped liner in your block.

Yes, overheats at speed, not standstill....and
Yes I can hear the coolant reservoir rumbling through the dash especially when its about to overheat.

By the Way...just had a test at the local mechanic...confirmed that combustion gases are in coolant as testing unit turned yellow from blue.

You will at the very least have one, maybe two blown head gaskets around the water jacket adjacent to the rear cylinders. Hopefully you haven't got any slipped liners.

Hi

I'm not sure how involved you want to get but one thing you can do is to purchase a borescope camera (cheap off ebay) and inspect each cylinder through the spark plug hole

This can often provide more info as to the nature of the issue.

Steve

Originally Posted by TheTree

But these periodic episodes sound weird.

Not to me. I went through exactly the same problems with mine in the early days of ownership - before slipped liners were well known.

We tested for exhaust gas in the coolant. Nothing.

We pulled the heads thinking head gasket problem. Nothing wrong there but we did a minor rebuild then (new cam, lifters, valve guides, etc.).

This intermittent sudden boiling went on for a long time before I bought a secondhand engine and fitted it.

Eventually, I had the original engine fitted with tophat liners and refitted it. That's what's in the car now.