Question on head gasket failure diagnosis

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jimmies

Member
Posts
58
Location
harrogate
I have a 2000 D2 TD5, I have been getting the limp mode becuase of high temp. I used to only get it on a week or so but yesterday it became worse

The story

So basically when coming home from work on a long 230 mile motorway drive, about 180 miles out it went into limp mode...I pulled over and let it cool for a min and was able to continue as the temp went back to normal. I kep a close eye on it as I progressed and as soon as it started to rise I would just back off/coast and generally it would drop back down after 5 to 10 seconds without the need to pull over. It happen around 15 times in all with one need to pull over as it happened on a hill and I lost too much speed.

The testing

I changed the coolant today and the old coolant was in good condition with no discolouration

The coolant pipes stay firm when engine is off and warm....and reduce as the coolant cools down....If there was a H/G blown, would they stay pressurised that long ??

The oil is in good condition with no milyness at all...just black

There is no white smoke or sweet smell in the exhaust

There are bubbles going into the expansion tank...these seem to push the coolant out when the cap is on....but the coolant comes right back when I take the cap off

Nanocom is not throwing up any errors at all...even after the limp modes yesterday !


Is there any other tests I can do to see what may be causing the limp modes......see also would sit fine at 80 for miles ...then it would just happen. It also seems to happen more on country roads

Cheers for any advise you may have
 
Thermostat could be the cause. Pump sounds ok if your getting return flow. The pipes do go firm, but you should still be able to squeeze them and yes, it should depressurize when cooled down, but you will get a small hiss when you remove the cap, not a large hiss.

Coolant level when cooled down should go back to normal spot too.

I would check that the radiator is getting warm when up to temperature, sounds alot like a stuck closed thermostat.
 
Last edited:
jimmies said:
I have a 2000 D2 TD5, I have been getting the limp mode becuase of high temp. I used to only get it on a week or so but yesterday it became worse

The story

So basically when coming home from work on a long 230 mile motorway drive, about 180 miles out it went into limp mode...I pulled over and let it cool for a min and was able to continue as the temp went back to normal. I kep a close eye on it as I progressed and as soon as it started to rise I would just back off/coast and generally it would drop back down after 5 to 10 seconds without the need to pull over. It happen around 15 times in all with one need to pull over as it happened on a hill and I lost too much speed.

The testing

I changed the coolant today and the old coolant was in good condition with no discolouration

The coolant pipes stay firm when engine is off and warm....and reduce as the coolant cools down....If there was a H/G blown, would they stay pressurised that long ??

The oil is in good condition with no milyness at all...just black

There is no white smoke or sweet smell in the exhaust

There are bubbles going into the expansion tank...these seem to push the coolant out when the cap is on....but the coolant comes right back when I take the cap off

Nanocom is not throwing up any errors at all...even after the limp modes yesterday !


Is there any other tests I can do to see what may be causing the limp modes......see also would sit fine at 80 for miles ...then it would just happen. It also seems to happen more on country roads

Cheers for any advise you may have
Click to expand...
The bubbles going into the coolant header tank are the most relevant clue, cylinder compression is getting into the coolant, much higher pressure than the 15psi or so of the coolant system, it displaces the coolant, the leak at this stage may be one way only, that is why you do not see the oil discoloration, if you continue to run the vehicle the "blow path" through whatever track it is taking, (head gasket to block joint into water jacket, crack through combustion chamber), will burn through more and rapid coolant loss and engine damage will ensue.
Try all the other avenues by all means but the compression leaking into coolant is the smoking gun.
 
Gazbo said:
The bubbles going into the coolant header tank are the most relevant clue, cylinder compression is getting into the coolant, much higher pressure than the 15psi or so of the coolant system, it displaces the coolant, the leak at this stage may be one way only, that is why you do not see the oil discoloration, if you continue to run the vehicle the "blow path" through whatever track it is taking, (head gasket to block joint into water jacket, crack through combustion chamber), will burn through more and rapid coolant loss and engine damage will ensue.
Try all the other avenues by all means but the compression leaking into coolant is the smoking gun.
Click to expand...

Missed the bubbles when I read the post, yes if there are alot of bubbles coming through as you say, then you may find a sniff test will work quite well to prove this point. Diesels are difficult to do a sniff test on, but sounds like it would be more reliable at the moment.
 
Had the thermostat out and tested it with kettle water and it seem to work properly.... Hit tap water would not activate it but kettle water did..... Looking like h/g:mad:
 
Just put new calipers, disks, pads, exhaust mid section, back box, serviced the prop with new uj's and its mot

Now have this to think about.... If it turns out to be the h/g not sure what I will do. I was happy doing the above. Not sure if a h/g is a step too far for my skills
 
Last edited:
If the h/g was gone why would you like the system stay pressurised.... Even in the morning after it was all cool it still had some pressure in it

Just looked through the papers and it had it's head skimmed and pressure tested 18 months ago, this was before it was owned by me. It was.009" thou bent and was milled

Firstly if it was previously repaired...can it be done again or am I looking at a potental new head?
 
Last edited:
jimmies said:
If the h/g was gone why would you like the system stay pressurised.... Even in the morning after it was all cool it still had some pressure in it

Just looked through the papers and it had it's head skimmed and pressure tested 18 months ago, this was before it was owned by me. It was.009" thou bent and was milled

Firstly if it was previously repaired...can it be done again or am I looking at a potental new head?
Click to expand...
The residual pressure after cooling overnight in the system is due to accumulated combustion gasses in the cooling system, a normally working cooling system works like this, as coolant heats it expands, creates pressure in the system, all flexible elements, hoses etc expand to accomodate the pressure up to the max relief pressure, about 15 psi, when the system cools, say overnight the liquid contracts thus fully relieving the pressure, the system "relaxes". The gasses and any air in the system is compressible thus the pressure remains, and as I said, the leak is probably only a one way flow at the moment, this will rapidly deteriorate to two way the more you use the vehicle.
The morning you crack the coolant tank cap and do not get a pressure blow out, you will know that the pressurised coolant is going into a cylinder, this can contaminate the engine oil, do not crank the engine if you detect this, a diesel engine will "hydraulic" with very little fluid in the cylinder, resuting in bent conrod, broken piston or at worse broken crank.
A head gasket replacement is not an enormous task and there are plenty of experienced professionals and d.i.y guys on here to guide you, also plenty of "how to's", just search, don't toss away a good vehicle just for the sake of a bit of challenging work.
 
Thanks for the reply

I will start a new thread on the journey of the head removal. One last question though - if my head was previously skimmed by. 009 thou (that's what the receipt says) if the head turns out to be warped again..... What's the a max that a head can be skimmed.
 
jimmies said:
Thanks for the reply

I will start a new thread on the journey of the head removal. One last question though - if my head was previously skimmed by. 009 thou (that's what the receipt says) if the head turns out to be warped again..... What's the a max that a head can be skimmed.
Click to expand...
Not too familiar with the Td5 particularly but I think it is overhead cam, when the head warps the camshaft bearing tunnels also misalign, when you bolt the head down after it has been skimmed, the cam being a straight machined forging has to sit into its supporting bearings which are out of alignment and no longer on their same centre, as yo fit the bearing caps you are applying a force to the camshaft which is slightly "bending" it which when rotating at its half engine speed will cause it to exceed its elastic limits and snap like what happens to a pice of metal when bent back and forth rapidly and so will break it. So there would be a skim limit which may be also applied to give valve clearance to the pistons also. Some of the more learned brothers and sisters here may be able to quote the limitations you are facing.
 
Thanks Gazbo - I figured the tolerances would be tight, I'm going to drop the company who did the skim a line and get their view on it too
 
well the head is off...the gasket looks undamaged - I've set up a thread in the TD5 engine section and any of your thoughts would be very welcome
 
I've had the head skimmed and I'm just getting all the bits together to re-assemble

y4mSKTMYHHSYAvRS4rbkcghN773jCcgwH_jFZxje2_Lvg7mcUL5jUjDhJd2sPE8R-6LhuwqYDC6JAWlEtZhD5eHU-M9kg0NSOnrd7G_HCf59jOGsXSzSqh0CFMQqESr_FAG0We23jj_vNnHvhTDUSvF7-WTBm9ZD1orLAzv8WczT0VAAKdqzO712PY1TuefB2rcGVz_P_lxnMrGssvG0NMXmg


can anyone tell me what this gasket and 6 washers are for please ?
y4m3p0FdqXHvleZefGrPkGw8q1FkKsBO9r5B_P7rdECTsgqBwhoVtnqmJIkU7xBeOvz4FwWersI5fAc03kgZ76IlPeGyk5JgBKLaLlAHHjqenRot1UVyW02mKjX4eGxdunQNupFu5if6kvAO7BzEG06MIiyZjh0VLQbivPOKT9AXfAWQbrfaquSX0f4O66DEFzTcM-twj0UX00OQekaJomJyQ
y4mcD8Kcd-k69CP7rUI0FuPpiUaBSCVfBkXKUc4eWoLm2qCCI5NcMQKq3eJYQmr7aejiGNcMGnni6jTKwjHE8ybeRT0hq0F-702bjuPgMBpqVSQ_Sx0vUSm--wbwIYxk3HJCU29fL6rNb9GMZr3HxwgtlNzs13zJuIugVrnsX8bepWl4Wkbm4mvjAM1GTw_QhFDhP6zoXrxdImh2sc9x6a3Jg
 
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