TD5 Down on Power After Head Gasket Repair

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rickead2000

Member
Posts
53
Hi,

I hope someone might be able to give me a few pointers or know what might be the cause for my Disco's sudden loss of power.

I've a 2002 (pre-facelift) TD5 disco auto which lost coolant and overheated, resulting in the head gasket failing. It's covered 125,000 miles. I stopped the engine as soon as I saw the temperature gauge rise - although the needle went from "normal" to "hot" in about 10 seconds! The engine didn't run rough or show any problems at the time.

After fixing the coolant leak (split hose) and refilling the system, I did drive it around for a week or so afterwards; it drove fine and performance was normal and there were initially no signs of any issues. However occasionally I would hear some gurgling noises from the engine bay and the temperature gauge would start to rise again. Having looked inside the coolant header tank when it was running I could see gas bubbles rising and so assumed the head gasket had gone and booked it in to a local independent.

They agreed the head gasket had gone and also recommended the head was sent off to be skimmed. The garage also offered to blank off the EGR whilst they had things in bits for a nominal cost. Both of which were done.

Here come the problems - after everything was put back together, it had seemingly lost 80% of its power. The engine started fine and ran, revved and idled smoothly, but it was almost impossible to exceed 25mph; and would take ~30s to get there. It wasn't just a bit slow, it was unsafe to be on on a road.

Over the next 5 weeks, the garage say they checked and tried everything, including a new MAF, but could not pinpoint the cause or fix it. They finally said (by process of elimination) the ECU must have gone bad. As a result, they had it re-mapped with the most powerful mapping possible; this improved performance to a just about safely drivable level, but I would say still only around 50% of what it was pre-head gasket replacement.

The engine still starts immediately - often only 1 or 2 turns. It runs smoothly and sounds normal; it's just there's absolutely no "grunt". On a steep hill it's impossible to get above 30mph and the engine doesn't seem to want to rev past ~2800. I can floor the throttle and the auto box will shift down, revving up to just over 3000; but other than making a lot of noise doesn't really assist.

Is it feesible a duff ECU could cause this (and replacing the head gasket caused it to go bad)? Wouldn't a bad ECU not accept a new map or at least cause the EML to come on? I've also plugged in an OBD2 reader and get sane/accurate readings for the limited sensors available (throttle position, RPMs etc..)

-- I had the notorious wiring loom replaced ~20,000 miles ago due to oil ingress causing a misfire
-- I've unplugged the MAF sensor in case this was still bad as I believe this should cause the engine to go into a "default" mode. This made no difference (also no EML in this case either??).
-- Could the blanking off the EGR have been done incorrectly causing the issue? Anything I can check here?
-- Air filter is brand new and not blocked
-- I can hear the fuel pump pressuring and running when ignition is on
-- There's no slip in the auto box and the TC locks up as it used to in the rare instance I can get it to 50mph! I've not managed to get it past 70mph since the problem started.
-- It's worth re-iterating that the car's performane/power was perfectly as normal with a blown gasket; the low power problem happened immediately and suddenly at the time it was "fixed"
-- There are no warning lights on the dash at all
-- I can't hear any air whoosing (leaking) and the intercooler doesn't look obviously ballooned or cracked. Turbo hose looks solid with no cracks.

It's almost as though there's no turbo boost at all, there's no surge at higher revs at all. I have an air pressure meter arriving over the next few days which I'll splice into the feed to the actuator and see if/what boost pressure there may be to the actuator. I've read a few posts that suggest the actuator could have failed and isn't opening the waste valve, thus the engine is detecting an overboost and limiting power. However, the same posts say this is a very common problem on the TD5, and so I would have assumed it's something the garage would have already tried?!

Is there anything else I can do (being a very novice mechanic!) to try and hone down on the issue? I can obviously take it to another garage and ask them to investigate, but I don't fancy the potential of racking up ££££ of diagnostic labour charges on a car with a limited value.

Thanks in advance for any help anyone can offer!
 
Last edited:
I would tend to agree lynall.... However having had the car for a total of 7 weeks including the original head gasket fix, the garage were at a loss and said they didn't know what else to try. Short of a new ECU which they wanted about 1500 quid fitted.

After 7 weeks I just wanted the car back (plus they'd said there was nothing else they could do), so paid them for the work done minus any diagnostics and got the car out of there.

They'd told me they'd tried swapping in an ECU from a td5 defender of the same age to try and prove the issue, but apparently that would just stall after a couple of seconds of running.
 
rickead2000 said:
I would tend to agree lynall.... However having had the car for a total of 7 weeks including the original head gasket fix, the garage were at a loss and said they didn't know what else to try. Short of a new ECU which they wanted about 1500 quid fitted.

After 7 weeks I just wanted the car back (plus they'd said there was nothing else they could do), so paid them for the work done minus any diagnostics and got the car out of there.

They'd told me they'd tried swapping in an ECU from a td5 defender of the same age to try and prove the issue, but apparently that would just stall after a couple of seconds of running.
Click to expand...

I do not know enough about the td5, but would guess the security system was not hpapy with the defender ecu and that was why it switched itself off.

Listen to what James said above and check the timing of the camshaft (check yourube for videos) try and think logically, and ask yourself, what have the mechs removed and refitted that could be causing the issue?
Fuel lines damaged/kinked/fitted wrong?
Did they remove the injectors?
Manifold gaskets fitted correctly?
Pop the rubber trunking off and check the turbo spins/damaged?
Maf/Map/crank wiring okay?
Ecu plug have any oil in it?
Any codes?
Never assume any work has been done correctly, not a slur on the garage, but people make mistakes simle as.

Timing video,
 
rickead2000 said:
Hi,

I hope someone might be able to give me a few pointers or know what might be the cause for my Disco's sudden loss of power.

I've a 2002 (pre-facelift) TD5 disco auto which lost coolant and overheated, resulting in the head gasket failing. It's covered 125,000 miles. I stopped the engine as soon as I saw the temperature gauge rise - although the needle went from "normal" to "hot" in about 10 seconds! The engine didn't run rough or show any problems at the time.

After fixing the coolant leak (split hose) and refilling the system, I did drive it around for a week or so afterwards; it drove fine and performance was normal and there were initially no signs of any issues. However occasionally I would hear some gurgling noises from the engine bay and the temperature gauge would start to rise again. Having looked inside the coolant header tank when it was running I could see gas bubbles rising and so assumed the head gasket had gone and booked it in to a local independent.

They agreed the head gasket had gone and also recommended the head was sent off to be skimmed. The garage also offered to blank off the EGR whilst they had things in bits for a nominal cost. Both of which were done.

Here come the problems - after everything was put back together, it had seemingly lost 80% of its power. The engine started fine and ran, revved and idled smoothly, but it was almost impossible to exceed 25mph; and would take ~30s to get there. It wasn't just a bit slow, it was unsafe to be on on a road.

Over the next 5 weeks, the garage say they checked and tried everything, including a new MAF, but could not pinpoint the cause or fix it. They finally said (by process of elimination) the ECU must have gone bad. As a result, they had it re-mapped with the most powerful mapping possible; this improved performance to a just about safely drivable level, but I would say still only around 50% of what it was pre-head gasket replacement.

The engine still starts immediately - often only 1 or 2 turns. It runs smoothly and sounds normal; it's just there's absolutely no "grunt". On a steep hill it's impossible to get above 30mph and the engine doesn't seem to want to rev past ~2800. I can floor the throttle and the auto box will shift down, revving up to just over 3000; but other than making a lot of noise doesn't really assist.

Is it feesible a duff ECU could cause this (and replacing the head gasket caused it to go bad)? Wouldn't a bad ECU not accept a new map or at least cause the EML to come on? I've also plugged in an OBD2 reader and get sane/accurate readings for the limited sensors available (throttle position, RPMs etc..)

-- I had the notorious wiring loom replaced ~20,000 miles ago due to oil ingress causing a misfire
-- I've unplugged the MAF sensor in case this was still bad as I believe this should cause the engine to go into a "default" mode. This made no difference (also no EML in this case either??).
-- Could the blanking off the EGR have been done incorrectly causing the issue? Anything I can check here?
-- Air filter is brand new and not blocked
-- I can hear the fuel pump pressuring and running when ignition is on
-- There's no slip in the auto box and the TC locks up as it used to in the rare instance I can get it to 50mph! I've not managed to get it past 70mph since the problem started.
-- It's worth re-iterating that the car's performane/power was perfectly as normal with a blown gasket; the low power problem happened immediately and suddenly at the time it was "fixed"
-- There are no warning lights on the dash at all
-- I can't hear any air whoosing (leaking) and the intercooler doesn't look obviously ballooned or cracked. Turbo hose looks solid with no cracks.

It's almost as though there's no turbo boost at all, there's no surge at higher revs at all. I have an air pressure meter arriving over the next few days which I'll splice into the feed to the actuator and see if/what boost pressure there may be to the actuator. I've read a few posts that suggest the actuator could have failed and isn't opening the waste valve, thus the engine is detecting an overboost and limiting power. However, the same posts say this is a very common problem on the TD5, and so I would have assumed it's something the garage would have already tried?!

Is there anything else I can do (being a very novice mechanic!) to try and hone down on the issue? I can obviously take it to another garage and ask them to investigate, but I don't fancy the potential of racking up ££££ of diagnostic labour charges on a car with a limited value.

Thanks in advance for any help anyone can offer!
Click to expand...

Yuo may need to get proper diagnostics done, via a Foxwell/Nanocom/Hawkeye, although you may get away with OBD2 reader as it is engine prob.

I wouldn't worry about the ECU unless someone dropped it. they wouldn't have had to disturb it much to take the head off and put it back on.
If you just stuck a new one on ,and it even started, you was lucky as they aren't plug and play, the BCU needs to be "woke" to the change of ECU and the correct injector codes put into the ECU.
Could it be that it was skimmed too much? :eek:
Does sound like fuelling/timing.
 
lynall said:
I do not know enough about the td5, but would guess the security system was not hpapy with the defender ecu and that was why it switched itself off.

Listen to what James said above and check the timing of the camshaft (check yourube for videos) try and think logically, and ask yourself, what have the mechs removed and refitted that could be causing the issue?
Fuel lines damaged/kinked/fitted wrong?
Did they remove the injectors?
Manifold gaskets fitted correctly?
Pop the rubber trunking off and check the turbo spins/damaged?
Maf/Map/crank wiring okay?
Ecu plug have any oil in it?
Any codes?
Never assume any work has been done correctly, not a slur on the garage, but people make mistakes simle as.

Timing video,
Click to expand...

+1^
 
NPG said:
+1^ (most definitely)

Do you see any excessive smoke or lights coming up on the instrument cluster which could indicate the auto trans is running in limp home mode ?
Click to expand...
He did say he wasn't sure about the dump valve actuator. (can't remember its proper name for the mo!)
But if the valve is free, the actuator is soundly mounted, there are 13 threads between the lock nutand the end of the threads and the actuator is actually working then that can be ruled out, i would have thought. When mine went into limp mode due to this problem, i don't remember any lights coming on at all. But memory is fallible, mine especially!)
 
Stanleysteamer said:
He did say he wasn't sure about the dump valve actuator. (can't remember its proper name for the mo!)
But if the valve is free, the actuator is soundly mounted, there are 13 threads between the lock nutand the end of the threads and the actuator is actually working then that can be ruled out, i would have thought. When mine went into limp mode due to this problem, i don't remember any lights coming on at all. But memory is fallible, mine especially!)
Click to expand...

I was referring to the possibility of the auto gearbox going in limp home mode but given the OP's attention to detail, it would be very unlikely not to have noticed the warning lamps coming on. He also says that the torque convertor locks up at 50mph which more or less rules out the gearbox.

Like you suggested, he needs to get an OBD readout of any logged DTCs and preferably live reading of the critical components like MAF, Injectors, Wastegate, etc. I'm also hoping that the ECM has the correct grades for the injectors as otherwise the engine will not go above 3000rpm.
 
Thanks for all the help - my Amazon delivery with the pressure gauge got delayed but should be here tomorrow. I'll get a boost reading over the weekend and try and check the timing. Failing that I'll see if I can get a proper diagnostic on a Nanocom or similar
 
When was fuel filter last changed?
Just thinking car been standing for weeks so maybe has fuel bug?
Is in tank pump running? and if so is it humming or noisy?
 
It was ok before the work, and now isn't, then whomever did the work has screwed up. My guess is the timing is out a couple of teeth.
Edited for being a goofball.:oops:
 
Last edited:
I had an issue with mine, injector seals were leaking, had diesel in the sump. And even though it was making the right noises at the lift pump, my tank fuel pump wasn't working correctly
 
Update....

Fitted the boost pressure gauge today, with a T piece before the waste gate actuator.

Under reasonably heavy acceleration it was boosting to pretty much bang on 1 bar. Flooring it pushed the boost the 1.2, which it never exceeded.

That seems to be what people are saying it should be at. Does that now effectively rule out the turbo and waste gate actuator from the puzzle?

I'll pick up a new fuel filter tomorrow, it can't hurt to change it and it's probably due; although the problem was sudden onset after the head gasket as opposed to gradually getting worse.

I'll try and tackle the timing this weekend.

When turning to ignition I can hear the fuel pump humming, although I seem to remember also hearing a higher pitch pressurising noise around the same time which I can't hear now; although that could be a fault with my memory.

The auto box definitely isn't going into limp (it's done that before and I know the M + S lights).
 
rickead2000 said:
Update....

Fitted the boost pressure gauge today, with a T piece before the waste gate actuator.

Under reasonably heavy acceleration it was boosting to pretty much bang on 1 bar. Flooring it pushed the boost the 1.2, which it never exceeded.

That seems to be what people are saying it should be at. Does that now effectively rule out the turbo and waste gate actuator from the puzzle?

I'll pick up a new fuel filter tomorrow, it can't hurt to change it and it's probably due; although the problem was sudden onset after the head gasket as opposed to gradually getting worse.

I'll try and tackle the timing this weekend.

When turning to ignition I can hear the fuel pump humming, although I seem to remember also hearing a higher pitch pressurising noise around the same time which I can't hear now; although that could be a fault with my memory.

The auto box definitely isn't going into limp (it's done that before and I know the M + S lights).
Click to expand...
Out of curiosity, how did your timing check turn out?
 
rickead2000 said:
Update....

Fitted the boost pressure gauge today, with a T piece before the waste gate actuator.

Under reasonably heavy acceleration it was boosting to pretty much bang on 1 bar. Flooring it pushed the boost the 1.2, which it never exceeded.

That seems to be what people are saying it should be at. Does that now effectively rule out the turbo and waste gate actuator from the puzzle?

I'll pick up a new fuel filter tomorrow, it can't hurt to change it and it's probably due; although the problem was sudden onset after the head gasket as opposed to gradually getting worse.

I'll try and tackle the timing this weekend.

When turning to ignition I can hear the fuel pump humming, although I seem to remember also hearing a higher pitch pressurising noise around the same time which I can't hear now; although that could be a fault with my memory.

The auto box definitely isn't going into limp (it's done that before and I know the M + S lights).
Click to expand...
Hi i have experience exactly the same problem with mine ,dit you got yours fix and what was the fault ,i will be happy if you will share some of the results
 
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