Hi Everyone,

I've been reading posts in this forum since so many years and its been a great help but I couldn't find any answers to my problem.
I have a 2000 DHS with 98,000 miles on it. The car is in perfect shape and all the things work just fine except for this overheating problem that has appeared last month.
I drive it almost everyday and the temperature needle never went above the half mark but last month it started to overheat a bit (next mark after the half) with the AC on but it would go to normal when i start driving & also goes back to normal when i rev it upto 2500 rpm on idling. the needle does not moves if the AC is off. Now heres the mystery, This happens only every 1-2 days and sometimes stays normal for 3-4 days.

Everyone is saying that its the Head Gaskets. The reservoir tank was slightly leaking coolant near the cap so I replaced it but the car started overheating too much after replacing it. I thought that an air pocket is causing this so I thought of bleeding it today (engine off> disconnected the 3/8" hose> blocked both overflow hose & 3/8" hose from the reservoir tank> pumped through the reservoir tank) there was too much air that came out and finally the coolant started to come out but the coolant stopped once I started the engine (with the cap on but still blocking the 2 hoses) the fans kicked in but the needle jumped upto the next mark after the half it came back to normal when I raised the revs upto 3000 but after sometime it went back & this time it dint came back to normal. one more thing, the rev has started to stay at 1500 & only comes down when i switch on the AC.

Now does anyone has idea what could be the problem?? I think the water pump is not functioning properly but how can I test it? why the 3/8" hose stopped pouring coolant when I started the engine?? Could it be the water pump tensioner??

Following are some tests and replacements I have done so far:

1. Checked and both fans are working fine at high and low speeds.
2. Replaced the thermostat & cleaned the radiator.
3. Replaced the reservoir tank and the cap.
4. Got the water pump checked, The mechanic says it works fine but i doubt it.

NOTE: The needle never went beyond the first mark after the Middle/Half mark...NEVER

I really need to fix this but I really dont think that the Head Gaskets are blown, It would be very helpful if any of you could share your experience with me.

Thanks,

Dehlawi

 

ok first question are u losing coolant????
if not then u dont have a leak.

second thing if the weather has been warm, temp will vary a bit sometimes the gauge is not as accurate as u think , if u can have a scanner read the actually temp may help u out.

if u have a nice breeze blowing through the motor it will keep it cool , if stop light and go runs a little warmer we can it dead air ,( no air flow)

 

No, I'm not losing any coolant and there are no leaks...

the temp here is around 35-40 degrees Celsius and where can i get a digital scanner?



Thanks

 

actually u need someone with a tech2 much easier. but i forgot to mention the a/c puts a load on the motor as well , it will force temp a little higher while at idle or vehicle not moving

 

a couple of questions .. just asking the general questions .. i'm not so familiar with this engine.

- have the radiators been checked for cooling fins obstructions, damage, etc
- did the coolant get replaced with proper mix?
- any chance that there remains air in the system after replacing stat?
- is the engine clean of oil buildup?
- has the AC been serviced properly? making sure that is not overfilled and overloading the engine?
- the idle issue is probably connected with the TPS (failing? overcompensating? not sure its designed to compensate, maybe GMTECH has this answer) .. AC brings it down probably by loading the system .. hmmmm ... read item above.

by the items i highlighted, sounds like there is a connection between the AC compressor and the rise in temp and/or something is sticking/jamming in the cooling system/AC system ..

also, i agree - if you are not losing coolant there is no leak and you need to find out what the real coolant temp is ...

.

 

check the purge line might be blocked

 

@ Stomper: Thanks for ur concern, read the the following comments:

- have the radiators been checked for cooling fins obstructions, damage, etc
Yes, it has been checked, seems to be working fine.

- did the coolant get replaced with proper mix?
It was but now its just water after the Radiator shop checked the water flow.

- any chance that there remains air in the system after replacing stat?
I dont think so because the car performed well for 2 weeks after replacing the thermostat.

- is the engine clean of oil buildup?
How do I check this?

- has the AC been serviced properly? making sure that is not overfilled and overloading the engine?
I replaced the compressor & the bottle 3 months ago but the heating problem just started about 3 weeks ago.

- the idle issue is probably connected with the TPS (failing? overcompensating? not sure its designed to compensate, maybe GMTECH has this answer) .. AC brings it down probably by loading the system .. hmmmm ... read item above.
I think it is the TPS.. will replace it after getting it checked on Saturday.

Thanks

 

Heres what I did today:

Took the car to this radiator shop and he checked the radiator flow, there was too much dirt and rust in the hoses and he cleaned it all up.
the flow was good though, now we kept the car started with AC on for about 1 hour and the temp needle stayed on the 12 o'clock mark.

Then i drove it back home (about 6 kms) it moved to the next mark a lil bit at the traffic light but then came back to normal in a min.

Now I went out after 4 hours and it was normal for about 40 mins and then the needle started to move to the next mark after the middle, I turned off the AC and then the needle started to move from 12 o'clock to the next mark & then back to normal even while driving (40-60 mph) and it kept on doing this..

Now is there any way to check if the Head Gaskets are gone? I need to be sure before spending $2000 on this job.


Thank you all so very much

 

I am having very similar problems with my 2001 DHS. I changed the water pump thermostat but am unsure how to bleed the system. My water is not flowing sufficiently and is backing up at the reservoir. I can add water and it will come out of the over flow valve while I am driving. So when I check it it is empty. I was to my exhaust is mixing with my water which is why I am not seeing the water. I am not sure I am about to rip the heads out myself and have them pressure tested. Please tell me ur results I am anxious to find out. The only thing is mine heats up to the second line after the middle and will flop all the way to the hot mark. Sorry to post my problem on ur post but its the almost the same problem.

 

after your next drive put cardboard on the floor to make sure no leaks, also open the hood and try and smell, see if u smell a sweet coolant .

a/c will force temp higher at idle but once going because of the fans r running cools the engine back down

for the idle being so high at time as stomper said check the iac, but also clean throttle body and check air filter, also look for vacuum leaks